Metallic and Low-Work-Function PEDOT:PSS Cathodes for Flexible Organic Solar Cells Exhibiting Over 15% Efficiency and High Stability

Flexible organic solar cells (OSCs) with an inverted structure have the advantage of high stability against ambient air over normal flexible OSCs. However, inverted flexible OSCs with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) transparent electrodes and PM6:Y6 active layers have suffered from a limited power conversion efficiency (PCE) of no higher than 13.6% to date. Herein, we developed a simple room-temperature crystallization technology of PEDOT:PSS cathodes and then reported an inverted flexible OSC of the cathodes and PM6:Y6 of over 15% PCE. This PCE is the best result among the inverted flexible OSCs with the polymeric electrodes and PM6:Y6. The high PCE is attributed to the superior conductivity and low work function of the cathodes, which are beneficial for efficient electron transport and collections in the flexible devices. Moreover, the flexible OSCs maintained 93.2% and 82.7% of the initial PCE when exposed to nitrogen and ambient air for 45 days, respectively.