Perovskite Films Treated with Polyvinyl Pyrrolidone for High-Performance Inverted Perovskite Solar Cells

Energy loss and unstable properties of the interface and grain boundaries (GBs) in perovskite solar cells (PSCs) greatly limit the efficiency and stability of PSCs. Here, a polyvinyl pyrrolidone (PVP) treatment is proposed to overcome these challenges. The impact of PVP treatment on perovskite films and the corresponding performance of the devices are systemically investigated. The crystallinity, GBs, and PbI₂residues of the perovskite films are all improved via the interaction of PVP and perovskite crystals, which results in an increased grain size and enhanced built-in electric field in the devices. The trap density is dramatically decreased from 8.74 × 10¹⁵to 4.37 × 10¹⁵cm^-3, and the additional interface electrical field of 1.26 × 10⁶V/cm is formed at the perovskite/PCBM interface, which dramatically eliminates the energy loss of the bulk and interface of inverted PSCs. Based on this strategy, a high power conversion efficiency (PCE) of 20.77% is achieved based on the MAPbI₃/PCBM planar heterojunction. In addition, the stability of PSCs is also dramatically improved, and the PCE of PVP devices can retain 80% of its initial value after 14 days in air and can retain 99% of its initial value after 64 days in N₂, while the control devices can only retain 44 and 85% of their initial PCE values under the same exposure conditions, respectively.