Different photocurrent response of Cs4PbBr6 particles

Abstract

Zero-dimensional (0D) all-inorganic cesium lead halide perovskites, particularly Cs4PbBr6, have been attracting wide attention due to their excellent optical properties and stability. The research also focuses on the origin of green emission from Cs4PbBr6 which has a bandgap located at UVB region. From now on, both Cs4PbBr6 without visible emission and with green emission have been successfully prepared, however, the origin of green emission remains controversial. Photocurrent response is one of the effective approaches to explore how the photo-excited carriers influence the photo-physical properties of materials. In our study, Cs4PbBr6 particles without visible emission and with green emission were synthesized and their photocurrent response was investigated. The former showed positive photocurrent response, while the latter showed negative photocurrent response. The negative response was believed to be due to a built-in electric field constructed by the charged excitons in green-emissive Cs4PbBr6. From our calculation, numerous vacancies of Br is easier to appear in green-emissive Cs4PbBr6 lattice, which could combine the neutral excitons to form charged excitons. This work may contribute to the explanation of the origin of green emission of Cs4PbBr6 to some extent.

Negative Photoconductivity: Bizarre Physics in Semiconductors

“…Metal halide perovskites are widely explored in photodetection applications. ,− The charge carrier generation under illumination leads to positive photoconductivity in these materials. A lot of reports demonstrate the PPC in perovskite materials. − Recently, the NPC was reported in halide perovskites under certain conditions. − In this line, Yuan et al presented the NPC under illumination in Cs 4 PbBr 6 perovskite single crystals . A significant amount of reduction was observed in the current under illumination than in the dark current.…”

“…As we discussed in the above sections that NPC was widely observed in various types of materials. ,,,,− Different origin has been proposed for NPC generation, which can be suitable for various kind of applications. The NPC effect has been used for the fabrication of humidity and light sensors, highly sensitive photodetectors, and nonvolatile memories. ,− Qin et al demonstrated that the NPC in nanodiamonds can be applied for humidity sensors with the sensitivity of 1.26 × 10 6 %, which is the highest in carbon-based humidity sensors . Zhuang et al showed the application of NPC in humidity sensors with a responsivity of 418.1 μAW –1 (at high humid RH = 90%) .…”