Study of performance and stability of hole transport layer-free perovskite solar cells with modified electron transport layer

The electron transport layer (ETL) performs a functional role in the structure of perovskite solar cells (PSCs). Here in this study, various additives were used to improve the electron transport layer and the performance of PSCs. Recently, carbon nanostructures have shown the capability to be a good candidate to improve the performance of perovskite solar cells. In this study, carbon nanostructures of reduced graphene oxide (RGO), carbon quantum dots (CQDs), and a combination of these, were used in the mesoporous TiO₂ precursor solution (mTiO₂) to increase the performance and stability of hole-transport-free PSCs. The use of these materials due to their unique properties in the electron transfer layer has facilitated, increased electron transfer, and improved the surface of the perovskite layer. These factors have increased the efficiency and performance of PSCs. Using these materials, the power conversion efficiency (PCE) of PSCs was increased from 5.88% without additives to 10.92% with additives and improved the stability than the pristine sample. The best-optimized PCE and stability are related to adding a combination of CQDs and RGO with a ratio of 50:50 into the electron transport layer, the device structure is Fluorine-doped tin oxide (FTO)/cTiO₂/ CQDs+RGO+mTiO₂/methylammonium lead iodide (MAPbI₃)Au.