Photostable electron-transport-layer-free flexible graphene quantum dots/perovskite solar cells by employing bathocuproine interlayer

Electron transport layer (ETL)-free perovskite solar cells (PSCs) are very useful for the low-temperature process that can reduce the instability caused by the ETL such as TiO2 layer. There are several publications on ETL-free PSCs, but most of them are based on transparent conductive oxides, not suitable for flexible applications. Here, we first report photostable ETL-free PSCs of maximum 15.72% power conversion efficiency (PCE) by employing an insulating interlayer of bathocuproine (BCP) between the graphene (GR) transparent conductive electrode (TCE) and the graphene quantum dots-added perovskite layer. The BCP interlayer effectively enhances the electron carrier injection by reducing the recombination centers at the active layer/GR TCE interface. Only 8 or 17% of the original PCE is lost under ambient conditions or under light soaking, respectively for 500 h. A flexible-type of the PSC shows a PCE comparable to that of the rigidtype counterpart, and 83% of the initial PCE is maintained even after 1000 repeated bending tests at a radius of 4 mm. These results suggest that the ETL-free PSCs exhibit excellent long-term and mechanical stabilities. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Perovskite solar cells without an electron transport layer show promising power conversion efficiency with improved stability, utilizing an insulating interlayer of bathocuproine. The inclusion of graphene quantum dots enhances electron carrier injection, leading to photostable performance and mechanical robustness suitable for flexible applications.