Doping and Design of Flexible Transparent Electrodes for High-Performance Flexible Organic Solar Cells: Recent Advances and Perspectives

Substantial effort has been devoted to both chemical doping and design of flexible transparent electrodes (FTEs) for flexible organic solar cells (OSCs) in the past decade. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), graphene, metal nanostructures, metal oxide/ultrathin metal/metal oxide, Mxene, and their hybrid electrodes emerge to be the most promising flexible conducting materials over indium tin oxide. The FTE fabrications play a critical role in flexible OSCs. This feature review article summarizes the current status on the researches of the FTEs including various approaches and strategies to boost the conductivity, work function, mechanical flexibility, wettability, etc, which directly affect the performances of the flexible OSCs. The most cutting edge progresses on both FTEs and flexible OSCs are highlighted along the line. Advantages and plausible issues are pointed out. Perspectives are provided that can advance the developments of the flexible OSCs. This review raises the awareness for the importance of developing plenty of FTEs and reveals their critical role in flexible OSCs.