High-performance vertical graphene nanowall/silicon Schottky junction solar cells with Nafion doping and plasma etching

Abstract

In this paper, a solar cell based on the vertical graphene nanowall (VGNW)/silicon Schottky junction is doped by polymeric acid (Nafion) and exhibits a high power-conversion efficiency after Ar plasma etching. It is found that, the Nafion doping scheme effectively increases the WF of VGNW films by ∼0.5 eV, and simultaneously reduces its average reflectance to ∼28%. However, there appears to be a poor-conductive Nafion capping layer on the VGNWs after doping, which severely influences the carriers electrical transportation. When a plasma etching process is introduced, the VGNWs buried in the Nafion polymers are exposed, thus reducing its sheet resistance by ∼20%. The combination of Nafion doping and plasma etching makes the Vbi of the VGNW/n-Si heterojunction greatly improve and exceed 0.6 V, and the FF factor of the VGNW/n-Si solar cells increases from 55.8% to 62.9%. Applying interface passivation and light management, we achieve a significant gain of Jsc and a well-performance VGNW/n-Si Schottky junction solar cell (Voc of 523 mV, FF of 57.1% and Jsc of 30.8 mA/cm2), whose PCEs up to 9.2% (AM 1.5 G). The present device architecture design and optimisation scheme here are envisaged to be potentially valuable for the doping modification of other 3D materials with similar structures.