Surface and bulk contributions to electrical behavior of cesium lead bromide (CsPbBr3) single crystal

Abstract

Halide perovskite single crystals (SCs) are becoming increasingly popular in the field of optoelectronics due to their superior properties compared to polycrystalline thin films. This is believed to be due to a lower concentration of defects in SCs. Research into the surface and bulk properties of SCs has been a focus area since their discovery. It can be challenging to investigate the surface and bulk properties of perovskite solar cells (PSCs) SCs. This study used impedance spectroscopy (IS) to differentiate between the surface and bulk electrical responses of cesium lead bromide (CsPbBr3) SCs, which is a technique that has been infrequently used in previous reports. This study examined the electrical response of CsPbBr3 solar cells (SCs) by measuring the Nyquist plots and capacitance-frequency responses under different optical excitations. The data collected under blue and red wavelengths were analyzed and compared, revealing that the photocurrent and capacitive response were stronger under blue light (λB) than under red light (λR). This systematic examination of the electrical response under different optical excitations has not been done before. This study observed that the low-frequency capacitance changes less under blue light than under red light. The reason for this difference is thought to be caused by the polarization of the interface between the metal contacts and the surface of the PSCs (SCs) or by the presence of defects in the SCs that affect conductivity. The rapid collection of carriers from the surface under λB means that they do not contribute to the increase in capacitance with temperature. As far as the authors are aware, investigations of the electrical responses of SCs, such as impedance and capacitance, under various illumination wavelengths and temperatures are uncommon in the bibliography.