A passivation by H2O2-TiO2 interlayer for efficient and stable Carbon-based perovskite solar cells

A major challenge of carbon-based perovskite solar cells (C-PSCs) is boosting photovoltaic performance and stability. However, their performance can be limited by undesirable increases in trap states densities and nonradiative recombination caused by defects at the interface between the perovskite and the electron transporting layer (ETL) and in the bulk perovskite. Herein, a novel passivation using H2O2-TiO2 interlayer provides an effective approach to improve the interfacial bridging between TiO2 and perovskite in C-PSCs. Additionally, the surface morphology of the HT interlayer was elaborated by varying spin coating speeds of deposition. A suitable spin coating speed was found to be 3000 rpm, called TiO2/HT-3000 ETL. This allows lower oxygen vacancy within an interfacial layer and promotes high-quality growth of perovskite film with fewer grain boundaries. TiO2/HT-3000 ETL-based C-PSCs in a homemade air-filled dry glove box achieved a PCE of 16.23%, which improved the open-circuit voltage and fill factor values. These results can be attributed to effectively reduced trap state densities and nonradiative recombination losses in the device. In addition, the newly constructed TiO2/ HT-3000 ETL can notably enhance the long-term stability in ambient air without encapsulation. This simple interface passivation strategy proposes a new path toward the commercialization of perovskite solar cells.