Main content area

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.