We report the synthesis, characterization, and implementation of various naphtho[2,3- b:6,7-b’]dithiophene (
NDT)-based donor molecules for organic photovoltaics (OPVs) When NDT(TDPP)2( TDPP= thiophene-capped diketopyrrolopyrrole) contains all branched 2- ethylhexyl chains and is combined with the electron acceptor PC61BM, a power conversion efficiency (PCE) of 4.06±0.6% is achieved. This respectable PCE is attributed to the broad, high oscillator strength visible absorption, the ordered molecular packing, and a high hole mobility of 0.04 cm2·V-1·s-1. We find utilizing linear C-12 side chains on either the TDPPor NDTframework dramatically increases the d-spacing, which directly correlates with inferior OPV device performance. This leads to the conclusion that the selection of an appropriate side chain plays a key role in determining OPV device performance of a small molecule donor.