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