Overall Enhanced Performance of Polymer Photodetectors by Co‐Modifying ITO with PEIE and ZnO

Abstract

Recently, ZnO and polyethyleneimine ethoxylated (PEIE) have been, respectively, applied to modify ITO to achieve the polymer photodetectors (PPDs) with a similar high detectivity of 1012 Jones. The ZnO device shows a lower dark current due to the surface defect states of ZnO, while the PEIE device exhibits a higher photocurrent because of the formed PEIE dipole layer on ITO. Therefore, the former has a higher linear dynamic range (LDR) of about 100 dB and a lower external quantum efficiency (EQE) of 200%, while the latter has a higher EQE of about 2000% and a lower LDR of 60 dB. This work demonstrates a strategy of combing the advantages of both devices using PEIE and ZnO co‐modified ITO. The resulting device exhibits an increased photocurrent and a reduced dark current, leading to overall enhanced performances with EQE of 1703%, responsivity of 7.55 A W−1, detectivity of 4.88 × 1013 Jones, and LDR of 117 dB under −0.3 V. The key of the co‐modification is that PEIE must directly modify ITO to form the electrical dipole layer and ZnO needs to be in contact with the active layer so that the surface defects can act as carrier trapping centers.