Enhanced Photodetection of Monocrystalline CsPbBr₃ Photoconductor Enabled by Largely Variable Contact Resistance of Graphene Electrodes.

Abstract

Excellent photoelectric properties and stability of CsPbBr₃ single crystals mark broad prospects in the fields of photoelectrical detection. While attention to the contacts that have a huge influence on the figures of merit of the devices is relatively lacking, making an investigation into high-quality contacts a pressing need. Here, transparent multilayer graphene electrodes (MGE) are directly laminated to CsPbBr₃ single crystals, forming a photoconductor-type photodetector. Benefiting from the optical transparency, mechanical flexibility, and chemical stability of multilayer graphene (MG) and its appropriate energy band alignment with CsPbBr₃, the MG-contacted photoconductor exhibits significantly reduced dark current, enhanced photocurrent, and improved operational stability compared to its Au-contacted counterpart. Schottky barrier height at the MG-CsPbBr₃ interface varies under different illuminations owing to the transparency of MG, enabling variable contact resistance (<i>R</i>_C) over a wide range and thereby an approximately 2 orders of magnitude enhancement in the light-to-dark ratio of the MG-contacted photoconductor. Enhanced detectivity under weak illumination and an improved response rate are also achieved. Furthermore, the chemical inertness of carbon-based multilayer graphene electrodes brings about a pronounced suppression of photocurrent drift. The transparent MGE provides a method for achieving wide-range changes in contact resistance to realize photodetection and also offers a feasible approach for the assembly of efficient and stable perovskite optoelectronics.