Roles of electrode interface on the performance of organic photodetectors

- Roles of electrode interface on the performance of organic based photodetectors are investigated.
- Detectivity of the organic photodetectors is dramatically enhanced up to a highest one of 1.25 × 1013 Jones at −0.1 V by interfacial modification of the cathode electrode.
- Response speed is also largely increased with modification of the electrode interface, and the devices show a shortest response time of few microseconds.

We report that the performance of organic photodetectors (OPDs) is significantly enhanced by tuning of electrode interface. Amino acids, PEO or LiF were deposited onto indium tin oxide (ITO) via a solution process (spin-coating or a hydrothermal process). These OPDs with the modified ITO as a cathode exhibit a large enhancement of the detectivity which is up to one order of magnitude higher than that of the counterpart OPDs with the pure ITO cathode. Meanwhile, the OPDs with the modification of ITO have the best response speed with a rise time of 3.9 μs, which is half shorter than that (7.8 μs) of the compared OPDs with pure ITO. The enhancement of the response speed was attributed to a better ohmic contact of the ITO electrode with the active layer due to the reduced work function of the ITO after modification. Impedence measurements show that the OPDs with the ITO modification have a largely decreased series resistance (Rs), which plays an important role in the increase of the performance.