High Efficiency MAPbI 3 Perovskite Solar Cell Using a Pure Thin Film of Polyoxometalate as Scaffold Layer

Here, we successfully used a pure layer of [SiW 11 O 39 ] 8− polyoxomethalate (POM) structure as a thin‐film scaffold layer for CH 3 NH 3 PbI 3 ‐based perovskite solar cells (PSCs). A smooth nanoporous surface of POM causes outstanding improvement of the photocurrent density, external quantum efficiency (EQE), and overall efficiency of the PSCs compared to mesoporous TiO 2 (mp‐TiO 2 ) as scaffold layer. Average power conversion efficiency (PCE) values of 15.5 % with the champion device showing 16.3 % could be achieved by using POM and a sequential deposition method with the perovskite layer. Furthermore, modified and defect‐free POM/perovskite interface led to elimination of the anomalous hysteresis in the current–voltage curves. The open‐circuit voltage decay study shows promising decrease of the electron recombination in the POM‐based PSCs, which is also related to the modification of the POM/ perovskite interface and higher electron transport inside the POM layer.