Bulk-heterojunction doping in lead halide perovskites for low-resistance metal contacts.

Efficient carrier injection at metal-semiconductor interfaces is essential for probing intrinsic electronic properties and enabling high-performance devices. Thinning the Schottky barrier via contact doping is a cornerstone strategy in semiconductor technology for minimizing contact resistance (Rc). However, carrier doping in halide perovskites has remained elusive, and selective contact doping has not been achieved, resulting in excessive Rc that far exceeds the intrinsic material resistance. Here we report an effective contact-doping strategy by transferring Ag/Au electrodes onto single-crystal CsPbBr3 thin films using a low-energy van der Waals integration process. Moderate annealing (80-180 °C) during transfer enables silver diffusion into CsPbBr3, followed by its transformation into Ag2O clusters upon ultraviolet treatment, forming an Ag2O/CsPbBr3 bulk heterojunction. The Ag2O clusters embedded in CsPbBr3 act as interfacial electron acceptors, inducing a local hole density of ∼5 × 1017 cm-3 in the contact region. This markedly shrinks the Schottky barrier and enhances carrier injection, yielding a substantially reduced Rc of 26-70 Ω cm and a notably high two-terminal sheet conductance exceeding 225 µS at 190 K.