This PDF file contains the front matter associated with SPIE Proceedings Volume 11496, including the Title Page, Copyright Information, and Table of Contents.

Welcome to the conference on New Concepts in Solar and Thermal Radiation Conversion III. Here, we aim to explore a range of concepts and experiments relating to the effective conversion of radiation into alternative forms of energy and power. These include sessions on high-efficiency thermophotovoltaics, selective thermal transport, solar photovoltaics, reliability aspects of photovoltaics, artificial photosynthesis, solar fuels, and the stability of perovskite solar cells. A range of video and poster presentations will be available in this virtual forum, and participants are encouraged to follow-up with individual presenters with any specific questions or comments.

Thermophotovoltaic (TPV) cells utilize locally emitted thermal radiation to generate electricity. To reach high efficiencies, the unusable spectrum (the below bandgap, or out-of-band spectrum) of the thermal source must be recycled to the source. Current approaches for photon recycling use back-surface reflectors or front surface filters, however, these have not exceeded 95 % out-of-band reflectance. In this work, we demonstrate an out-of-band reflectance of ~99% in a thin-film In0.53Ga0.47As TPV using an air-bridge as photon reflector, which effectively eliminates out-of-band absorption losses. The nearly perfect photon utilization enables a record high TPV power conversion efficiency of over 31% measured with a 1500K blackbody emitter.

Solar thermal absorbers experience heat losses at high temperatures, thus limiting their efficiencies. In this work we present an InfraRed (IR) window coating capable of recycling thermal radiation back to the absorber to reduce losses and improve efficiencies. This mechanism is what we call cold-side external photon recycling. Several designs have been investigated in a preliminary study, ranging from a simple alternation of two different optical materials, as in the case of a Distributed Bragg Reflector (DBR) design, to more complex structures like the rugate filters. The ideal design of a rugate filter makes use of a huge number of different optical materials and layers, useful to reach a continuous variation of the refractive index profile which guarantee a minimization of the undesired reflections. Here, we show that some of these advantages can still be obtained by using a limited number of materials coupled with a proper design, and we extend prior theoretical work to include a realistic set of materials for ease of fabrication and validation. The resulting IR mirror, based on a rugate-multilayer structure, presents favorable properties: the high transmissivity in the visible region of the spectrum allows the Solar radiation to reach the absorber, without altering its performance greatly; instead, a reflection window width of almost 1 µm in the mid-IR region allows for partial recovery of heat radiated by the absorber that otherwise would be lost, and the reduced number of materials can simplify fabrication. Finally, the design has been developed for the particular case of a high-vacuum flat solar thermal panel, but it could be applied to any solar thermal device with an emissive surface without altering the absorber performance greatly.

Cleaner power generation technologies are needed to reduce our reliance on fossil fuels and to reduce the negative effects of climate change, but will that be enough? In this talk, I will discuss our latest work on two fronts. First, I will discuss how to make more efficient photovoltaic devices and sensors through the extraction of thermally energetic carriers (e.g. hot carriers) before they relax. Second, I will discuss the potential of radiative cooling to modify the global energy flux to combat global warming.

Strong coupling between light and ionic vibrations in matter (phonons) gives rise to composite light-matter waves referred to as phonon polaritons (PhPs). Such strong coupling is common in polar semiconductors within a spectral band in the infrared (IR) known as the reststrahlen band. While bulk materials are essentially near-perfect reflectors in the reststrahlen band, structured materials have vast capabilities in their photonic responses. We leverage here the permittivity responses induced by phonon polaritons to design structures behaving as near-perfect absorbers/thermal emitters. We discuss a lithography-free design route to near-perfect absorption within a material layer as thin as one thousandth the free space wavelength. Furthermore, we present a paradigm inspired by moth eyes exhibiting all-angle near-unidirectional absorption and thermal emission. Our findings are relevant to the development of selective thermal emitters and passive radiative cooling devices.

Thermal management is extremely important for renewable energy systems such as photovoltaics (PV), thermophotovoltaics (TPV) and concentrating photovoltaics (CPV). Elevated operating temperatures not only reduce the efficiency of PV modules, but also substantially reduce their lifetimes. This is an even more critical issue for higher heat load systems, such as TPV and CPV, where low-bandgap solar cells are commonly used, making the system more sensitive to temperature increases. Radiative cooling can reject significantly more waste heat than convection and conduction at high temperatures by sending it directly into space. Therefore, in this study, we examine an outdoor radiative cooling system that consumes no power while realizing a substantial reduction in operating temperature, which may be suitable for substantially improving the performance and lifetime concentrating photovoltaics.

Improved photovoltaic efficiencies by incorporating an internal front reflector in addition to an ideal back reflector is limited to devices with absorber bandgaps below ~1.34 eV due to the availability of AM1.5G photons above the reflector energy-cutoff, i.e. reflector bandgap. However, energy-selective front reflectors especially benefit photovoltaic devices under monochromatic illumination, i.e. laser power converters (LPCs). The efficiency improvements with and without a front reflector as a function of solar cell bandgap are compared under AM1.5G versus monochromatic light at the reflector bandgap. For a GaAs solar cell, where front reflectance enhancements are negligible, over 5% absolute efficiency increase is predicted in a GaAs LPC with a front reflector (605 nm illumination). Bandgap reduction further increases the efficiency enhancement under monochromatic illumination, where up to 60% relative efficiency increase can be achieved at Eg =0.5 eV with E_laser = 1.467 eV.

The integration of energy-harvesting and storage in a single device is considered to be one of the most demanding technologies for future wireless sensors. Photovoltaic supercapacitors are among promising solutions with the dual properties of photoelectric and electrochemical charge storage. In order to improve the efficiency in hybrid photovoltaic supercapacitors, most research has focused on studying electrode materials. In this work, we have studied the effect of polyaniline (PANI) concentration in a composite gel-based electrolyte on the impedance of the device. The photovoltaic supercapacitors were fabricated in a two-electrode configuration combining a titanium dioxide (TiO₂) coated on fluorine-doped tin oxide (FTO) glass as the working electrode, a multi-walled carbon nanotube (MWCNT) porous electrode as the counter electrode, and a composite gel-based electrolyte. The composite gel was made of polyvinyl alcohol (PVA), hydrochloric acid (HCl), ammonium persulfate (APS), and different concentrations of aniline (ANI). The impedance study of the gel with 0.5 mM concentration of PANI showed a two-stage charge storage mechanism associated to the double-layer at the electrode-electrolyte interface and a pseudo-capacitive charge storage mechanism in the bulk of the electrolyte. The absorption spectrum of the synthesized gel shows a strong absorption peak near 780 nm confirming the formation of the emeraldine salt of PANI in the gel. The current results are inspiring the research for optimizing the composite material to improve both energy harvesting and the charge storage stability in photovoltaic supercapacitors.

Dye sensitized solar cells (DSSCs) are electrochemical solar cells depending on dye molecules that absorbing the radiation and start generating the photoelectrons. DSSCs are the most harmonious device among the other types of solar cells to be coupled with the energy storage devices such as pseudocapacitors to make a solar-capacitor device because of their electrochemical nature. Pseudocapacitors are electrochemical devices that can store charges through the double layer structure and changing the oxidation state of conducting polymer materials (i.e. Polypyrrole, Ppy). The effect of adding methylene blue dye molecules (MB) to the solar capacitor device was absorbed in the previous work by recording the voltage of the composite materials Ppy+MB under the effect of illumination by 23 ∆mV. In this work, TiO₂ as electron transport layer (ETL) was added to the anode electrode to facilitate the movement of photo generated electrons. The results of solar-capacitor device exhibited 570 ∆mV open circuit voltage under the effect of light condition in 400 s. The short circuit current results showed a 2 uA under the light condition. The presented results are hopeful to enhance the performance of solar energy and charge storage devices.

Carrier multiplication (CM) is the amplification of the excited carrier density by two times of more when the incident photon has larger energy than two times band gap of semiconductors. Previously, most of studies in CM have been carried out with optical and device approaches. So, we suggest a unique approach to investigate the carrier multiplication via photocurrent measurement using the PbS quantum dot (QD)-decorated AFM tip in conductive atomic force microscope (CAFM). The quantum yield (QY) evaluated from photocurrent results represents a step-like behavior, and the carrier multiplication (CM) threshold energy is as low as twice the band gap owing to efficiently extracting photogenerated carriers with the short channel and the role of graphene for a counter electrode. This CAFM-based photocurrent technique suggests a simple and straightforward method to evaluate the CM phenomena in low dimensional materials.

The excessive utilisation of conventional energy sources has highlighted a complicated energy crisis due to high dependency and depletion of non-renewable resources; along with the inefficiency to cope up with the pressing requirements of the economy. Shifting to alternative, replenishable forms of energy and developing technology for the same, will fulfil the current energy needs and complement the national security. Solar energy can be productively exercised to meet the current energy requirements. Shading analysis is one of the most critical steps essential to any successful installation of a solar energy system. In photovoltaics, it is important to analyze shading caused by surrounding objects and/or vegetation. In special cases like analysis or design of BIPV systems, the exact analysis of shadow-voltaic systems (overhangs, vertical shading fins, awnings, etc.) is also very important. Detection of shading is important in photovoltaics installations and shall be eliminated or minimized as much as possible. Even small obstacles in any colonial set-up like chimneys, telephone poles, etc. shouldn't be neglected. To minimize the influence of photovoltaic array shading (if shading cannot be avoided), we hereby present first of its own kind smartphone application backed with Deep learning algorithms, designed to calculate effective solar insolation, perform shading analysis, check the efficacy of the site and list the related requirements for the installation of photovoltaic systems.

This work focused on the technology of luminescent down shift (LDS), with a primary aim to identify and investigate a methodology to introduce the metallic oxides as inorganic luminescent materials into EVA and PVB polymer encapsulant as emergent materials for photovoltaic application. For this goal, we propose to study the feasibility to implement the LDS functionality and to identify suitability of available luminescent to be incorporated into the host polymer encapsulant material. The first step to this direction was through a comprehensive optical study of metallic oxides nanoparticles in organic solvent. The methodology and experimental conditions such as laboratory polymer preparation and luminescence dye concentration were presented. Also, the emergent polymer encapsulant sheets were characterized by using optical analysis techniques. The absorption spectrum of the prepared PVB material shifts towards longer wavelengths, with increasing metallic oxides concentration.

In this paper, we propose to study the quality analysis of emerging EVA, comparatively to other encapsulant materials, in the PV market by additional analysis contribution developed in our recent investigations by using optical techniques (UV-visible transmission, photoluminescence…) and thermal analysis techniques. This contribution can induce a new methodology for long term PV module reliability in situ and outdoor exposure by using emerging encapsulant materials.

Local build-up of pH gradients is a major concern in near-neutral photoelectrochemical water splitting since it leads to efficiency losses due to concentration overpotentials. Here, we monitor in-situ pH changes during water splitting in a (photo)electrochemical cell by a fluorescence-based technique and compared with multi-physics simulations. We found that the pH distribution within the cell is affected by natural convection generated by the electrochemical reactions. Based on this observation, we developed a model that considers natural convection driven by buoyancy forces due to local changes in the density of the electrolyte. Only when the buoyancy effect is considered does the model accurately reproduces the measured pH profile. This study reveals the importance of natural convection driven by electrochemical reactions and highlights the implications for designing efficient photoelectrochemical devices.

Recent study demonstrated that the performance of α-SnWO₄/NiO_x photoabsorbers prepared by pulsed laser deposition (PLD) is limited by the interfacial properties; ^[1] understanding this interface is therefore crucial for further improvement. A thorough α-SnWO₄/NiO_x interface investigation by means of hard X-ray photoelectron spectroscopy (HAXPES) is presented and correlated with photoelectrochemistry measurements. PLD NiO_x introduces strong upwards band bending (~500 meV) at the interface. However, photoemission spectra simulation indicates that at the same time a thin SnO₂ layer is formed at the interface. The implications of this SnO₂ layer to the interface junction properties and the limited photovoltage will be discussed. ^[1] Kölbach et al. Chem Mater. 30 (2018) 8322-8331

Extending some new ideas on the topic of thermoelectric generator modules (TEGs), this paper analysis theoretically and mathematically the efficiency of thermoelectric modules when there is a specific cryogenic temperature on cold side i.e. exactly when the cold side temperature is -157°C, which is the temperature of shadow side of space stations (satellites and approximately surface temperature of moon and mars planets during nights) and there is 121°C on hot side of TEG module that is the temperature on sun-facing side of space stations (satellites and approximately surface temperature of moon and mars planets during days), and it also follows some independent new ideas to increase efficiency of TEG modules in all conditions, that is implementation of periodic structure of terahertz piezoelectric materials as chirped tilted superlattice for the phonon reflection to decrease thermal conductance significantly and benefit from piezoelectric characteristic of zinc oxide to harvest some fraction of wasted thermal energy as well.

Solar simulators are built using various types of light sources having a spectrum similar to that of the sun. Some of these light sources include but are not limited to Xenon Arc Lamps, Metal Halide Arc Lamps and Quartz Tungsten Halogen Lamps. Since these lamps showed several disadvantages related to high cost, light stability, temporal stability and complexity, the usage of high-power LEDs was proposed as a simple and low-cost alternative. This solution boosted the popularity of solar simulators in the field of optical characterization. An array of LEDs is used to create a light source based on mixing different LED's colors with different spectrums, to produce a spectrum similar to that of the sun with a very low mismatch factor. In this paper we will introduce our implemented design with which we managed to reach a 12% mismatching factor at a distance 10 cm from the light source.

System sizing is necessary for evaluating the PV system as first step before investing at a given project. However, there is a lack of developing MATLAB code for grid-connected system to present a techno-economic solution taking into consideration the less running time and covering our local needs. This paper aims to develop a pre-sizing offline tool using MATLAB software. Moreover, the developed code is integrated with tariffs and electricity bills for both low and medium voltages including all sectors. Furthermore, the tool is applied for all applicable areas like rooftop industrial shed and ground mounted. Hence, Egypt was applied in this tool through selecting four locations Cairo, Alexandria, Aswan and Hurghada. Case studies were sized using MATLAB code and validated by PVsyst, as result the percentage of error ranges from 1 to 6%. Additionally, developed code shows the capability of giving a full techno-economic solution in preliminary design stage. The results showed that Aswan was the best location for installing PV system technically and economically where the highest specific yield and capacity factor recorded were 2062 kWh/kWp/year, 24% respectively. Moreover, the lowest levelized cost of energy and simple payback period 0.56 EGP/kWh, 4.3 years respectively were recorder in Aswan.