All-organic arrayed photodetectors with fast UVA–UVC response based on self-aligned planar BPEA nanowires

Abstract

Single-crystalline 9,10-bis(phenylethynyl)anthracene (BPEA) nanowires are promising building blocks for all-organic ultraviolet (UV) photodetectors owing to their environmental stability and efficient absorption of UV radiation. However, many of the intrinsic properties of BPEA nanowires become largely smeared when they adopt disordered ensembles. In this study, by exploiting the exceptional graphoepitaxial effect of hydrophobic parallel nanogrooves, self-aligned planar BPEA nanowires with high crystallinity and chemical purity are grown over the entire sapphire surface. They are then integrated in situ to form arrayed photodetectors by direct deposition of metal electrodes. This strategy helps preserve the exceptional properties of single-crystalline BPEA nanowires to improve photoresponse performance, as unwanted structural damage and chemical impurities associated with the demanding post-growth transfer and alignment steps can be eliminated. Under ambient conditions, these photodetectors exhibit fast and sensitive photoresponse to UV radiation in the 200–400 nm range, covering the short-wave UV (UVC), the middle-wave UV (UVB), and the long-wave UV (UVA) bands. The arrayed photodetectors also enable statistical testing and evaluation of their performance, a prerequisite for advancing nanowire devices into real-world applications. Averaging over 81 detectors gives a responsivity of 0.30 A/W, a detectivity of 3.11 × 109 Jones, and a response time of 31.0 ms under 380 nm light at 20.32 mW/cm2 and 20-V bias. The proposed methods for the rational growth of aligned nanowires and scaled-up production of photodetectors represent a substantial advance toward the implementation of UV photodetectors from organic molecules.