Roll-to-Roll prepared flexible antireflection film with microstructure for photovoltaic applications Min Wang, Pengsha Ma, Dongdong Li, Shanghai Advanced Research Institute, Chinese Academy of Sciences E-mail: [email protected] Optical management in photovoltaic devices is crucial for improving their efficiency. Inspired by the structure of moth eye, anti-reflection (AR) films with gradient of effective refractive index have been achieved by one-dimensional arrayed nanostructures [1-4]. However, the nanoscaled structures are encountering poor mechanical strength, which cannot meet the challenge of harsh condition outside. Herein, we report a flexible AR film with microscaled structure through roll-to-roll fabrication process (Figure 1a), which delivered enhanced light harvesting capability for solar cells with stronger mechanical strength. The AR film was attached onto the surface of a triple junction thin film silicon solar cell (a-Si) by a lamination process (Figure 1b). A broadband decreased reflectance was achieved compared to the one without AR film (Figure 2a), which is further verified by the quantum efficiency (QE) and I-V measurements (Figure 2b and 2c). The significance of AR film is positively correlated with the increased incident angle. As the incident angle increased, the η for both cells with and without AR film was reduced, while the relative improvement of η gradually increases from 3.7% to 11.5% when the incident angle increases from 0°to 60°(Figure 2d). In brief, the proposed AR films apparently improved the efficiency of solar cells, with the advantages of higher mechanical strength and easier fabrication process. This possesses great potential for large scale deployment on photovoltaic panels with both flexible and rigid substrates. References  H.-C. Chang, K.-Y. Lai, Y.-A. Dai, H.-H. Wang, C.-A. Lin, J.-H. He, Nanowire arrays with controlled structure profiles for maximizing optical collection efficiency, Energy Environ. Sci., 4 (2011) 2863-2869.  Z. Fan, R. Kapadia, P.W. Leu, X. Zhang, Y.-L. Chueh, K. Takei, K. Yu, A. Jamshidi, A.A. Rathore, D.J. Ruebusch, M. Wu, A. Javey, Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption, Nano Lett., 10 (2010) 3823-3827.  D. Yu, M. Yin, L. Lu, H. Zhang, X. Chen, X. Zhu, J. Che, D. Li, High-Performance and Omnidirectional Thin-Film Amorphous Silicon Solar Cell Modules Achieved by 3D Geometry Design, Adv Mater, (2015).  Q. Lin, B. Hua, S.-f. Leung, X. Duan, Z. Fan, Efficient Light Absorption with Integrated Nanopillar/Nanowell Arrays for Three-Dimensional Thin-Film Photovoltaic Applications, ACS nano, 7 (2013) 2725-2732. Figure 1. Schematics of AR film fabrication with roll-to-roll process and AR film attached on solar cell. α (located in yoz plane) and β (located in xoz plane), represent the incident light angle. Figure 2. (a) Reflectance spectra of a-Si solar cell with and without AR film. (b) QE measurement of a-Si solar cell with and without AR film, which contains three overlapped cells, top cell, middle cell, bottom cell. (c) J-V measurements of a-Si solar cell with and without AR film at 0 and 60 degrees of incident light (α). (d) η of a-Si solar cell with and without AR film obtained at different angles (α), together with the angular-dependent relative improvement of η.