An Easily Accessible Cathode Buffer Layer for Achieving Multiple High Performance Polymer Photovoltaic Cells

摘要

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/cm(2). 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.