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The integration of semi-transparent organic solar cells (ST-OSCs) in greenhouses offers new agrivoltaic opportunities to meet the growing demands for sustainable food production. The tailored absorption/transmission spectra of ST-OSCs impacts the power generated as well as crop growth, development and responses to the biotic and abiotic environments. We grew lettuce and tomato, traditional greenhouse crops, under three ST-OSC filters that create different light spectra. Lettuce yield and early tomato development are not negatively affected by the modified light environment. Our genomic analysis reveals that lettuce production exhibits beneficial traits involving nutrient content and nitrogen utilization while select ST-OSCs impact regulation of flowering initiation in tomato. ST-OSCs integrated into greenhouses are not only a promising technology for energy-neutral, sustainable and climate-change protected crop production, but can deliver benefits beyond energy considerations.

International audience; Bulk heterojunction polymer solar cells based on a novel combination of materials are fabricated using industry-compliant conditions for large area manufacturing. The relatively low-cost polymer PTQ10 is paired with the non-fullerene acceptor 4TIC-4F. Devices are processed using a non-halogenated solvent to comply with industrial usage in absence of any thermal treatment to minimize the energy footprint of the fabrication. No solvent additive is used. Adding the well-known and low-cost fullerene derivative PC61BM acceptor to this binary blend to form a ternary blend, the power conversion efficiency (PCE) was improved from 8.4% to 9.9% due to increased fill factor (FF) and open circuit voltage (VOC), while simultaneously improving the stability. The introduction of PC61BM is able to balance the hole-electron mobility in the ternary blends, which is favourable for high FF. This charge transport behavior is correlated with the bulk heterojunction (BHJ) morphology deduced from Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS), Atomic Force Microscopy (AFM) and surface energy analysis. In addition, the industrial figure of merit (i-FOM) of this ternary blend was found to increase drastically upon addition of PC61BM due to an increased performancestability-cost balance.

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: yxiong8@ncsu.edu; hwade@ncsu.edu 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[1], FTAZ:IT-M[2, 3], and PTB7-Th:IEICO-4F[4]. 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. [1] S. C. Price, A. C. Stuart, L. Yang, H. Zhou, W. You, Journal of the American Chemical Society 2011, 133, 4625. [2] L. Ye, Y. Xiong, Q. Zhang, S. Li, C. Wang, Z. Jiang, J. Hou, W. You, H. Ade, Advanced Materials 2018, 30, 1705485. [3] Y. Xiong, L. Ye, A. Gadisa, Q. Zhang, J. J. Rech, W. You, H. Ade, Advanced Functional Materials 2019, 29, 1806262. [4] X. Song, N. Gasparini, L. Ye, H. Yao, J. Hou, H. Ade, D. Baran, ACS Energy Letters 2018, 3, 669.

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[1]. 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[2] 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. Reference [1] 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. [2] 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.

Organic solar cells that have all-polymer active layers may have several advantages compared with polymer-small molecule systems including improved mechanical and thermodynamic stability; however, an all-polymer active layer does not guarantee robust mechanical behavior. Here, we consider key parameters that may influence the mechanical behavior and power conversion efficiency of all-polymer solar cells (all-PSCs). Considerations include the thermal transition temperature of the polymers, the molecular weight (MW) of the polymers, and film morphology. The impact these features have on mechanical behavior is probed by measuring the cohesive fracture energy (Gc), crack onset strain, and elastic modulus. We find that the selection of ductile polymers with high MW enhances interchain interactions that improve the mechanical resilience of the films. High-MW polymers are also found to maximize the power conversion efficiency (PCE). Using this strategy, BHJ films with the best reported combination of Gc (7.96 J m-2) and PCE (6.94%) are demonstrated. Finally, it is found that increasing the film thickness increases the fracture energy of the films but at the cost of PCE. These findings provide a fundamental perspective on the design strategy to achieve high performance and mechanically robust organic solar cells.

Summary Adding semitransparent organic solar cells (ST-OSCs) to a greenhouse structure enables simultaneous plant cultivation and electricity generation, thereby reducing the greenhouse energy demand. However, there is a need to establish the impact of such systems on plant growth and indoor climate and to optimize system tradeoffs. In this work, we consider plant growth under OSCs and system-relevant design. We evaluate the growth of red leaf lettuce under ST-OSC filters and compare the impact of three different OSC active layers that have unique transmittance. We find no significant differences in the fresh weight and chlorophyll content of the lettuce grown under these OSC filters. In addition, OSCs provide an opportunity for further light and thermal management of the greenhouse through device design and optical coatings. The OSCs can thus affect plant growth, power generation, and thermal load of the greenhouse, and this design trade space is reviewed and exemplified.

Organically modified chalcogenide (ORMOCHALC) polymers have proven to be alternatives to the conventional inorganic materials for mid-wavelength infrared (MWIR, λ = 3–5 μm) optical components. While the refractive index of ORMOCHALC can be reinforced by the content of chalcogenides such as sulfur (S) and selenium (Se), the increased portion of the S or Se deteriorate the thermomechanical stabilities. As a remedy, this study utilizes ZnS nanoparticles to reinforce both optical and thermomechanical properties of the sulfur-based ORMOCHALC polymer, poly(S-random-1,3-diisopropenylbenzene). The refractive index n and extinction coefficient k of the nanocomposites were characterized by Infrared Variable Angle Spectroscopic Ellipsometry (IR-VASE). The results show a significant increment in the refractive index of Δn = 6.58% at the wavelength of 4 μm by adding 20 wt% ZnS (or 7.29 vol%) in the ORMOCHALC polymer. The low extinction coefficient of the nanocomposites (

Casting of a donor:acceptor bulk-heterojunction structure from a single ink has been the predominant fabrication method of organic photovoltaics (OPVs). Despite the success of such bulk heterojunctions, the task ofcontrolling the microstructure in a single casting process has been arduous and alternative approaches are desired. To achieve OPVs with a desirable microstructure, a facile and eco-compatible sequential deposition approach is demonstrated for polymer/small-molecule pairs. Using a nominally amorphous polymer as the model material, the profound influence of casting solvent is shown 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 (R)-(+)-limonene is able to greatly promote the molecular order of weakly crystalline polymers and form the largest domain spacing exclusively, which correlates well with the best efficiency of 12.5% in sequentially deposited devices. The sequentially cast device generally outperforms its control device based on traditional single-ink bulk-heterojunction structure. More crucially, a simple polymer:solvent interaction parameter χ is positively correlated with domain spacing in these sequentially deposited devices. These findings shed light on innovative approaches to rationally create environmentally friendly and highly efficient electronics.