Light harvesting and carrier transfer enhancement of all-inorganic CsPbBr3 perovskite solar cells by Al-doped ZnO nanorod arrays

Zinc oxide nanorod arrays (ZnO NRAs) have been previously introduced as electron transport layer (ETL) of perovskite solar cells (PSCs) due to their high electron mobility and unique textured morphology. However, the presence of hydroxyl and oxygen vacancies on the surface of bare intrinsic ZnO NRAs may act as defect centers leading to carrier nonradiative recombination and the device photovoltaic performance degradation. Here, we propose a mutilayer SnO2/Al-doped ZnO nanorod arrays/SnO2 (SnO2/AZO NRAs/SnO2) composite to be utilized as ETL of all-inorganic CsPbBr3 PSCs. The influence of AZO NRAs with various Al ion (Al3+) doping content on the performance of CsPbBr3 PSCs was explored. The hole-free carbon-based CsPbBr3 PSCs with an architecture of FTO/SnO2/AZO NRAs/SnO2/CsPbBr3/carbon based on 1 at% AZO NRAs exhibited the best photovoltaic performance with a champion power conversion efficiency (PCE) of 7.11 %, open-circuit voltage (Voc) of 1.46 V, short-circuit current density (Jsc) of 6.88 mA/cm2, and fill factor (FF) of 71.1 %, compared with the bare intrinsic ZnO-based counterpart with a PCE of 3.45 %, Voc of 0.80 V, Jsc of 8.46 mA/cm2, and FF of 51 %, respectively. The photovoltaic performance enhancement can be atrributed to enhanced light collection and electron extraction capability, with lower open-circuit voltage loss and more suitable interface band alighment. It is notable that the AZO NRAs were prepared by a facile electrodeposition approach to obtain large-area textured ETLs. This strategy may also be applicable to the photovoltaic performance improvemet of all types of PSCs.