Quasi-ohmic contact formation assisted by the back contact with Cu2Te nanoparticles@reduced graphene oxide composites for highly efficient CdTe solar cells

Abstract

Composite materials based on reduced graphene oxide decorated with cuprous telluride nanoparticles (Cu2Te NPs@rGO) were fabricated using a facilitated two-step method. A back-contact layer was formed using a spin-coating method for cadmium telluride (CdTe) solar cells. This research is aimed to improve the photovoltaic performance of a device containing Cu2Te NPs@rGO/Au back contacts. Cu2Te NPs, as the active copper diffusion source, dope and passivate the interfaces and grain boundaries of CdTe to form the p+-layer, which can reduce the recombination centers and back-contact barrier height. Simultaneously, the reduced graphene oxide (rGO), as a buffer and carrier transport layer, prevents excessive copper diffusion during the annealing process and improves the hole collection capacity. The p-type layer formed by the rGO contact with the Au film enhances hole transport and facilitates a low-resistance contact formation, forming a quasi-ohmic contact, and increases the open-circuit voltage and short-circuit current density. Cu2Te NPs@rGO/Au back contacts significantly improved the photovoltaic performance (Eff: 16.5%, Voc: 830 mV, Jsc: 27.13 mA/cm2, fill factor: 73.3%, area: 0.24 cm2). The composites retain properties of Cu2Te NPs and rGO. Their multifunctional properties reveal the potential of Cu2Te NPs@rGO as the back contact and broaden the application of graphene-based composites in photovoltaic devices. Additionaly, the preparation of graphene-based composites and their application as back contact is simple and convenient.