The search for novel solar cell designs as an alternative to standard silicon solar cells is important for the future of renewable energy production. One such alternative design is the carbon nanotube/silicon (CNT/Si) heterojunction solar device. In order to improve the performance of large area CNT/Si heterojunction solar cells, a novel organic material, 4,10-bis(bis(4-methoxyphenyl)amino)naptho[7,8,1,2,3-nopqr]tetraphene-6,12-dione (DPA-ANT-DPA (shortened to DAD)), was added as an interlayer between the CNT film and the silicon surface. The interlayer was examined with SEM and AFM imaging to determine an optimal thickness for solar cell performance. The DAD was shown to improve the device performance with the efficiency of large area devices improving from 2.89% ± 0.40% to 3.34% ± 0.10%.