N-Annulated perylene diimide derivatives as non-fullerene acceptors for solution-processed solar cells with an open-circuit voltage of up to 1.14 V

Three different non-fullerene small molecular acceptors containing N-annulated perylene diimide, named di-PNR, TPA-PNR and EDOT-PNR, were successfully designed and synthesized for photovoltaic applications. Introducing an electron donating unit such as triphenylamine (TPA) or 2,3-dihydrothieno[3,4-b][1,4]dioxine (EDOT) into the N-annulated PDI derivatives significantly influences the light-harvesting capabilities, energy level, morphology as well as the photovoltaic performance. Preliminarily, TPA-PNR and EDOT-PNR possessed lower band gaps and higher HOMO/LUMO energy levels. Power conversion efficiencies (PCEs) of 5.29% and 4.54% were obtained for the inverted solar cells based on the blends of PTB7-Th/di-PNR and PTB7-Th/TPA-PNR, respectively, resulting from the smooth morphology of the blend films and the intense light absorption that increases the J(sc) and FF. Under the same optimization conditions, EDOT-PNR exhibited a low PCE of 1.6% with a remarkably high V-oc of 1.14 V because of its higher LUMO energy level, which was one of the highest V-oc values reported for organic solar cells using N-annulated PDI derivatives as electron acceptors. Our work offers effective guidelines for the design of non-fullerene acceptors using N-annulated PDI derivatives.