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

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 x 10(12) Jones, and a fast response speed of 0.95 mu s. 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.