Pyrrolo[3,4-c]pyrrole-1,3-dione-based large band gap polymers containing benzodithiophene derivatives for highly efficient simple structured polymer solar cells

Abstract

Pyrrolo[3,4‐c]pyrrole‐1,3(2H,5H)‐dione (DPPD)‐based large band gap polymers, P(BDT‐TDPPDT) and P(BDTT‐TDPPDT), are prepared by copolymerizing electron‐rich 4,8‐bis(2‐ethylhexyloxy)benzo[1,2‐b:4,5‐b′]dithiophene (BDT) or 4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene (BDTT) unit with novel electron deficient 2,5‐dioctyl‐4,6‐di(thiophen‐2‐yl)pyrrolo[3,4‐c]pyrrole‐1,3(2H,5H)‐dione (TDPPDT) unit. The absorption bands of polymers P(BDT‐TDPPDT) and P(BDTT‐TDPPDT) cover the region from 300 to 600 nm with an optical band gap of 2.11 eV and 2.04 eV, respectively. The electrochemical study illustrates that the highest occupied/lowest unoccupied molecular orbital energy levels of P(BDT‐TDPPDT) and P(BDTT‐TDPPDT) are −5.39 eV/−3.28 eV and −5.44 eV/−3.40 eV, respectively. The single layer polymer solar cell (PSC) fabricated with a device structure of ITO/PEDOT:PSS/P(BDT‐TDPPDT) or P(BDTT‐TDPPDT):PC70BM+DIO/Al offers a maximum power conversion efficiency (PCE) of 6.74% and 6.57%, respectively. The high photovoltaic parameters such as fill factor (∼72%), open circuit voltage (Vₒc, ∼0.90 V), incident photon to collected electron efficiency (∼76%), and PCE obtained for the PSCs made from polymers P(BDT‐TDPPDT) and P(BDTT‐TDPPDT) make them as promising large band gap polymeric candidates for PSC application. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3564–3574