Solar Energy 213 (2021) 136–144 0038-092X/© 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. Encapsulation improvement and stability of ambient roll-to-roll slot-die-coated organic photovoltaic modules Ching-Yu Lee a , Cheng-Si Tsao a, b, * , Hua-Kai Lin a , Hou-Chin Cha a , Tsui-Yun Chung a , Yun-Ming Sung c , Yu-Ching Huang d, * a Institute of Nuclear Energy Research, Longtan, Taoyuan 32546, Taiwan b Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan c Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan d Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan A R T I C L E INFO Keywords: Organic photovoltaic Roll-to-roll Slot-die Module Encapsulation Stability ABSTRACT The manufacture of ambient roll-to-roll (R2R) slot-die-coated organic photovoltaic (OPV) is the basis toward commercialization of OPV. The low-cost large-area encapsulation technique of stability improvement of fexible OPV module is under-investigated. The related reports on fexible encapsulation up-scaled from cell were limited. The present study develops an effective and easy encapsulation method and architecture design based on the inverted structure of ambient R2R slot-die-coated PET/ITO/ZnO/active layer/hole transport layer (HTL)/Ag. All module areas are greater than 48 cm 2 . The P3HT:PCBM and PV2000:PC 71 BM adopted as active layers have the performance conversion effciencies of modules of 1–2.2% and 4.2%, respectively. The thermally-deposited MoO 3 and slot-die-coated PEDOT:PSS HTLs are used to compare the effect of HTL on T 80 lifetime of the large- area fexible R2R module under the accelerated test. The accelerated stability tests regarding to different encapsulation architectures, including damp-heat and light soaking stresses, were conducted. The intrinsic and extrinsic degradation effects are analyzed. We develop the simple encapsulation design effectively suppressing the lateral ingress of oxygen and moisture. The T 80 lifetime of P3HT:PCBM-based module can be improved to be 1500 h under the damp-heat test (65 ◦ C/65% RH). The T 80 lifetime of PV2000:PC 71 BM-based module can last for 7000 h under the dark and ambient environment (30 ◦ C/50 ± 20% RH). 1. Introduction The solution-processed polymer and organic photovoltaics (OPV) as potential next-generation PV have attracted much attention. The recent development in power conversion effciency (PCE) of the laboratory- scale single-junction OPV cell demonstrates a rapid progress, exceeding 15% (Cui et al., 2019). One of advantages of OPV technology is the large-area module manufacture with fast speed, high-throughput, low-cost and simple coating or printing methods. Furthermore, the mass production lines using ambient roll-to-roll (R2R) coating on fexible PET substrate and low-cost materials enables signifcant cost reduction for OPV module compared to the other PV technologies (Angmo et al., 2014), being a critical factor toward commercialization of OPV. The fexible and light-weight R2R-coated OPV modules can offer a variety of diverse applications and commercial opportunities from portable smart electronics and IOT sensors to building-integrated PV. However, there is still a gap from the laboratory scale to the industrial manufacture. The scaling up of OPV module manufacture cause the severe challenges on the control of coating parameters and flm/layer interface structure, leading the substantial reduction in performance and bottleneck toward commercialization. Few laboratories or manufacturers devoted to commercial OPV module manufacture. According to the literature (Berny et al., 2016; Lucera et al., 2016), the current PCE of fexible solution-coated polymer solar cell modules with a size of ~100 cm 2 is close to ~5%. Another bottleneck of OPV commercialization is the stability. The cost, stability and PCE of OPV are usually trade-off. The stability and PCE of large-area OPV module cannot be improved in parallel due to the complex combination and mutual interference of several factors such as the used materials, processing and architecture etc. The PCE of the * Corresponding authors at: Institute of Nuclear Energy Research, Longtan, Taoyuan, 32546, Taiwan (C.-S. Tsao). Ming Chi University of Technology, New Taipei City 24301, Taiwan (Y.-C. Huang). E-mail addresses: cstsao@iner.gov.tw (C.-S. Tsao), huangyc@mail.mcut.edu.tw (Y.-C. Huang). Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener https://doi.org/10.1016/j.solener.2020.11.021 Received 15 June 2020; Received in revised form 19 October 2020; Accepted 7 November 2020