H <sub>x</sub>MoO <sub>3-Y</sub> Nanobelts: An Excellent Alternative to Carbon Electrode for High Performance Mesoscopic Perovskite Solar Cells

Abstract

The forming Schottky barrier between carbon and perovskite has currently been the bottlenecks to improve the performance of carbon-based hole-conductor-free perovskite solar cells (C-PSCs). A conventional approach to resolving this issue is incorporating a hole-transport material (HTM) in the mesoscopic skeleton or chemical modification of the carbon electrode. Here, we show an innovative strategy that using solution-processed hydrogen molybdenum bronzes (HxMoO3-y) nanobelts, an n-type HTM with high work function and electrical conductivity, as the sole electrode material to enhance the hole-extraction process and result in efficient PSCs for the first time. The mesoscopic cell configuration of FTO/c-TiO2/m-TiO2/m-Al2O3/HxMoO3-y with perovskite infiltration delivered a champion power conversion efficiency (PCE) of 14.5%, which compares favorably with that of 13.3% for the typical high temperature C-PSCs. The increase in cell efficiency stems primarily from the enhancement in open circuit voltage and short circuit current, which is owed to the HxMoO3-y electrode with more favorable energy alignment and higher hole-extraction ability than carbon electrode. These results open up the potential of HxMoO3-y nanobelts as an efficient electrode for realizing high-performance and low-cost mesoscopic PSCs.