Copper‐Doped InxGa2−xO3 Nanocrystals as Efficient Hole Transport Materials of Perovskite Solar Cells by Regulating Energy Levels

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The hole transport layers are critical for collecting holes and suppressing recombination in perovskite solar cells, and metal oxides are superior due to their green synthesis and good ambient stability. Although gallium oxide is rarely applied as the hole transport layers of devices for the mismatch of valence bands with perovskite materials, copper dopants can provide an additional transport channel via their impurity levels. Herein, InxGa2−xO3 nanocrystals with copper dopants are synthesized as the hole transport material of perovskite solar cells by the hydrothermal method, and uniform hole transport layers can be deposited by spin‐coating at a low temperature of 100 °C. The energy position of impurity levels and the hole transport ability of hole transport layers can be regulated by incorporating indium ions. In the optimized condition, the efficiencies of devices increase from 19.6% to 21.4%, which is related to the improvement of the charge extraction process and carrier recombination process. And the photostability of devices can be improved simultaneously. This work provides an efficient hole transport material for inverted perovskite solar cells and demonstrates the regulation of transport channels via impurity levels.