Nonfullerene Polymer Solar Cells based on a Perylene Monoimide Acceptor with a High Open-Circuit Voltage of 1.3 V

Nonfullerene polymer solar cells (PSCs) are fabricated with a perylene monoimide-based n-type wide-bandgap organic semiconductor PMI-F-PMI as an acceptor and a bithienyl-benzodithiophene-based wide-bandgap copolymer PTZ1 as a donor. The PSCs based on PTZ1:PMI-F-PMI (2:1, w/w) with the treatment of a mixed solvent additive of 0.5% N-methyl pyrrolidone and 0.5% diphenyl ether demonstrate a very high open-circuit voltage (V-oc) of 1.3 V with a higher power conversion efficiency (PCE) of 6%. The high V-oc of the PSCs is a result of the high-lying lowest unoccupied molecular orbital (LUMO) of -3.42 eV of the PMI-F-PMI acceptor and the low-lying highest occupied molecular orbital (HOMO) of -5.31 eV of the polymer donor. Very interestingly, the exciton dissociation efficiency in the active layer is quite high, even though the LUMO and HOMO energy differences between the donor and acceptor materials are as small as approximate to 0.08 and 0.19 eV, respectively. The PCE of 6% is the highest for the PSCs with a V-oc as high as 1.3 V. The results indicate that the active layer based on PTZ1/PMI-F-PMI can be used as the front layer in tandem PSCs for achieving high V-oc over 2 V.