title: Room-Temperature Chemical Solution Treatment for Flexible ZnS(O,OH)/Cu(In,Ga)Se2 Solar Cell: Improvements in Interface Properties and Metastability.
abstract: We demonstrate an effective room-temperature chemical solution treatment, by using thioacetamide (S treatment) or thioacetamide-InCl3 (In-S treatment) solution, on Cu(In,Ga)Se2 (CIGSe) surface to engineer the ZnS(O,OH)/CIGSe interface and junction quality, leading to enhanced efficiency and minimized metastability of flexible solar cells. The control device without treatment reveals a relatively low efficiency of 8.15%, which is significantly improved to 9.74% by In-S treatment, and 10.39% by S treatment. Results of X-ray photoelectron spectroscopy suggest that S is incorporated into CIGSe surface forming CIGSSe by S treatment, whereas a thin In-S layer is formed on CIGSe surface by In-S treatment with reduced amount of S diffusing into CIGSe. PL spectra and TRPL lifetime further reveal that S incorporation into CIGS surface may substitute the OSe and/or directly occupy the vacant anion site (VSe), resulting in the effective passivation of the recombination centers at CIGSe surface. Moreover, reducing the concentrations of VSe may thereby decrease the density of (VCu-VSe) acceptors, which can minimize the metastability of ZnS(O,OH)/CIGSe solar cells. With S treatment, the light soaking (LS) time of ZnS(O,OH)/CIGSe device is reduced approximately to one-half of control one. Our approach can be potentially applied for alternative Cd-free buffer layers to achieve high efficiency and low metastability.
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Wei-Hao
authors.initials: WH
authors.lastname: Ho
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Hsu
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Tzu-Hsuan
authors.initials: TH
authors.lastname: Yeh
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Chang
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Shih-Yuan
authors.initials: SY
authors.lastname: Wei
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Tzu-Ying
authors.initials: TY
authors.lastname: Lin
authors.affiliation: Department of Material Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China.
authors.forename: Chih-Huang
authors.initials: CH
authors.lastname: Lai
keywords: CIGS solar cells; Cd-free buffer; ZnS(O,OH) buffer; interface; light soaking; metastability; passivation; surface treatment