Photoactive devices include an active region disposed between first and second electrodes and configured to absorb radiation and generate a voltage between the electrodes. The active region includes an active layer comprising a semiconductor material exhibiting a relatively low bandgap. The active layer has a front surface through which radiation enters the active layer and a relatively rougher back surface on an opposing side of the active layer. Methods of fabricating photoactive devices include the formation of such an active region and electrodes.