Matching electron transport layers with a non-halogenated and low synthetic complexity polymer:fullerene blend for efficient outdoor and indoor organic photovoltaics

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 1; no. 19; pp. 1768 - 1779
• Main Authors: Rodríguez-Martínez, Xabier, Riera-Galindo, Sergi, Cong, Jiayan, Österberg, Thomas, Campoy-Quiles, Mariano, Inganäs, Olle
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 17.05.2022; The Royal Society of Chemistry
• Subjects: Acceptor materials; Chemistry; Complexity; Copolymers; Electron transport; Energy conversion efficiency; Energy harvesting; Formulations; Fullerenes; Indoor environments; Interlayers; Laminates; Lamination; Low cost; Photoactivation; Photovoltaic cells; Photovoltaics; Polyethyleneimine; Polymers; Renewable energy; Solar cells; Sustainability; Tin dioxide; Zinc; Zinc oxide
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/d2ta01205g

The desired attributes of organic photovoltaics (OPV) as a low cost and sustainable energy harvesting technology demand the use of non-halogenated solvent processing for the photoactive layer (PAL) materials, preferably of low synthetic complexity (SC) and without compromising the power conversion efficiency (PCE). Despite their record PCEs, most donor-acceptor conjugated copolymers in combination with non-fullerene acceptors are still far from upscaling due to their high cost and SC. Here we present a non-halogenated and low SC ink formulation for the PAL of organic solar cells, comprising PTQ10 and PC 61 BM as donor and acceptor materials, respectively, showing a record PCE of 7.5% in blade coated devices under 1 sun, and 19.9% under indoor LED conditions. We further study the compatibility of the PAL with 5 different electron transport layers (ETLs) in inverted architecture. We identify that commercial ZnO-based formulations together with a methanol-based polyethyleneimine-Zn (PEI-Zn) chelated ETL ink are the most suitable interlayers for outdoor conditions, providing fill factors as high as 74% and excellent thickness tolerance (up to 150 nm for the ETL, and >200 nm for the PAL). In indoor environments, SnO 2 shows superior performance as it does not require UV photoactivation. Semi-transparent devices manufactured entirely in air via lamination show indoor PCEs exceeding 10% while retaining more than 80% of the initial performance after 400 and 350 hours of thermal and light stress, respectively. As a result, PTQ10:PC 61 BM combined with either PEI-Zn or SnO 2 is currently positioned as a promising system for industrialisation of low cost, multipurpose OPV modules. A non-halogenated and low synthetic complexity ink formulation for the photoactive layer of organic solar cells, showing a record PCE of 7.5% in blade coated devices under 1 sun and 19.9% under indoor LED illumination.