In situ, seed-free formation of a Ruddlesden–Popper perovskite Cs2PbI2Cl2 nanowires/PbI2 heterojunction for a high-responsivity, self-powered photodetector

Abstract

As the necessary precursor of emerging lead-halide perovskite materials, PbI₂ is also promising for optoelectronic devices, such as photodetectors (PDs). Herein, the novel Ruddlesden–Popper (RP) perovskite Cs₂PbI₂Cl₂ nanowires are grown onto PbI₂ film by an in situ, seed-free solution method to build a Cs₂PbI₂Cl₂ nanowires/PbI₂ heterojunction, wherein the stress-induced diffusion mechanism is proposed for its formation. Furthermore, the heterojunction is used to fabricate the low-cost, simple-structure self-powered PD, which exhibits a responsivity (R) peak of 0.17 A W⁻¹, a specific detectivity (D*) maximum of 3.02 × 10¹² Jones, and a fast response speed of 0.95 μs. These performance parameters are much better than those of a similar PD based on the pristine PbI₂ film and even superior to most of PbI₂-based PDs reported earlier. The greatly improved performance of the self-powered PD with the Cs₂PbI₂Cl₂ nanowires/PbI₂ heterojunction is largely related to the suppressed carrier recombination and enhanced carrier transportation, as a result of the enlarged built-in field (E_b) by the heterojunction. Hence, our work provides a scientific basis for exploiting high-performance PDs by combining PbI₂ with novel perovskite materials.