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An Easily Accessible Cathode Buffer Layer for Achieving Multiple High Performance Polymer Photovoltaic Cells
- Zhao, Wenchao, Ye, Long, Zhang, Shaoqing, Yao, Huifeng, Sun, Mingliang, Hou, Jianhui
- The Journal of Physical Chemistry C 2015 v.119 no.49 pp. 27322-27329
- barium, cathodes, lighting, photovoltaic cells, physical chemistry, polymers, transmittance
- Here we report a successful efficiency improvement strategy in both conventional and inverted polymer solar cells (PSCs) based on multiple polymer blends, using a feasible and commercially available cathode buffer layer (CBL), namely barium hydroxide [Ba(OH)₂], to modify the photoactive blend and cathode contacts. High performance PSCs with an identical Ba(OH)₂ buffer layer were fabricated based on the multiple light-harvesting PBDT-TS1:PC₇₁BM, PffBT4T-2OD:PC₇₁BM, and PBDT-TS1:N2200 blends. The conventional PSC with Ba(OH)₂ as the CBL showed a higher power conversion efficiency (PCE) of 9.65% based on the PBDT-TS1:PC₇₁BM system under the illumination of 100 mW/cm². For the inverted cells based on the PffBT4T-2OD:PC₇₁BM system, the PCE can be improved from 4.26% (without CBL) to 9.02% after inserting the Ba(OH)₂ buffer layer. More importantly, the Ba(OH)₂ buffer layer presents similar positive effects in the conventional and inverted all-polymer devices based on a new combination, i.e., the PBDT-TS1:N2200 system. The dramatic enhancement in device performance resulted from the suitable work function of Ba(OH)₂, extremely high transmittance, and excellent film-forming capability. Therefore, inserting Ba(OH)₂ as the CBL is a simple, low-cost, and widely applicable method to simultaneously improve the conventional and inverted photovoltaic device performance.