Silver‐Promoted High‐Performance (Ag, Cu)(In, Ga)Se2 Thin‐Film Solar Cells Grown at Very Low Temperature. Issue 5 (19th March 2021)

• Record Type: Journal Article
• Authors: Yang, Shih-Chi; Sastre, Jordi; Krause, Maximilian; Sun, Xiaoxiao; Hertwig, Ramis; Ochoa, Mario; Tiwari, Ayodhya N.; Carron, Romain
• Is Part Of: Solar RRL. Volume 5:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-19
• Subjects: Ag alloying -- (Ag, Cu)(In, Ga)Se2 -- Cu(In, Ga)Se2 -- interdiffusion -- low substrate temperatures -- VOC deficit; Solar energy -- Periodicals; Photovoltaic power generation -- Periodicals; Solar energy -- Research -- Periodicals; Photovoltaic power generation -- Research -- Periodicals; Periodicals; 333.7923
• DOI: 10.1002/solr.202100108
• Languages: English
• ISSNs: 2367-198X

Abstract

Abstract : Achieving high power conversion efficiencies with Cu(In, Ga)Se2 (CIGS) solar cells grown at low temperature is challenging because of insufficient thermal energy for grain growth and defect annihilation, resulting in poor crystallinity, higher defect concentration, and degraded device performance. Herein, the possibilities for high‐performing devices produced at very low temperatures (≤450 °C) are explored. By alloying CIGS with Ag by the precursor layer method, (Ag, Cu)(In, Ga)Se2 (ACIGS) solar cells grown at about 450 °C reach an efficiency of 20.1%. Only a small efficiency degradation (0.5% and 1.6% absolute) is observed for ACIGS absorbers deposited at 60 and 110 °C lower substrate temperature. CIGS devices exhibit a stronger efficiency degradation, driven by a decrease in the open‐circuit voltage ( V OC ). The root cause of the V OC difference between ACIGS and CIGS devices is investigated by advanced characterization techniques, which show improved morphology, reduced tail states, and higher doping density in ACIGS absorbers. The proposed approach offers several benefits in view of depositions on temperature‐sensitive substrates. Increased Cu diffusion promoted by Ag allows end‐point detection in the three‐stage process at the substrate temperatures below 300 °C. The modified process requires minimal modification of existing processes and equipment and shows the potential for the use of different flexible substrates and device architectures. Abstract : High‐performing (Ag, Cu)(In, Ga)Se2 (ACIGS) solar cells are fabricated at very low temperatures (≤450 °C). ACIGS devices outperform Cu(In, Ga)Se2 (CIGS) ones over a wide deposition temperature range: the efficiencies of 19.6% and 18.5% are achieved with the nominal substrate temperatures of 353 and 303 °C, respectively. The detailed comparison between the ACIGS and CIGS devices is investigated by different advanced characterization techniques.