In Operando Visualization of Interfacial Band Bending in Photomultiplying Organic Photodetectors

Charge injection is a basic transport process that strongly affects performance of optoelectronic devices such as light-emitting diodes and photodetectors. In these devices, the charge injection barrier is related to the band bending at the active layer/electrode interface and exhibits sophisticated dependence on interface structure and device operating conditions, making it difficult to determine via either theoretical prediction or experimental measurements. Here, in operando cross-sectional scanning Kelvin probe microscopy (SKPM) has been applied in organic photo- detectors to visualize the interfacial band bending. The photo-induced interfacial band bending becomes more significant with increasing reverse bias voltage, resulting in reduced charge injection barrier and facilitated charge injection. The photoinduced injection current is orders of magnitude higher than the photocurrent directly generated from light absorption and thus leads to significant photomultiplication. Furthermore, the interfacial structure is tuned to further enhance photoinduced interfacial band bending and the photomultiplication factor.

Automated summary

Charge injection is a crucial transport process that impacts the performance of optoelectronic devices. In this study, scanning Kelvin probe microscopy was used to visualize the interfacial band bending in organic photodetectors, revealing a significant enhancement in the photomultiplication factor due to photoinduced interfacial band bending.