Improvement of the performance of carbon based all-inorganic perovskite solar cells by using ammonium acetate modified rutile TiO2 nanorods array as the electron transport layer

Carbon-based all-inorganic perovskite solar cells are currently emerging as a commercial and promising photovoltaic device. Rutile TiO2 has the function of UV shielding and preventing the decomposition of perov-skite, furthermore, TiO2 nanorod array provides the direct 1-D electron transmission channel. Herein, vertically oriented rutile TiO2 nanorods array are synthesized on the FTO substrate by a simple one-step hydrothermal process and used as the electron transfer layer. The analysis of characterization illustrates that the prepared TiO2 is a flawless single rutile phase. TiO2 nanorods are employed as an ETL to provide a passage for the rapid and direct charge transfer. The separation of electrons and holes can be enhanced by ammonium acetate treatment of the TiO2 nanorod ETL/perovskite interface, and the carrier recombination can be efficiently lowered. Based on the structure of FTO/TiO2@CH3COONH4/CsPbI2.25Br0.75/C, the best device containing 2.5 mg/mL ammonium acetate modified TiO2 nanorods showed a short-circuit current density of 14.55 mA/cm2, open-circuit voltage of 1.08 V, and fill factor of 69.45 %, yielding a power conversion efficiency of 11.53 %, which show an increase in efficiency of approximately 22.4% when compared with the control cell. The results show that ammonium ac-etate interface modification is an effective strategy to enhance the photovoltaic performance of PSCs.