X-ray-Voltaic Effect in the Single Crystals of CH₃NH₃PbI₃ Perovskite

This work evaluates the feasibility of an X-ray-voltaic element based on a CH₃NH₃PbI₃ perovskite single crystal, which combines excellent scintillation and photovoltaic properties. It was demonstrated that the X-ray-voltaic effect in this material can only be achieved if the sample is transformed from its initial antiferroelectric state to a ferroelectric state through exposure to intense UV light. The observed generation of free current carriers is explained by a combination of two effects─the direct X-ray-to-current conversion and the conventional PV effect generated due to excitonic X-ray luminescence. The crucial role of the second mechanism is confirmed by the observed temperature changes in the photocurrent density, which was found to be proportional to the intensity of the excitonic luminescence band. It was also shown that ionic conductivity arising in the sample mostly under the influence of light photons partially compensates the flow of the free electrons and holes generated due to the conventional PV and X-ray-voltaic effects. Although the value of the generated power at room temperature in the proposed device was found to be considerably lower in comparison with those for the best X-ray-voltaic batteries based on the semiconductor p-n-junctions, it has been shown that its photoresponse increases 2 orders of magnitude at low temperatures. Besides, the technology of its manufacturing is considerably simpler and cheaper. Moreover, the significant increase in the photocurrent at cryogenic temperatures offers a crucial advantage when the proposed power cell is applied in outer space.