Small‐Molecule Solar Cells with Fill Factors up to 0.75 via a Layer‐by‐Layer Solution Process

An oligothiophene-based molecule (BDT-3T-CA) using a molecular engineering approach is applied to solution-processed layer-by-layer solar cells. The solar cells based on BDT-3T-CA/PC61BM (a fullerene derivative) exhibit power conversion efficiency (PCE) values as high as 4.16% and fill factor (FF) values up to 0.75. The FF of 0.75 is the highest value reported for solution processed small molecule solar cells.