Solution‐Processed Copper‐Doped Chromium Oxide with Tunable Oxygen Vacancy for Crystalline Silicon Solar Cells Hole‐Selective Contacts

Compared with vacuum evaporation, metal oxides deposited by solution process exhibit advantages, for example, dopants can be easily incorporated in a wide range and the contents are easy to be regulated by changing the composition of precursors. Herein, solution‐processed p‐type copper‐doped chromium oxide (Cu:CrO_x) films with tunable oxygen vacancy are demonstrated via a postannealing process. The synthetic and postannealing temperature have a significant impact on the chromium cation oxidation state in the Cu:CrO_x films, leading to the variation of work function for the oxide films. By adjusting the work function of Cu:CrO_x films, a low contact resistivity of 95 mΩ cm² can be realized for the Ag/Cu:CrO_x/p‐Si contact. Finally, the optimized Cu:CrO_x films are used as the hole transporting layer in c‐Si solar cells, showing an increased power conversion efficiency from 15.2% (without Cu:CrO_x) to 16.9% (with Cu:CrO_x). The results show an effective stage to use p‐type metal oxides as a hole‐selective layer in c‐Si solar cells.