Reduced Graphene Oxide/Bi2O3 Composite as a Desirable Candidate to Modify the Electron Transport Layer of Mesoscopic Perovskite Solar Cells

Perovskite (PVK) materials as a promising candidate for next-generation photovoltaic devices have been widely developed by scientists to solve global warming concerns. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been raised up to 25%, a competitive value with silicon-based solar cells. Low shelf stability is one of the first concerns of PSCs and should be considered by researchers' attempts. In this regard, many attempts have been reported for designing graphene-based composite nanoparticles (NPs) for use in the PSCs. Here, to boost the PCE and shelf stability of triple cation PSCs, the electron transport layer (ETL) was modified with novel reduced graphene oxide (rGO) combined with bismuth oxide (Bi2O3), which was prepared with a simple mixing of rGO and Bi2O3. Different volume ratios of rGO/Bi2O3 were added to the mp-TiO2 precursor and used as a modified ETL in the PSCs. It was found that rGO/Bi2O3 composite improves the conductivity of the ETL and boosts the electron extraction to the FTO electrode. Besides this, the rGO/Bi2O3 composite improved the ETL/PVK interface and consequently reduced charge recombination in this interface. The PCE of the PSCs reached 17.21% after the ETL modification process compared with 13.41% for unmodified PSCs. Finally, a more stable behavior in modified PSCs was observed, which shows that the resistance of the modified PVK layer to composition degradation is higher than that of unmodified layers.