Significantly Enhanced Detectivity of CIGS Broadband High-Speed Photodetectors by Grain Size Control and ALD-Al2O3 Interfacial-Layer Modification

Ye Yuan; Linquan Zhang; Genghua Yan; Guobiao Cen; Yujin Liu; Longlong Zeng; Chunhong Zeng; Chuanxi Zhao; Ruijiang Hong; Wenjie Mai

doi:10.1021/acsami.9b04248

Significantly Enhanced Detectivity of CIGS Broadband High-Speed Photodetectors by Grain Size Control and ALD-Al₂O₃ Interfacial-Layer Modification

ACS Appl Mater Interfaces. 2019 Jun 5;11(22):20157-20166. doi: 10.1021/acsami.9b04248. Epub 2019 May 22.

Authors

Affiliations

¹ Siyuan Laboratory, Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy Materials, Department of Physics , Jinan University , Guangzhou 510632 , P. R. China.
² Institute of Solar Energy Systems, Guangdong Provincial Key Laboratory of Photovoltaic Technology, School of Physics , Sun Yat-sen University , Guangzhou 510006 , P. R. China.

PMID: 31070353
DOI: 10.1021/acsami.9b04248

Abstract

The Cu(In,Ga)Se₂ (CIGS) thin film has been commercialized as solar cells with great success, but its application for photodetectors still faces some practical challenges, including low detectivity and long response time. In this paper, the structure of the Mo/CIGS/CdS/ZnO/ITO heterojunction has been fabricated, and satisfactory performances of high detectivity and fast response time have been achieved by suppressing the dark current and enhancing the carrier mobility. The controllable growth of CIGS grains is accomplished through optimizing the selenization process, demonstrating that bigger grain sizes resulted in higher carrier mobility and better response characteristics. Particularly, the high rise/decay speed of 3.40/6.46 μs is achieved. Furthermore, the interface of the CIGS/CdS heterojunction has been modified by the Al₂O₃ layer via the atomic-layer deposition (ALD) process. The dark current of the device is effectively suppressed by the ALD-Al₂O₃ layer, which remarkably drops from ∼10^-7 to ∼10^-9 A. As a consequence, the detectivity rises from 3.08 × 10¹¹ to 1.84 × 10¹² Jones. In addition, the ALD-Al₂O₃ layer shows a protective effect as well, which is positive for photoelectrical conversion. Besides, the wide linear dynamic range of 102.1 dB and large -3 dB bandwidth of 78 kHz are acquired. This work suggests that the CIGS-based heterojunction has great potential for high-performance thin-film photodetectors.

Keywords: AlO interfacial layer; CIGS heterojunctions; atomic-layer deposition; high detectivity; self-powered; thin-film photodetectors.