Ultrathin anode buffer layer for enhancing performance of polymer solar cells

A series of polymer solar cells (PSCs) based on poly[(4,8-bis-(2- ethylhexyloxy)-benzo[1,2-b:4,5-b′(dithiophene)-2,6-diyl-alt-(4-(2- ethylhexanoyl)-thieno[3,4-b]thiophene)-2,6-diyl] (PBDTTT-C) and [6,6]phenyl-C71-butyric acid methyl ester (PC₇₁BM) were fabricated with various anode buffer layers. The power conversion efficiency (PCE) of PSCs was improved to 4.91% for the cells with PEDOT:PSS/LiF (1 nm) as anode buffer layer, which corresponds to 26.2% efficiency improvement compared with the cells with PEDOT:PSS as anode buffer layer. The PSCs with PEDOT:PSS/LiF as anode buffer layer show a maximum short-circuit density (Jsc) of 13.70 mA/cm ², with open circuit voltage (Voc) of 0.73 V and fill factor (FF) of 49.1% under illumination 100 mW/cm² AM 1.5 G simulated solar light. The dominant mechanism for the performance improvement of PSCs could be attributed to the increased charge carrier collection ability by anode buffer layers.