Regulation of the low-temperature processed TiO2 buried interface to enhance the efficiency of CsPbI2Br-based all-inorganic perovskite solar cells

All-inorganic CsPbI x Br 3-x perovskite solar cells (PSCs) exhibit excellent thermal stability and high efficiency, but their power conversion efficiency (PCE) remains lower than that of organic–inorganic hybrid PSCs. This is primarily due to the significant open-circuit voltage (V oc ) loss at the buried interface of electron transport layer (ETL) and perovskite film. Moreover, low-temperature processed TiO 2 ETL simultaneously suffers from more trap-states which will deteriorate the PCE and stability of PSCs. To solve these issues, zinc acetate (Zn(OAc) 2 ) is employed to optimize the TiO 2 /CsPbI 2 Br buried interface to reduce the V oc loss and improve the PCE and device stability. This Zn(OAc) 2 interfacial modification0020increases the V oc about 90 m V from 1.159 V to 1.248 V. Consequently, Zn(OAc) 2 -modified CsPbI 2 Br PSCs (Target I-PSCs) achieve a champion PCE of 14.91 % with a fill factor over than 80 %, which is significantly higher than the 12.25 % of reference I-PSCs. A series characterizations confirm that the improved performance is attributed to the increased electrical conductivity of the modified TiO 2 film, the passivated defects on the TiO 2 surface and the uncoordinated Cs + /Pb 2+ traps at the bottom of CsPbI 2 Br film, as well as the optimized the energy level alignment to facilitate electron transport and collection. This work provides a feasible strategy to fabricate efficient and stable CsPbI 2 Br I-PSCs by modifying the TiO 2 /CsPbI 2 Br buried interface by Zn(OAc) 2 .