In inverted perovskite solar cells (PSCs), metal oxides become kind of promising hole transport layers for their facile synthesis and low cost. For conventional hole transport materials, the valence band match between metal oxides and perovskite layers is usually necessary for the hole extraction process. Ga₂O₃ is an emerging semiconductor material with ultrawide bandgap, but a significant energy level mismatch exists at Ga₂O₃/perovskite interfaces. In this work, Cu-doped Ga₂O₃ (Ga₂O₃:Cu) nanocrystals are synthesized by the hydrothermal method and used as the hole transport material of inverted PSCs for the first time. It is found that Cu dopants can substantially improve the performance of Ga₂O₃ layers, and the efficiency of PSCs is increased from 7.6% to 19.5%. This improvement can be attributed to the additional hole transport channels from impurity levels of Cu dopants, which exactly match with the valence band of perovskite layers. As a consequence, Ga₂O₃:Cu layers can effectively extract holes and inhibit the recombination in perovskite layers. This work also provides an alternative route for the design of hole transport materials.