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 (R_c). However, carrier doping in halide perovskites has remained elusive, and selective contact doping has not been achieved, resulting in excessive R_c 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 R_c of 26-70 Ω cm and a notably high two-terminal sheet conductance exceeding 225 µS at 190 K.