By employing mixed solvents of chlorobenzene (CB) and 1,2-dichlorobenzene (DCB) atoptimized ratios, the aggregation and miscibility of the polymerblends can be finely controlled to reduce domain size andachieve favorable morphology which finally leads to balancedand increased hole and electron mobilities. A PCE of 4.8% wasachieved for PSEHTT/PNDIS-HD-based OSCs. The same groupalso developed a series of novel NDI–selenophene (PNDIS-xBO)through random copolymerization of two NDI units with 2-butyloctyl (BO) and 2-decyltetradecyl (DT) side chains, whichimproved the interpenetrating network and molecular packingstructure, thus the crystallinity and electron mobility of the polymers [91]. PNDIS-30BO (P16) (Fig. 6), with 30 mol% of BO alkylside chain composition-based devices exhibited the best photovoltaic performance with 4.4% PCE and 10.4 mA cm2 photocurrent compared with others.