Improving Thermal and Photostability of Polymer Solar Cells by Robust Interface Engineering

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2022-06, Vol.18 (23), p.e2107834-n/a
• Main Authors: Su, Li‐Yun, Huang, Hsin‐Hsiang, Tsai, Chang‐En, Hou, Cheng‐Hung, Shyue, Jing‐Jong, Lu, Chien‐Hao, Pao, Chun‐Wei, Yu, Ming‐Hsuan, Wang, Leeyih, Chueh, Chu‐Chen
• Format: Article
• Language: English
• Subjects: bulk‐heterojunction morphology; Charge transfer; Control equipment; Dipoles; Electron transport; Energy conversion efficiency; Glove boxes; Graphene; graphene oxide nanosheets; Heterojunctions; Interface stability; Morphology; Nanotechnology; photostability; Photovoltaic cells; polymer solar cells; Pyrolysis; Robustness; Solar cells; thermal stability; Zinc oxide
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202107834

As the power conversion efficiency (PCE) of organic photovoltaics (OPVs) approaches 19%, increasing research attention is being paid to enhancing the device's long‐term stability. In this study, a robust interface engineering of graphene oxide nanosheets (GNS) is expounded on improving the thermal and photostability of non‐fullerene bulk‐heterojunction (NFA BHJ) OPVs to a practical level. Three distinct GNSs (GNS, N‐doped GNS (N‐GNS), and N,S‐doped GNS (NS‐GNS)) synthesized through a pyrolysis method are applied as the ZnO modifier in inverted OPVs. The results reveal that the GNS modification introduces passivation and dipole effects to enable better energy‐level alignment and to facilitate charge transfer across the ZnO/BHJ interface. Besides, it optimizes the BHJ morphology of the photoactive layer, and the N,S doping of GNS further enhances the interaction with the photoactive components to enable a more idea BHJ morphology. Consequently, the NS‐GNS device delivers enhanced performance from 14.5% (control device) to 16.5%. Moreover, the thermally/chemically stable GNS is shown to stabilize the morphology of the ZnO electron transport layer (ETL) and to endow the BHJ morphology of the photoactive layer grown atop with a more stable thermodynamic property. This largely reduces the microstructure changes and the associated charge recombination in the BHJ layer under constant thermal/light stresses. Finally, the NS‐GNS device is demonstrated to exhibit an impressive T80 lifetime (time at which PCE of the device decays to 80% of the initial PCE) of 2712 h under a constant thermal condition at 65 °C in a glovebox and an outstanding photostability with a T80 lifetime of 2000 h under constant AM1.5G 1‐sun illumination in an N2‐controlled environment. Functionalized graphene oxide nanosheets (GNSs) are synthesized to modify the inorganic ZnO electron transport layer (ETL) in inverted organic photovoltaic devices (OPVs). The GNS‐modification enables better energy‐level alignment and facilitates charge transfer across the ZnO/BHJ interface. Moreover, it stabilizes the morphology of the ZnO ETL and enhances the thermodynamic nature of the photoactive layer. These combined advantages largely reduce the microstructure changes and the charge recombination in the BHJ layer under constant thermal/light stresses.