This PDF file contains the front matter associated with SPIE Proceedings Volume 13123, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

This talk will consider the future of metal halide perovskite (MHP) photovoltaic (PV) technologies as photovoltaic deployment reaches the terawatt scale. The requirements for significantly increasing PV deployment beyond current rates and what the implications are for technologies attempting to meet this challenge will be addressed. In particular how issues of CO2 impacts and sustainability inform near and longer-term research development and deployment goals for MHP enabled PV will be discussed. To facilitate this, an overview of current state of the art results for MHP based single junction, and multi-junctions in all-perovskite or hybrid configurations with other PV technologies will be presented. This will also include examination of performance of MHP-PVs along both efficiency and reliability axes for not only cells but also modules placed in context of the success of technologies that are currently widely deployed.

Solar radiation will be the largest single source of electricity in a low-carbon future. To maximise the potential of solar power, new materials will be needed to harvest and convert solar energy alongside existing photovoltaic technologies. Molecular electronic materials, such as conjugated polymers and molecules, can achieve photovoltaic conversion through a process of photon absorption, charge separation and charge collection. The materials are appealing because of the potential to tune their properties through chemical design and their compatibility with high-throughput manufacture. They are also interesting model systems for photochemical energy conversion because of their parallels with natural photosynthesis. Through a remarkable series of advances in materials design, the efficiency of photovoltaic energy conversion in molecular materials has risen from 1% to around 20% within two decades, surpassing most predictions. We will discuss the factors that control the function of molecular solar cells including the nature of the charge separating heterojunction, and the impact of chemical and physical structure on phase behaviour, energy and charge transport, light harvesting, and loss pathways. Finally, we will address the limits to conversion efficiency in such systems.

A next target in photovoltaic energy conversion can possibly be met by developing perovskite triple or even quadruple junction solar cells. These require developing stable perovskite sub-cells with bandgaps in the range of 1.8 to 2.3 eV, i.e., a range that has not received much attention so far. Guided by photocurrent spectroscopy and absolute photoluminescence spectroscopy, in combination with bulk and interface passivation strategies, tandem and triple junction solar cells with a power-conversion efficiency of 26% have been reached. Photoluminescence of individual sub-cells provides information on the internal voltage in each absorber layer and offers a detailed understanding of the performance-limiting components in the tandem solar cell following prolonged continuous operation.

Microcavity exciton-polaritons are bosonic quasiparticles that result from the hybridization of excitons and modes of a confined electromagnetic field in a regime known as strong light-matter coupling. Having a low effective mass, polaritons can undergo condensation, the macroscopic occupation of the lowest energy and momentum state. Two-dimensional (2D) perovskites are promising candidates for polariton condensation due to their high exciton binding energies, low non-radiative recombination rates and strong oscillator strengths. However, despite their optimal optoelectronic properties, there are no reports of room temperature polariton condensation in 2D perovskites and only one unreproduced report at low temperature. In this study, we systematically examine the interplay between the emission from the exciton reservoir and the population of the lower polariton. We gain insights on how the spectral features of the emission of 2D perovskites affect polariton relaxation and onto one of the mechanisms making polariton condensation challenging in 2D perovskites.

Bulk heterojunction organic solar cells (BHJ OSCs) potentially can offer low cost, large area, flexible, light-weight, clean, and quiet alternative energy sources for indoor and outdoor applications. OSCs using non-fullerene acceptors (NFAs) have garnered a lot of attention during the past few years and shown dramatic increases in the power conversion efficiency (PCE). PCEs higher than 19% for single-junction systems have been achieved, but the device lifetime is still too short for practical applications. Thus, understanding the degradation mechanisms in an OSC is crucial to improve its long-term stability. In this talk, I will discuss the degradation mechanisms in BHJ OSCs. We investigated the impact of different blend materials and device structures on the device stability. A combination of characterization methods such as solid state Nuclear Magnetic Resonance (NMR), resonant soft X-ray scattering (RSoXS), AFM, X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR) spectroscopy, and capacitance spectroscopy are employed to gain insight into the device degradation mechanisms. We propose strategies to improve the device stability.

In 2021 the IOPV-LAB (Indoor Organic Photovoltaic LABoratory) was created bringing together two laboratories from Aix-Marseille University (CINaM and IM2NP) and the company DRACULA TECHNOLOGIES (DT) to lift together the technical barriers to the development of OPV modules processed by ink jet printing dedicated to indoor (IOPV). Here we present our recent results of the IOPV-Lab towards the processing of high efficiency OPV modules with low environmental footprint as well as developing a standard for power conversion efficiency measurements under indoor light. We present the lab to fab transfer from highly efficient NFA based polymer blends using high band gap acceptors to ink jet printed solar cells. Furthermore, the stability of NFA based printed solar cells and modules will be discussed.

Commercialization of flexible perovskite solar cells (or PSCs) is prohibited by environmental instability and low mechanical robustness. We use glancing angle deposition (GLAD) at low substrate temperature to in-situ deposit nanopillar arrays (NaPAs) onto a flexible electrode for an assembly of flexible PSCs. The NaPAs are made of diverse inorganic materials, such as titanium, titanium oxides, tin oxides (functioning as electron transporting layers) and nickel oxides (serving as hole transporting layers). The as-grown NaPAs enhance light transmittance, facilitate light harvesting in perovskites, promote charge carrier transport and collection, facilitate the formation of large perovskite grains, prohibit perovskites from decomposition, and release mechanic stress. All these features cause large-area flexible PSCs to have PCE of >15%, small photovoltaic hysteresis, 10% degradation for approximately 800-hr storage, and 20% degradation by manual bending for around 400 times.

Flexible perovskite solar cells (PSCs) show promise for next-gen photovoltaics, but achieving stability remains challenging, especially between rigid and flexible substrates. This study optimizes flexible PSCs' stability and reproducibility by selecting substrates, refining cleaning processes, and enhancing interfaces. Evaluating various substrates for flexibility, roughness, and perovskite compatibility, a meticulous cleaning protocol removes contaminants, improving perovskite-adhesive interactions. Emphasis on buried interfaces minimizes defects and boosts charge transport. Results show improved PSC efficiency (15.2% to 19.7%) and cycle durability (130 to 850 cycles, bending radius 5mm, reaching T80). Closing the performance gap, these findings advance reliable flexible PSCs for portable electronics, wearables, and building-integrated photovoltaics.

Halide perovskites are a promising candidate for next generation energy-harvesting technologies owing to their excellent optoelectronic properties and low-cost solution processability. A striking difference between halide perovskites and conventional semiconductors (e.g., silicon) is the dual ionic-covalent bond nature within the anionic inorganic framework. This bond nature results in a mechanically soft and dynamically disordered lattice whose alteration affects the optoelectronic properties and the stability of these solids. Thus, metal-halide perovskites are particularly sensitive to variations in composition, fabrication and external stimuli that can induce strain in the material. The high magnitude of strain in halide perovskites is remarkable as they are one of the most fragile semiconductors, yet their resilience to adapt to stress is their most fascinating property. Understanding their crucial elastic properties for synthesis and device operation remains limited. We performed temperature- and pressure-dependent synchrotron-based powder X-ray diffraction of several lead-halide (3D) and double perovskites at low pressures (ambient to 0.06 GPa, similar to those experienced during manufacturing) to investigate their elastic properties in their ambient-pressure crystal structure. In this talk, I will show that we found common trends in bulk modulus and thermal expansivity, with an increased halide ionic radius (Cl to Br to I) resulting in greater softness, higher compressibility and thermal expansivity in both class of materials. For non-cubic systems, in which the elastic properties are anisotropic, we obtained axis-dependent compressibility. The A cation has a minor effect, and mixed-halide compositions show intermediate properties. Notably, thermal phase transitions in MAPbI3 and CsPbCl3 induced lattice softening and negative expansivity for specific crystal axes, even at temperatures far from the transition point. These results emphasize the significance of considering temperature-dependent elastic properties, which can significantly impact device stability and performance during manufacturing or temperature sweeps.

Lead and tin halide perovskites are currently under intense investigation for their potential applications in optoelectronics, due to their favorable and adjustable semiconducting properties. Despite the potential for widespread adoption in the industrial sector, dry deposition of perovskite films and devices remains a specialized area. Here we will examine the latest developments in the vacuum deposition of perovskite films, focusing on methods to manipulate their morphology and structure. Specifically, we will highlight the impact of factors such as composition, deposition rate, and substrate temperature on properties like luminescence quantum yield and recombination lifetime. We will also present a dry synthetic method to prepare powders and functional disks starting from raw chemical precursors. Lastly, we will show the use of these materials in solar cells and photodetectors.

Solar photovoltaic (PV) energy has been playing an increasingly important role in the world’s energy portfolio. It is becoming a key contributor to the global transition to decarbonized electricity generation. Lead (Pb) halide perovskites have attracted great attention in PV due to their outstanding optoelectronic and defect properties. The research of halide perovskite solar cells continues to boom with device energy conversion efficiency approaching that of single crystal silicon solar cells The discovery of the extraordinary properties enables its application in efficient single-junction and multi-junction solar cells. In this talk, I will present the advance in understanding the optoelectronic properties of halide perovskites. One of the most promising, yet not heavily researched approaches is to make tandem solar cells using materials that function well even when they are polycrystalline and defective. Recent advances with hybrid perovskite semiconductors and their potential use in tandems will be emphasized. The progress of low-voltage deficit in wide bandgap perovskite and its application in high-performance perovskite-silicon tandem solar cells will be discussed.

Metal Halide Perovskite (MHP) photodetectors exhibit remarkable potential as they combine high specific detectivities, fast response speeds, precise modulation of film optical properties, and seamless integration with read-out integrated circuitry. To attain such performances and maintain them requires an accurate design of charge transport layers. Here we demonstrate how solution processed organic-inorganic interlayers based on metal oxide nanoparticles and polymer mixes enable fast and sensitive visible MHP photodiodes, while warranting stability and pixel-to-pixel reproducibility superior to those of the individual materials. The talk will finish by providing an overview of a broader range of applications of MHP detectors for high and low energy radiation detection.

Organic retinomorphic sensors are particularly effective for motion detection, offering the advantage of in-sensor processing that can remove repetitive static backgrounds. In this study, we investigate the important impact of high-k dielectrics in promoting charge accumulation to increase the intrinsic photo-response of photo-sensitive capacitors within this promising framework. We demonstrate a retinomorphic sensor array to detect the motion of a sample moving at different speeds and directions. These proof-of-concept results represent a promising advance toward scalable integration of organic retinomorphic arrays to meet the growing demand for more efficient motion tracking systems.

Photovoltaics play a vital role in the transition to sustainable and green energy sources. However, conventional rigid and bulky solar cells fail to address the needs of emerging applications where mechanical compliance and high specific power are vital. In this regard, hybrid organic-inorganic halide perovskites attract significant interest owing to their outstanding mechanical and optoelectronic properties. In this contribution, we present transparent-conductive-oxide (TCO)-free and lightweight quasi-2D flexible perovskite solar cells incorporating arylamine organic cations with a champion-specific power of up to 44 W g-1 and an efficiency of 20.1%. Freestanding and unencapsulated flexible devices display admirable environmental stability and mechanical resilience. Rigid devices exhibit excellent operational stability, preserving above 97.2% of their performance after 1000 h of continuous operation at the maximum power point. Moreover, to show the feasibility and potential for upscaling, we demonstrated a photovoltaic module that enables energy-autonomous operation of a hybrid solar-powered quadcopter while constituting only 1/400 of the drone’s weight.

Understanding the chemical factors that dictate long term stability in metal halide perovskite thin films is critical in the optimization of fully commercialized printable energy conversion, display and optoelectronic platforms, X-ray detectors, and photodetectors. The origin of these instabilities has been associated with defects within the perovskite crystal lattice. This talk will discuss established (spectro)electrochemistry-based measurement science approaches to quantify the distribution and energetics of donor and acceptor defects in prototypical perovskite solar cell materials and at buried charge selective interlayers (i.e., hole transport layers). Connections to device performance, benchmarked with time-resolved photoluminescence measurements, will be shown. Results demonstrating the connection between defect quantification and durability will also be discussed in the context of activated corrosion of metal halide perovskites, as probed by dynamic near-ambient pressure X-ray photoelectron spectroscopy.

Understanding and minimizing non-radiative recombination pathways from contacts and interfaces is key to enhanced efficiencies in emerging solar cells. Non-radiative recombination in any form, i.e. trap-assisted, or surface recombination of minority carriers at the (wrong) electrode will inevitably lead to lower efficiencies. However, given the fast development of the efficiencies, the stability of both PSCs and OPVs is still not satisfactory. The challenge to suppress non-radiative recombination losses in OPVs and PSCs on their way to the radiative limit lies in proper energy level alignment and suppression of recombination from defects at interfaces, and contacts enabling increased effciencies and lifetimes.

Perovskite-based multijunction solar cells are cost-effective strategies to deliver power conversion efficiencies beyond the theoretical limit for single-junction solar cells. In this presentation, we address important factors limiting the performance and longevity of wide-bandgap perovskite solar cells and strategies to achieving record all-perovskite triple-junction solar cells. In addition, by connecting an all-perovskite tandem solar cell with a water electrolysis cell, we demonstrate a solar-to-hydrogen efficiency of 17.8%.

The emergence of nonfullerene acceptors (NFAs) has triggered a rapid advance in the performance of organic solar cells (OSCs), endowing OSCs to arise as a promising contender for 3rd generation photovoltaic technologies. Meanwhile, the ultimate goal of OSCs is to deliver cheap, stable, efficient, scalable, and eco-friendly solar-to-power products contributing to global carbon neutrality. However, simultaneously balancing these five critical factors of OSCs toward commercialization is extremely challenging. In this presentation, I will show the self-assembly strategy we developed to reduce the gap of high PCE, long-term stability, green-solvent-processibility, scalability, and low cost of OSCs and demonstrate our green-solvent-processable and open-air-printable OSCs with simultaneously simplified device architecture and enhanced PCE, shelf, thermal as well as light illumination stability. Further, I will present our recent results on the outdoor degradation mechanism study in top-performing systems. Finally, I will summarize our findings on enhancing the commercial viability of OSCs toward commercialized cheap, stable, efficient, scalable, and eco-friendly OSCs.

The increasing global demand for personalized healthcare technologies necessitates a new generation of wearable sensors that are high-performance, low-cost, and compatible with various platforms, including human organs. Low-temperature-processed hybrid and nanostructured materials enable such devices by allowing direct patterning onto 2D and 3D substrates through cost-effective printing processes. Their electronic and mechanical properties can be easily tuned through composition or morphology adjustments. In this presentation, I will describe how this material class facilitates novel wearable medical devices with unprecedented performance. Specifically, I'll focus on creating optical devices for noninvasive physiological measurements, including a high-gain high-speed photovoltage transistor for continuous vital sign tracking and a single-point spectrometer for multi-spectral photoplethysmography. Additionally, I will discuss our recent exploration of using quasi-two-dimensional Dion-Jacobson phase perovskites to achieve photonic structure-integrated light-emitting devices.

Specific emphasis in this talk will be placed on the development of see-through power windows via a new design of semitransparent organic solar cells (ST-OSCs), which allows for the efficient utilization of spectrum-engineered solar photons from the visible to infrared range with both energy generation and saving features.

To detect the band-specific optical signals used in many fields, it is necessary to develop spectrally selective photodetection. For such wavelength-selective photodetection or color discrimination, organic photodetectors (OPDs) can offer significant benefits as low temperature and solution processability, chemical versatility, and specific spectral detection range. However to avoid commonly used filters, the design of a narrowing approach that simultaneously achieves a selective detection range with a bandwidth of less than 50 nm and a spectral response of over 20%, remains a challenge. OPDs based on charge collection narrowing (CCN) principle can provide these features. Herein, we realize filter-free band-selective OPDs based on PM6:PC70BM blends as state-of-the-art. Fine adjustment over a bandwidth of 42 nm to be highly selective at 677 nm with a quantum efficiency of 48.4% under an inverse low bias of -2 V is reached. In addition, using a non-invasive and non-destructive encapsulation technique, we demonstrate that these OPD fully retain their high selective peak after 30 days storage in air.

We propose unique anodic nanostructures, consisting of hole-transporting polymers and self-assembled monolayers, to fabricate perovskite solar cells. The so-called, self-adaptive transport layer effectively reduced the loss of open circuit voltage and fill factor. The PCE value could reach 19.63% under 1-sun standard illumination condition. More importantly, the device exhibited high PCEs of 33.54% and 38.16% under illumination of indoor light sources at 200 and 2000 lux, respectively. This indoor PCE at 2000 lux is one of the best values for inverted perovskite devices. Furthermore, a very high efficiency of over 40% was also achieved after an optical enhancing layer was applied. Such indoor PCE at 2000 lux is one of the best values for inverted perovskite photovoltaic devices. Finally, the stability of the devices is also evaluated.

Metal oxide materials are crucial for efficient perovskite solar cells (PSCs) due to their stability and wide bandgap. We introduce a low-temperature intercalation method using p-type nickel oxide (NiO) with cesium carbonate (Cs2CO3) to enable bipolar charge transport in PSCs. The Cs2CO3-intercalated NiO serves as both hole and electron transport layers in inverted and conventional planar PSCs, enhancing electron extraction without compromising hole extraction efficiency. This approach achieves power conversion efficiencies of up to 12.08% and 13.98% for inverted and conventional planar PSCs, respectively, while also providing a potential route for tandem optoelectronics.

The OSC field has been revolutionized through the development of numerous novel non-fullerene acceptors (NFA). The device stability and mechanical durability of these non-fullerene OSCs is critical and developing devices with high performance, long-term morphological stability, and mechanical robustness remains challenging. We will discuss: 1) our current understanding of the phase behavior of OSC donor:acceptor mixtures and the relation of phase behavior and the underlying hetero- and homo-molecule interactions to performance, processing needs (e.g., kinetic quenches), and morphological and mechanical stability; 2) molecular hetero-interactions between the donor and NFA that are not always the geometric mean of the homo-interactions; molecular interactions that are relevant in understanding in rubber-toughening of OSCs with a SEBS additive; and 3) that ~50% of semi-conducting blends investigated so far exhibit re-entrant phase behavior. The results presented and its ongoing evolution are intended to uncover fundamental molecular structure-function relationships that will allow predictive guidance on how desired properties can be targeted by specific chemical design.

Energy transfer between materials in organic photovoltaics often assists energy transport to the site of free charge generation. Here we present a case where the opposite is true: dilute donor molecules sensitizing a fullerene matrix. We show via a combination of time-resolved microwave conductivity (TRMC), femtosecond transient absorption (fsTA), and photoluminescence excitation (PLE) spectroscopy that fast energy transfer from the donor to the acceptor ultimately results in charge transfer, but not photoconductivity. Instead, the excited states are lost as tightly bound charge-transfer states that do not subsequently dissociate to from free charge in this system. This behavior is caused by an asymmetry in the entropy associated with charge transfer in each direction and is well described by a model in which free charge generation is governed by a combination of entropic gain and competition between multiple Marcus-like charge transfer events to a distribution of distances.

The solar power conversion efficiencies of organic solar cells (OSC) have now increased up to 19%, closing the gap with inorganic and hybrid solar cells. The major breakthrough behind the rapid efficiency improvement is the development of non-fullerene acceptor molecules, replacing the traditional fullerene molecules as electron-accepting materials. Understanding the photophysical processes underlying these high-performance materials is crucial to OSC research. In this talk, I will present transient optical spectroscopy and structural analysis results on high-performance OSC blends based on state-of-the-art Y-type small molecule and polymeric acceptors. We find direct evidence that the interfacial D-A percolation plays a key role in suppressing interfacial charge recombination to enable efficient charge generation, and such morphology greatly improves the thermodynamic stability of the blend. Furthermore, we uncovered a new all-optical method for predicting the OSC performance of acceptor molecules, which will be a valuable tool for future material design and screening.

Conjugated hairy-rod polymers, which have emerged as promising photocathode materials for solar-fuel production, are comprised of stiff, low-entropy backbones and complex side-chain substitutions, which collectively affect assembly compared to flexible-chain materials. Here, we unravel the relationship between structural and electronic disorder in a model hairy-rod polymer, PBTTT. We identify a narrow electronic density-of-states (DOS) distribution with weak spatial variations in PBTTT, while the prototypical flexible-chain polymer, P3HT, features an energetically broad, spatially variable DOS. We assign this observation to the fact that PBTTT is structurally homogeneous due to its liquid-crystalline-like behavior, contrary to the structurally heterogeneous, semi-crystalline P3HT. This view is further supported by 2D electronic spectroscopy, which reveals that PBTTT features dynamic electronic disorder, vs. P3HT, which exhibits primarily static electronic disorder. Collectively, our work provides understanding into the disordered energy landscape in conjugated hairy-rod polymers, towards accelerated materials discovery for renewable energy technologies.

Considering the technical standards required for wearable electronics, such as mechanical robustness, the development of fully stretchable OSCs (f-SOSCs) should be accelerated. Concurrently, f-SOSCs offer an intriguing platform for testing the mechanical and electrical properties of new polymeric materials. This presentation will discuss key studies aimed at making each layer of f-SOSCs both stretchable and efficient, with an emphasis on strategies to simultaneously enhance the photovoltaic and mechanical properties of the active layer. I will outline material design strategies to enhance the mechanical robustness of the PSCs as well as their power conversion efficiencies (PCEs). These strategies include; i) incorporating a high-molecular weight polymer acceptor as a tie molecule into active layers, ii) developing new electroactive polymers consisting of hard and soft segments and iii) developing new materials that improve molecular miscibility in the donor-acceptor blends. With these contributions, the f-SOSCs achieving over 14% PCE and high stretchability have been developed.

Immense efforts in the flexible electronics field have led to unprecedented progress and to devices of ever increasing performance. Despite these advances, new opportunities are sought in order to widen the applications of flexible electronics technologies, expand their functionalities/features, with an increasing view on delivering sustainable solutions. We discuss here opportunities the use of multicomponent systems for, e.g., increasing the mechanical flexibility and stability of organic electronic products, or introducing other features such as self-encapsulation and more robust transport. We demonstrate the working principle of semiconductor:insulator blends, examining the different approaches that have recently been reported in literature. We illustrate how organic solar cells (OPV)s can be fabricated with such systems without detrimental effects on the resulting device characteristics even at high contents of the insulator.

For organic solar cells to be competitive, the light-absorbing molecules should simultaneously satisfy multiple key requirements, including weak-absorption charge transfer state, high dielectric constant, suitable surface energy, proper crystallinity, etc. However, the systematic design rule in molecules to achieve the abovementioned goals is rarely studied. In this work, guided by theoretical calculation, we present a rational design of non-fullerene acceptor o-BTP-eC9, with distinct photoelectric properties compared to benchmark BTP-eC9. o-BTP-eC9 based device has uplifted charge transfer state, therefore significantly reducing the OSC energy loss by 41 meV and showing excellent power conversion efficiency of 18.7%. Moreover, the new guest acceptor o-BTP-eC9 has excellent miscibility, crystallinity, and energy level compatibility with BTP-eC9, which enables an efficiency of 19.9% (19.5% certified) in PM6:BTP-C9:o-BTP-eC9 based ternary system with enhanced operational stability. Ref. Nature Communications (2024) In press

The properties of organic functional materials are determined by both their chain structure and the intermolecular interactions. Based on the basic concept of precisely controlling intermolecular interactions, we have developed a series of material systems with specific transport structures by controlling the arrangement and aggregation of organic optoelectronic molecules through the Cl∙∙∙S and Cl∙∙∙π interactions. In particular, we discovered a three-dimensional (3D) network structure in the model molecules with specific chlorine-mediated intermolecular interactions. We also systematically studied the effects of chlorine substitution position, number, and isomerism on the formation of the 3D network structure, which could provide the better molecular design strategy to achieve improved device performance. With the exciton diffusion distance exceeding 40 nm, those materials open a window for the development of quasi-planar heterojunction (Q-PHJ) devices. Compared with bulk heterojunction (BHJ) devices, Q-PHJ devices have a thermodynamically stable donor-acceptor bilayer structure, which can greatly improve device stability for coming practical applications.

The combination of donor (D) and acceptor (A) materials in organic solar cells (OSC) determines the corresponding D:A morphology in solar cells and the so-called golden triangle of OSC, that is, cost, power conversion efficiency (PCE), and stability. However, despite the recent advancement in OSC, determining the optimal material combination for industrialization is still a challenge. Herein, we unveil the optimal material combination that exhibits maximum industrial viability. Specifically, the industrial figure of merit (i-FoM) of 7 OSC categories is calculated and further analyzed, including small molecule donor (SMD):fullerene acceptor, SMD:non-fullerene acceptor (NFA), oligomer donor:NFA, terpolymer:NFA, polymer donor:NFA, polymer donor:polymer acceptor, and single-component materials. Since OSC is approaching wide-scale industrialization, our insights into the successes and challenges of these material combinations, particularly their PCE, photostability, and synthetic complexity (SC) index, offer guidance toward accelerating the industrialization of OSC.

To fulfill the promise of two-dimensional perovskites (2DPs) for high-performance optoelectronics, we used mechanical exfoliation to obtain n = 1 / n = 3 2DP-heterostructures and ultrafast techniques to characterize charge carriers’ dynamics at interface. In the presence of the heterostructure, we observe the suppression of excitonic-radiative recombination and the introduction of a fast decay channel for excitons (t < 2 ns) which explains more than 80% of the total photoluminescence decay. Such evidence can be explained through ultrafast electron and hole transfer at the heterostructure interface.

Among methods to synthesize perovskite nanocrystals, flow synthesis has demonstrated the possibility of overcoming batch-to-batch variability problems. This issue often occurs during synthesis using hot injection and ligand-assisted reprecipitation techniques. Microfluidic synthesis features high throughput, efficient heat transfer rates, as well as rapid and uniform mixing. In this work, we developed a portable fluorescence lifetime imager to study the physical and optical properties of perovskite nanocrystals during flow synthesis. The portable fluorescence lifetime imager was combined with a microfluidic synthesis platform. This setup acquired fluorescence lifetime in real-time during the synthesis process. Fluorescence lifetime provides PLQY of perovskite nanocrystals and their luminescence mechanism. In addition, the fluorescence lifetime of perovskite nanocrystals is determined by the spatial arrangement of the nanocrystals, synthesis parameters, fluorescence intermittency, etc. Perovskite is easily affected by environmental factors and then changes, so real-time measurement is essential. In order to control the size and shape of synthesized perovskite nanocrystals, we changed trace synthesis parameters (molar ratio of Cs, Pb, and halide precursors, reaction temperature, flow rate, and reaction time) of the microfluidic device. Meanwhile, direct fluorescence lifetime data from the microfluidic channel revealed synthesis results in real-time. As a comparison, all-inorganic cesium lead halide perovskite nanocrystals were synthesized in traditional batches and underwent post-processing, such as centrifugation, to obtain purified perovskite nanocrystals. We then used a custom-built frequency domain fluorescence lifetime system to measured and compared the purified perovskite nanocrystals and those from flow synthesis. It was shown that our microfluidic synthesis system mixed samples quickly and uniformly, and the real-time fluorescence lifetime data was a good indicator for uniformity of the synthesis results.

The double perovskite materials A₂SnCl₆ (A= Sr, K) demonstrate significantly enhanced stability compared to Sn²⁺ based perovskites, as well as promising optoelectronic properties including direct bandgaps. A₂SnCl₆ adopts a vacancy-ordered double perovskite structure featuring isolated [SnCl₆] octahedra, which contribute to a quantum confinement effect that enhances photoluminescence. The calculated structures exhibit a cubic phase with the Fm-3m space group, and their lattice parameters agree closely with reported values. All double perovskites exhibit mechanical stability. The band gaps of the perovskites vary depending on the A substitution from K to Sr. The total density and partial density of states provide insights into the variations in band gaps. The optical properties are determined through frequency-dependent dielectric functions, with optical absorption occurring in the visible range of 400-800 nm. Considering the stability, bandgap, and optical absorption properties, A₂SnCl₆ (A= Sr, K) emerges as a potential material for photovoltaic applications.

A fill factor (FF) in polymer solar cells has been less studied but should be understood in the photovoltaic parameters. The experimental FF is well explained for typical solar cells by an empirical equation with photovoltaic and device parameters such as series and shunt resistances, while it is not true for polymer solar cells. To investigate this discrepancy, we first analyzed FF by using an empirical equation for FF based on the equivalent circuit model. As a result, FF measured was in good agreement with that obtained by the empirical equation with parameters evaluated under illumination condition, but was not consistent with that in the dark condition. This finding suggests device parameters are dependent on illumination conditions. Thus, we next discussed the limiting factors of FF in terms of charge carrier dynamics in the three polymer solar cells. Specifically, two of the devices exhibited the significant decrease in FF down to 0.4 as the active layer thickness increased. On the other hand, the other device maintained a high FF of 0.6 even with a thicker active layer. To discuss this different dependence, we evaluated the recombination kinetics parameters by transient optoelectronic measurements. Interestingly, we found no significant difference in the recombination reduction factor, which was suppressed by two orders of magnitude compared to Langevin recombination for all the devices. With these kinetic parameters, the J–V characteristics were well reproduced for the high FF devices, but not for the low FF devices. In the latter devices, isolated domains, where charge carriers are not collected at the electrode, need to be considered. We further discuss the competition between charge collection and recombination and propose that for high FF to be achieved in polymer solar cells, it is essential that the mobility of the fast component exceed ~10⁻³ cm² V⁻¹ s⁻¹.

This investigation assesses the effect of different encapsulation materials and environmental conditions on ionic currents in methylammonium lead iodide (MAPI) thin films, which are essential for the stability of perovskite solar cells. Encapsulation types such as PMMA, MgF2, and SiO2 were examined under both air and vacuum conditions, complemented by an epoxy-sealed glass cover for extra protection. Employing the photo-electromotive force technique to analyze ion dynamics, findings indicate that environmental exposure and layer interaction profoundly influence ionic activity. While a single encapsulation layer falls short in protecting against environmental factors, combining SiO2 with an epoxy-sealed glass significantly improves MAPI film stability, albeit the epoxy layer alters ionic responses, underscoring the complexity in optimizing encapsulation for enhanced solar cell performance.

Self-assembled monolayers (SAMs) have emerged as promising hole transport layers (HTLs) in organic solar cells (OSCs). The compound 2PACz has demonstrated superior performance compared to the conventional PEDOT: PSS. The latter is known to have poor stability and can also suffer from weak interfacial adhesion energies, leading to delamination failures within the device stack. Our investigation is focused on the impact of SAMS on OSC performance, operational stability, and mechanical stability. We hypothesize that halogenation of 2PACz will enhance adhesion strength through electrostatic bonding. We have conducted a comparative analysis of a number of SAMs including Cl-2PACz, Br-2PACz, and MeO-2PACz. We explore their impact on adhesion through peel tests and DCB tests. We show that the use of 2PACz results in a threefold increase in peeling strength relative to PEDOT: PSS. Additionally, our OSCs exhibited nearly a 1% increase in PCE with Br-2PACz.

In this work, we report a lead-free MASnI3 perovskite photodetectors prepared by inverse temperature crystallization method. The surfaces of MASnI3 perovskite films are smooth and evenness. The MASnI3 perovskite photodetectors t has the highest photocurrent value in green light region among the five monochromatic light sources with a photocurrent of 1 uA at bias of 10 V. The advantage of this work is that the manufacturing process is relatively simple and safety, so it can be easily manufactured.

This study explores the use of elastomer additives to increase the mechanical reliability of flexible organic solar cells (OSCs) with minimal impact on device performance. In particular, we compare the addition of styrene-ethylene-butylene-styrene (SEBS) and styrene-ethylene-propylene-styrene (SEPS) co-polymers with varying polystyrene content and molecular weight. Our findings reveal that SEPS exhibits slightly higher miscibility than SEBS. Yet, the miscibility difference is relatively small, and casting conditions that drive local morphology become a larger driver dictating final device performance. In both the SEBS and SEPS additives, we can maintain 95% of the control OSC efficiency. This is achieved while significantly improving the fracture toughness of the OSCs. The fracture energy is shown to be strongly driven by the molecular weight of the additive, and optimized elastomer additives can result in a more than a four-fold increase in OSC fracture toughness.