Efficient all polymer solar cells employing donor polymer based on benzo[1,2-b:4,5-b']dithiophene unit

Abstract

We reported all polymer solar cells (all-PSCs) employing BDT-based donor-acceptor (D-A) polymers composed of benzo[1,2-b:4,5-b']dithiophene (BDT) and thiadiazolo[3,4-c]pyridine (PyTZ) (PBPT-8 and PBPT-12) as donor and NDI-based n-type polymer Poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) (N2200) as acceptor. The influence of thermal annealing on the performance of all-PSCs was systematically investigated and discussed. It was found that the pre-annealing of the active blend films could significantly improve the all-PSCs performance. Both PBPT-8/PBPT-12:N2200 systems can deliver promising PCEs (4.12% and 4.25%) at the optimal annealing temperature of 160 oC due to the promoted film quality and charge transport properties. Morphology investigation and carrier mobility measurements have been carried out to analyze the effect of thermal annealing. This study suggests that BDT-based polymer:N2200 systems can be promising candidates for all-PSCs, with thermal annealing as an effective approach to promote the device performance.