The Effects of ZnTe:Cu Back Contact on the Performance of CdTe Nanocrystal Solar Cells with Inverted Structure

Bingchang Chen; Junhong Liu; Zexin Cai; Ao Xu; Xiaolin Liu; Zhitao Rong; Donghuan Qin; Wei Xu; Lintao Hou; Quanbin Liang

doi:10.3390/nano9040626

The Effects of ZnTe:Cu Back Contact on the Performance of CdTe Nanocrystal Solar Cells with Inverted Structure

Nanomaterials (Basel). 2019 Apr 17;9(4):626. doi: 10.3390/nano9040626.

Authors

Bingchang Chen¹, Junhong Liu², Zexin Cai³, Ao Xu⁴, Xiaolin Liu⁵, Zhitao Rong⁶, Donghuan Qin⁷, Wei Xu⁸, Lintao Hou⁹, Quanbin Liang^{10

11}

Affiliations

¹ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. ChenBC_999@163.com.
² School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. jhliu1@163.com.
³ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. 13005112535@163.com.
⁴ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. m13856403915@163.com.
⁵ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. liulin9708@163.com.
⁶ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. rzt1512388848@163.com.
⁷ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. qindh@scut.edu.cn.
⁸ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. xuwei@scut.edu.cn.
⁹ Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy Materials, Siyuan Laboratory, Department of Physics, Jinan University, Guangzhou 510632, China. thlt@jnu.edu.cn.
¹⁰ School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. l.quanbin@mail.scut.edu.cn.
¹¹ Institute of Polymer Optoelectronic Materials & Devices, State Key Laboratory of Luminescent Materials & Devices, South China University of Technology, Guangzhou 510640, China. l.quanbin@mail.scut.edu.cn.

Abstract

CdTe nanocrystal (NC) solar cells have received much attention in recent years due to their low cost and environmentally friendly fabrication process. Nowadays, the back contact is still the key issue for further improving device performance. It is well known that, in the case of CdTe thin-film solar cells prepared with the close-spaced sublimation (CSS) method, Cu-doped CdTe can drastically decrease the series resistance of CdTe solar cells and result in high device performance. However, there are still few reports on solution-processed CdTe NC solar cells with Cu-doped back contact. In this work, ZnTe:Cu or Cu:Au back contact layer (buffer layer) was deposited on the CdTe NC thin film by thermal evaporation and devices with inverted structure of ITO/ZnO/CdSe/CdTe/ZnTe:Cu (or Cu)/Au were fabricated and investigated. It was found that, comparing to an Au or Cu:Au device, the incorporation of ZnTe:Cu as a back contact layer can improve the open circuit voltage (V_oc) and fill factor (FF) due to an optimized band alignment, which results in enhanced power conversion efficiency (PCE). By carefully optimizing the treatment of the ZnTe:Cu film (altering the film thickness and annealing temperature), an excellent PCE of 6.38% was obtained, which showed a 21.06% improvement compared with a device without ZnTe:Cu layer (with a device structure of ITO/ZnO/CdSe/CdTe/Au).

Keywords: CdTe; Cu-doped; ZnTe; nanocrystal; solar cells; solution processed.