In situ integration of squaraine-nanowire-array-based Schottky-type photodetectors with enhanced switching performance.

Organic nanostructure-based photodetectors are important building blocks for future high-performance, low-cost, flexible nano-optoelectronic devices. However, device integration remains a large challenge, and the structure-dependent performance of the device has been seldom studied. Here, we report the in situ integration of 2,4-bis[4-(N,N-dimethylamino)phenyl]squaraine (SQ)-nanowire (NW)-array-based photodetectors by growing the organic NW arrays on prefabricated electrodes through an evaporation-induced self-assembly process. In contrast with ohmic-contact devices, asymmetric electrode pairs of Au-Ti were utilized to achieve the construction of Schottky-type photodetectors on the basis of organic NW arrays. Significantly, the Schottky-type photodetectors exhibited a significantly enhanced performance as compared to the ohmic-type devices in terms of their higher photosensitivity and switching speed. The presence of a strong built-in electric field at the junction interface, which greatly facilitated the separation/transportation of photogenerated electron-hole pairs, was suggested to be responsible for the superior performance of the Schottky-type photodetectors. More importantly, the organic NW-array-based devices also showed a higher sensitivity and reproducibility than that of the single NW-based devices, and they were capable of low-light detection. The investigation of the photodetector circuitry also disclosed a very low pixel-to-pixel variation owing to the average effect of the NW-array-based devices. It is expected that organic NW-array-based Schottky-type photodetectors will have important applications in future organic nano-optoelectronic devices.