Response of biophotonic device using retinoid

The authors focus on the retina in the human eye and consider retinoic acid to be the most appropriate for use in photoreceptive devices. The authors fabricated retinoic acid–chitosan film by using the layer-by-layer self-assembly process. The photocurrent value of the devices increased from 4·0 to 7·0 mA when used in optimized conditions. One of the best responses of these manually fabricated photoreceptive devices was that the photocurrent was 7 mA and the photocurrent response continued during the longest period to date of 9 h, which is an 81 times longer life time than before. The authors calculated the external quantum efficiency of the photocurrent response for devices with the best performance. The estimated external quantum efficiency of the photocurrent response for the best device was 4·53. In comparison, for one of the gel-type devices, the efficiency was 0·004. The mechanism of the photocurrent response of biophotonic devices seems to be the radical reaction rather than any ionic or charged carrier reaction.