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 PC 61BM, 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 cm 2·V -1· s-1. We find utilizing linear C-12 side chains on either the TDPP or NDT framework 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.