CFN Colloquium

Metal halide perovskite semiconductors are emerging low-cost materials for photovoltaics, light emitting devices and detectors. Because of the inclusion of high atomic numbered elements, perovskites are promising candidates for high efficiency X-ray sensing. In this talk, I will discuss the properties of perovskite semiconductors for X-ray and visible photon sensing. Firstly, we report a long carrier diffusion length in 2D perovskite single crystals, assisted by the shallow trap and de-trapping process. Next, we show that such a long diffusion length ensures a full charge collection after charge ionization, which is beneficial for detectors for X-ray and visible photons. In addition, we have found the shallow trap also extend the carrier transport lifetime that facilitate a charge multiplication in the detector driven under high voltages. Such a process introduces a photo conductivity gain, leading to an unusually high X-ray and visible photon sensing efficiency. A high gain can be also achieved by building a hetero-structured device. Interfacing perovskites with a high mobility channel, such as graphene or n-type GaN can also multiplicate the photo-generated carriers. With a hetero-structured device, we show a high X-ray sensitivity over 108 µCGy-1cm-2. Short bio: Dr. Wanyi Nie graduated from Wake Forest University with a Ph.D. degree in Physics Department in late 2012. Her Ph.D. thesis was about the optimization of organic photovoltaics. She later joined Los Alamos National Laboratory (LANL) working on hybrid semiconductors, such as hybrid perovskites and metal organics. Since Jan.2024, she started her new group at SUNY University at Buffalo as an associate professor at the Department of Physics. Her group are working on developing novel opto-electronic devices using nanocrystal, organics and hybrid perovskites. Recently, the team mainly focus on perovskites and chiral materials for sensing radiation photon, polarized light. Her team are also developing light emitting devices.