A B S T R A C TLateral bulk heterojunctions (LBHJ) provide a tool to directly probe the active area of photovoltaic devices using microscopy techniques. Here, we use scanning photocurrent microscopy (SPCM) to probe an organic photovoltaic (OPV) device with poly [{4,8-bis[(2-ethylhexyl)(PTB7):[6,6] phenyl-C61-butyric acid methyl ester (PC 61 BM). The effects of the additive 1,8-diiodooctane (DIO) on the recombination dynamics and morphology are probed in real space in a LBHJ structure. By using SPCM, we can see a larger increase in the space charge region for samples with DIO when compared to those without DIO. This indicates that the additive improves film morphology leading to increased charge extraction efficiency and decreased recombination.