Semi-transparent Organic Solar Cells for Greenhouse Application
Yuan Xiong1*, Eshwar Ravishankar2, Jennifer Swift3, Harald Ade1*, Ronald Booth2, Melodi Charles4, Reece Henry1, Brendan O’Connor2, Jeromy James Rech5, Carole Saravitz3, Heike Sederoff4, Long Ye1, Wei You5
1. Department of Physics, Organic and Carbon Electronics Lab (ORaCEL), North Carolina State University, Raleigh, NC 27695, USA
2. Department of Mechanical and Aerospace Engineering and ORaCEL, North Carolina State University, Raleigh, NC 27695, USA
3. Department of Plant Biology, North Carolina State University, Raleigh, NC 27695, USA
4. Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
5. Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
E-mail: firstname.lastname@example.org; email@example.com
Semitransparent organic solar cells (ST-OSCs) show great potential in building-integrated photovoltaics due to the advantages in solution processability, flexibility, and transparency. Herein, we present a systematic study on the application of high-performance ST-OSC filters in a greenhouse by utilizing three representative systems with different spectral responses, namely, FTAZ:PC71BM, FTAZ:IT-M[2, 3], and PTB7-Th:IEICO-4F. Specifically, the cultivation of red leaf lettuce is conducted in a controlled environment growth chamber, which is possible to duplicate any climate, and under different ST-OSC filters. In principle, the ST-OSCs absorb a portion of the solar spectrum for power generation and lettuce utilizes the penetrated light for photosynthesis. Furthermore, we quantitatively investigate the leaf area and number profiles, plant biomass, and photosynthetic rate under the as-prepared ST-OSC filters treatments. On the base of statistical analysis after the growth cycle, we can identify the best ST-OSC for plant growth. These results thus pave the way to integrate ST-OSCs with greenhouses.
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Casting of a donor:acceptor bulk-heterojunction structure from a single ink has been the predominant fabrication method of solution-processed organic photovoltaics (OPVs). Despite the success of such bulk-heterojunction, the task of controlling its microstructure in a single casting process has been challenging and arduous and alternative approaches are desired. To achieve and even improve OPVs with a desirable microstructure, a facile and eco-compatible sequential deposition approach is demonstrated for nonfullerene polymer/small molecule pairs. Using a known weakly crystalline polymer FTAZ as the model material, we show the profound influence of casting solvent on the molecular ordering of the film, and thus the device performance and mesoscale morphology of sequentially deposited OPVs can be tuned. Static and in-situ X-ray scattering indicate that applying the green solvent limonene is able to greatly promote the molecular order of FTAZ and form the largest domain spacing exclusively, which correlate well with the best efficiency in sequentially deposited devices. The sequentially cast device generally outperforms its control device based on traditional single-ink bulk-heterojunction structure. Investigations of distinct material systems suggest that our approach be applicable to many conjugated polymers and nonfullerene acceptors, which yield consistently higher fill factors than traditional bulk-heterojunction devices. Moreover, the relationships between polymer:solvent interactions, thin-film microstructure, and device performance are discussed for these sequentially deposited devices. It is noted that polymer:solvent interaction parameter χ positively correlates with domain spacing in the devices. Our findings shed light on innovative approaches to rationally create ink-stable, environmentally friendly, and highly efficient nonfullerene solar cells.
 Ye, L.; Xiong, Y.; Chen, Z.; Zhang, Q.; Fei, Z.; Henry, R.; Heeney, M.; O’Connor, B.; You, W.; Ade, H. Adv. Mater. 2019, under review.
 Ye, L.; Xiong, Y.; Zhang, Q.; Li, S.; Wang, C.; Jiang, Z.; Hou, J.; You, W.; Ade, H. Adv. Mater. 2018, DOI: 10.1002/adma.201705485.