Anode Buffer Layer Selection for Efficient Flexible Perovskite Indoor Photovoltaics

Flexible carbon-electrode perovskite solar cells (PSCs) could be one of the applicable photovoltaic technologies for weak-light application that is featured with low cost, fast renewability, and facile device integration. The performance of this photovoltaic lags behind that of PSCs with metal electrodes, which is primarily ascribed to the lack of an efficient buffer layer/carbon combination. Here, in this work, we systematically researched two typical anode structures, including polythiophene/nickel oxide (P3HT/NiOx) and 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (Spiro-OMeTAD) as hole-transporting layers (HTLs) and blade-coated carbon (B-C) or a pressed self-standing carbon film (P-C) as the anode. Comprehensive characterizations reveal that pressing carbon on the P3HT/NiOx HTL resulted in weak physical and electrical contacts, while blade-coated carbon on Spiro caused damage to the electrical properties of the organic HTL during the required annealing of the carbon film. However, the P3HT/NiOx/B-C and Spiro-OMeTAD/P-C anode structures enabled remarkable photovoltaic performance under indoor weak light, with the champion efficiencies reaching 40.5 and 42.5%, respectively, for these two flexible PSCs. Through the systematic design and comparison of anode buffer layers, our work offers referential choice on the device structure for efficient flexible carbon-electrode PSCs that are promising for indoor photovoltaic application.