Enhanced power conversion efficiency of polymer solar cells through the use of 4-fluorobenzonitrile as an additive

In this work, 4-fluorobenzonitrile (4-FBN) was introduced as a new additive compound into the photoactive layer of a polymer solar cell (PSC) based on a poly(3-hexylthiophene):[6,6]-phenyl-C ₆₁- butyric acid methyl ester (P3HT:PCBM) blend system. The incorporation of 4-FBN allowed both increased light absorption (φ-φ* transition efficiency) in the visible region and enhanced X-ray diffraction peak of (100), which is attributed to the enhanced crystallinity of the P3HT chains, leading to a higher short-circuit current (J _sc) and fill factor (FF). Thus, the overall efficiency of the annealed PSCs was considerably improved from 3.57% (without 4-FBN) to 4.41% (with 4-FBN).