Highly efficient photoelectric effect in halide perovskites for regenerative electron sources

Abstract

Electron sources are a critical component in a wide range of applications such as electron-beam accelerator facilities, photomultipliers, and image intensifiers for night vision. We report efficient, regenerative and low-cost electron sources based on solution-processed halide perovskites thin films when they are excited with light with energy equal to or above their bandgap. We measure a quantum efficiency up to 2.2% and a lifetime of more than 25 h. Importantly, even after degradation, the electron emission can be completely regenerated to its maximum efficiency by deposition of a monolayer of Cs. The electron emission from halide perovskites can be tuned over the visible and ultraviolet spectrum, and operates at vacuum levels with pressures at least two-orders higher than in state-of-the-art semiconductor electron sources.

Cesium-Coated Halide Perovskites as a Photocathode Material: Modeling Insights

“…However, once a Cs coating is added, systems containing I and terminated with a [001] surface have the lowest work functions. These results are in good agreement with the recent experimental demonstration of Cs-coated perovskite materials as photocathode devices, 37 and the insights gained here can further be used for material development. A phenomenological model was developed to predict the work function with the material, surface coverage, and surface termination.…”

“…In order to lower the work function into the optical region for more affordable operating conditions, one technique is to add a coating of Cs. Indeed, recently reported efficient free-electron emission halide perovskite thin films operating in the visible to the ultraviolet spectral range for the first time further motivate in-depth computational studies on this emergent application.…”

“…Here we use density functional theory (DFT) to investigate the photocathode performance of Cs-coated halide perovskites. Many current photocathodes utilize Cs coatings to lower the work functions of photocathode materials due to the low electron affinity of Cs. − In this study, we specifically focus on Cs-coated CsPbX 3 , where X is a halide (Br or I). We consider the influence of surface termination, coating thickness, and material composition on the work function, electronic and optical properties, and Cs adsorption energy of these perovskites.…”

A Theoretical Framework for Microscopic Surface and Interface Dipoles, Work Functions, and Valence Band Alignments in 2D and 3D Halide Perovskite Heterostructures

“…Coating perovskite surfaces with a metal like Cs presents potential technological promises in applications requiring electron sources such as electron beam accelerator facilites. 28 It has recently been demonstrated that by depositing monolayers of Cs on top of halide perovskites, the electron emission efficiency was improved 29 and the improvement was attributed to a change of sign of the electron affinity, which translates into a diminishing work function. 1).…”

Physically inspired deep learning of molecular excitations and photoemission spectra

“…The photoelectric effect 1 describes the response of molecules and materials to electromagnetic radiation by emission of electrons. This effect plays a fundamental role in daily life, but also in cutting-edge technology, such as optoelectronic devices, 2,3 regenerative electron sources for free-electron lasers, 4 or photovoltaics, for instance to design artificial ion pumps that mimic nature. 5 …”