• additives;
  • phase separation;
  • 1, 8-diiodooctane;
  • polymer solar cells


Thumbnail image of graphical abstract

An alternating copolymer (PBDTC10DBT) of benzo[1,2-b:3,4-b′]dithiophene (BDT) as donor and 4,7-di(3-decylthiophen-2-yl)-2,1,3-benzothiadiazole (C10DBT) as acceptor is designed and synthesized. In order to investigate the effect of the 1,8-diiodooctane (DIO) additive on the morphology and photovoltaic performance, polymer solar cells (PSCs) based on PBDTC10DBT:[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) are fabricated. The morphology of blend films and the interpenetrating network between the donor and the acceptor is examined using atomic force microscopy and scanning electron microscopy. This work shows that the PBDTC10DBT:PC61BM blend films with added DIO (3%, v/v) have improved absorption and controlled phase separation. Morphology with a domain size of 20–30 nm that forms in the DIO system is proposed to facilitate charge transport and minimize charge carrier recombination, which are the main reasons why the power conversion efficiency of the PSCs is improved from 1.93% (without DIO) to 2.23% (with DIO).