High Stability of Broadband Photomultiplier Organic Photodetector with metal ion-chelated polymer as an electron tunneling injection dipole layer

Broadband photomultiplier organic photodetectors (PM-OPDs) have tremendous potential for use in a variety of photoimaging, physical health monitoring, and wearable applications. However, the interfacial mismatch between electrodes and organic semiconductors inhibits the long-term working stability and reliability of devices. Here, we devised high-performance and stability PM-OPDs by using Zn2+-chelated ethoxylated-polyethylenimine (denoted as PEIE-Zn) as an electron tunneling injection dipole layer between ITO and P3HT:PC71BM: Y6 (3:20:80) broadband photoactive layer. The specific detectivity of the PEIE-Zn-modified PM-OPDs was higher than 1012 Jones in the whole spectral response range (350-1000 nm) under 10V bias. The external quantum efficiency of the device exceeded 1000 % in the whole spectral response range under -20V bias. The transient photoresponse curve of the device has no obvious peaks and fluctuations, and the photocurrent density drops only 2.34 % and 0.25 % at 10 V and -20 V bias after illumination, respectively. The device exhibited very good stability over the course of a week, with its photocurrent density maintained at more than 98.94 % of the initial photocurrent density in the ambient environment without encapsulation. This work improves interface contact by modifying the ITO electrode with PEIE-Zn, providing a practical design solution for devices with high response and stability for broadband PM-OPDs.