External photoelectric effect of CsPb X 3 perovskite in X-ray region

As a novel low-cost semiconductor with extraordinary photoelectric property, the inorganic CsPbX3 perovskites have become emerging materials for the next generation of X-ray detectors in the past decade. However, most of recent studies of CsPbX3 perovskite X-ray detectors are based on their internal photoelectric effect. Though it is also important and widely used in vacuum X-ray detectors, the external photoelectric effect of CsPbX3 perovskite has been rarely studied by now. Thus, the response sensitivity of the CsPbX3 perovskite's external photoelectric effect in the X-ray region is studied in the present paper. First, a 230-nm-thick CsPbI2Br membrane is prepared on a metal substrate by a conventional one-step deposition method, with a precursor solution used. Then the external photoelectric responsivity and quantum efficiency of the CsPbI2Br membrane are calibrated in a range from 2000 to 5500 eV at Beijing Synchrotron Radiation Facility. The responsivity is over 5.1 x 10(-5) A/W in the range and the quantum efficiency is over 23%. These calibration data are close to those of a traditional X-ray photoelectric material CsI. The Monte-Carlo method is utilized to simulate the external photoelectric effect of CsPbI2Br perovskite, and the external photoelectric responsivity is calculated. The calculated data match well with the calibration, proving the Monte-Carlo method feasible for the external photoelectric effect simulation of CsPbX3 perovskite. Then the external photoelectric responsivities and quantum efficiencies of CsPbX3 perovskites are calculated via the Monte-Carlo method in the X-ray range from 2000 to 10000 eV. The calculated responsivities of different CsPbX3 perovskites are all close to the responsivity of CsI, and an order of magnitude higher than that of Au, and the CsPbX3 quantum efficiencies also follow a similar scenario. This indicates that CsPbX3 perovskites have good external photoelectric properties and potential applications in X-ray vacuum detectors such as photocathode and photomultiplier. The influence of thickness on CsPbX3 photoelectric response is also studied in this paper via Monte-Carlo simulation. The results show that the responsivity increases with the material thickness increasing, which is due to the increased X-ray absorption. The responsivities all reach their upper limits at a material thickness of about 150 nm, which means that the electrons generated at 150 nm can hardly escape from the material surface. It is indicated that the thickness of CsPbX3 should be no less than 150 nm to obtain the optimal photoelectric response.