Simple perylene diimide based polymer acceptor with tuned aggregation for efficient all-polymer solar cells

Polymer acceptors for organic solar cells have got increased attention and becoming a strong candidate to replace small molecular electron acceptors. Here, a polymer acceptor (PBDTβNPDI) was constructed with naphthyl substituted asymmetric benzo [1,2-b:4,5-b']dithiophene (BDTβN) as donor unit and simple N,N′-Bis(1-propylbutyl)-1,7-dibromoperylene-3,4:9,10-tetracarbox- diimide (PDI) as acceptor unit. The designed polymer has broad absorption spectrum and tuned aggregation with asymmetric donor unit. Then all-polymer solar cells based on PTBTz-2 electron donor and PBDTβNPDI electron acceptor were prepared. The results exhibit that the device has matched energy levels, complementary absorption spectra, and desirable crystallites and nanoscale phase separation, which result in balanced mobility, low weak bimolecular recombination, and thus obtain a remarkable power conversion efficiency of 6.14% with high short circuit current density of 13.89 mA cm−2 and decent open circuit voltage of 0.88 V. The results indicate that rational regulation of PDI polymers by asymmetric strategies can obtain ideal polymer accepters, and it has a strong potential to get better results with our in-depth research.