title: Novel p-Type Conductive Semiconductor Nanocrystalline Film as the Back Electrode for High-Performance Thin Film Solar Cells.
abstract: Thin film solar cells, due to the low cost, high efficiency, long-term stability, and consumer applications, have been widely applied for harvesting green energy. All of these thin film solar cells generally adopt various metal thin films as the back electrode, like Mo, Au, Ni, Ag, Al, graphite, and so forth. When they contact with p-type layer, it always produces a Schottky contact with a high contact potential barrier, which greatly affects the cell performance. In this work, we report for the first time to find an appropriate p-type conductive semiconductor film, digenite Cu9S5 nanocrystalline film, as the back electrode for CdTe solar cells as the model device. Its low sheet resistance (16.6 Ω/sq) could compare to that of the commercial TCO films (6-30 Ω/sq), like FTO, ITO, and AZO. Different from the traditonal metal back electrode, it produces a successive gradient-doping region by the controllable Cu diffusion, which greatly reduces the contact potential barrier. Remarkably, it achieved a comparable power conversion efficiency (PCE, 11.3%) with the traditional metal back electrode (Cu/Au thin films, 11.4%) in CdTe cells and a higher PCE (13.8%) with the help of the Au assistant film. We believe it could also act as the back electrode for other thin film solar cells (α-Si, CuInS2, CIGSe, CZTS, etc.), for their performance improvement.
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Ming-Jian
authors.initials: MJ
authors.lastname: Zhang
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Qinxian
authors.initials: Q
authors.lastname: Lin
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Yang
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Zongwei
authors.initials: Z
authors.lastname: Mei
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Liang
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School , Shenzhen 518055, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
keywords: Cu9S5 nanocrystal; back electrode; energy level matching; high electrical conductivity; p-Type conductive semiconductor film; thin film solar cells