All Dry Process with K2S Post Deposition Treatment by Atomic Layer Deposition: A Feasible Way for Large-Scale Production of Alkali Post Treatment in CIGS Thin Film Solar Cell Industry

• Main Authors: Liu, Jun-Nan, Chen, Bo-Shiun, Chung, Chia-Chen, Yang, Tzi-Yi, Chang, Yung-Ling, Tsai, Ji-Shian, Lin, Tzu-Ying, Cheuh, Yu-Lun, Lai, Chih-Huang
• Format: Conference Proceeding
• Language: English
• Subjects: Atomic layer deposition; Industries; Metals; Photovoltaic cells; Photovoltaic systems; Potassium; Production; Spontaneous emission; Sputtering; Surface treatment
• ISSN: 2995-1755
• DOI: 10.1109/PVSC57443.2024.10748984

Heavy alkali metal post-treatment is a key factor in enhancing the efficiency performance of Cu(In, Ga)(Se, S)2 (CIGSSe) solar cells. The usual method using alkali metal fluoride evaporation for post-treatment arise challenges in achieving large-area and uniform thin film deposition. To address this issue and fulfill alkali metal post-treatment on CIGSSe solar cell industry with the advantages of large-scale, uniform and simple process, this study is the first time to propose a novel approach called atomic layer deposition (ALD) and a new potassium source called potassium disulfide (K2S). ALD-grown K2S post-deposition treatment (PDT) on large-area (8*8cm 2 ) CIGSSe solar cell boosts the device efficiency from 16.04% to 18.24%. SIMS, XPS, and HRTEM confirm the additional K incorporation into the CIGSSe absorber after K2S-PDT. Moreover, the first-time observation of KInSe2 secondary phase on absorber surface from SAED pattern indicates that K2S post-deposition treatment indeed modifies the chemical state and electronic structure of the absorber surface and probably passivates the interface. Additionally, the reduction in carrier recombination at the CIGSSe/buffer interface and within the CIGSSe bulk are evidenced by SunsVOC. The K2S-PDT demonstrated by ALD proposed in this study not only achieves efficiency enhancement comparable to traditional KF-PDT but also integrates the processes of alkali metal doping and buffer layer deposition within the same ALD equipment. Finally, this work highlights the further simplification, all dry-process and efficiency-boost of CIGSSe module manufacturing.