A solution-processable dibromoindigo with an alkyoxyphenyl solubilizing group is developed and used as a new electron acceptor in organic photodiodes. The solution-processed fullerene-free organic photodiodes show an almost spectrally flat response with a high responsivity (0.4 A W-1) and a high detectivity (1 x 10(12) Jones). These values are comparable to silicon-based photodiodes.