Surface passivation and band engineering: a way toward high efficiency graphene–planar Si solar cells

Surface passivation and band engineering: a way toward high efficiency graphene–planar Si solar cells†

Chao Xie,‡^ab Xiaozhen Zhang,‡^a Yiming Wu,^a Xiujuan Zhang,*^a Xiwei Zhang,^a Yan Wang,^a Wenjun Zhang,*^c Peng Gao,^a Yuanyuan Han^a and Jiansheng Jie*^a

Author affiliations

* Corresponding authors

^a Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou, Jiangsu 215123, P.R. China
E-mail: jsjie@suda.edu.cn, xjzhang@suda.edu.cn

^b School of Materials Science and Engineering, Hefei University of Technology, Hefei, Anhui, P.R. China

^c Center Of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong Special Administrative Region, China
E-mail: apwjzh@cityu.edu.hk

Abstract

Graphene–Si Schottky junction solar cells are promising candidates for high-efficiency, low-cost photovoltaic applications. However, their performance enhancement is restricted by strong carrier recombination and relative low barrier height. Here, we demonstrated the successful construction of high-efficiency graphene–planar Si solar cells via modification of the Si surface with a molecule monolayer as well as tuning the interface band alignment with an organic electron blocking layer. Methylated Si showed the capability to effectively suppress the surface carrier recombination, leading to a remarkable improvement of device efficiency. The recombination was further reduced by inserting a thin P3HT organic layer; the unique band alignment could prevent electron transfer from n-Si to the graphene anode so as to minimize the current leakage. These methods, along with careful control of the graphene doping level and layer number, gave rise to a power conversion efficiency (PCE) as high as 10.56%. The scalability of the devices was further investigated by studying the device area dependent photovoltaic performance.