UV Photodetectors Based on BiOCl Nanosheet Arrays: The Effects of Morphologies and Electrode Configurations

Abstract

A facile chemical bath method is adopted to grow bismuth oxychloride (BiOCl) nanosheet arrays on a piece of Cu foil (denoted as BiOCl-Cu) and isolated BiOCl nanosheets are collected by ultrasonication. A self-supporting BiOCl film is obtained by the removal of Cu foil. Photodetectors (PDs) based on these BiOCl materials are assembled and the effects of morphologies and electrode configurations on the photoelectric performance of these PDs are examined. The BiOCl nanosheet PD achieves high responsivities in the spectral range from 250 to 350 nm, while it presents quite a small photocurrent and slow response speed. The BiOCl film PD yields low photocurrents and near-unity on-off ratios, demonstrating poor photoelectric performance. The photocurrent of the BiOCl-Cu PD with both electrodes on the BiOCl film is much higher than those of these above-mentioned PDs, and the response times are fast. Meanwhile, the BiOCl-Cu PD with separate electrodes on the BiOCl film and Cu foil achieves even higher photocurrents and presents a self-powering characteristic, depicting the improved photodetecting performances induced by the specific morphology and distinct electrode configuration. These results would promote the applications of BiOCl nanostructures in the photoelectric devices.

Atomically Thin Oxyhalide Solar‐Blind Photodetectors

“…Interestingly, the BiOCl photodetector also has a clear response to solar‐blind UV light (200–250 nm) and yellow light (600 nm), which may be derived from the defect level, such as oxygen vacancy. [ 19 ] The local states caused by the defect level can broaden the light response to solar‐blind UV and visible range, and effectively capture the charge carrier. [ 28,31 ] Responsivity ( R ) and specific detectivity ( D *) are two important parameters for evaluating the sensitivity of photodetectors.…”

Recent Progress of Heterojunction Ultraviolet Photodetectors: Materials, Integrations, and Applications

“…Depending on diverse preparation methods, the bandgap of BiOCl varies from 3.0 to 3.5 eV, which makes BiOCl nanostructures suitable for UV‐A light detection 51. However, these BiOCl‐based UV photodetectors suffer from poor conductivity and low photoresponse 52. More efforts should be paid to overcome these deficiencies.…”

Enhancing the Photoelectric Performance of Photodetectors Based on Metal Oxide Semiconductors by Charge‐Carrier Engineering

“…Forced by the applied bias, the depletion of the charge carriers out of the junctions is reduced, which leads to increased photocurrent and shortened response times. However, the further increase of applied voltage will increase the short noise and lead to increased dark current and power consumption . Thus, it is necessary to choose an appropriate operation voltage to make a balance between high performance and facile power supply in practical application.…”

“…Excluding the influences from the surface states of semiconductors, the adoption of two metal electrodes with large difference in work functions causes asymmetric metal contacts and a built‐in potential, endowing Schottky diodes with rectifying and self‐powering characteristics. Ouyang et al grew bismuth oxychloride (BiOCl) nanosheet arrays on a piece of Cu foil (denoted as BiOCl–Cu) and fabricated the BiOCl–Cu samples into BiOCl–Cu‐1 and BiOCl–Cu‐2 PDs by adopting different electrode configurations . Under 350 nm light illumination at 5 V, the BiOCl–Cu‐1 PD with both Ag electrodes on the BiOCl film yields a relatively high photocurrent of 353 pA, the rise/decay times are calculated to be 0.56/0.59 s. Moreover, a higher photocurrent of 1040 pA is achieved by the BiOCl–Cu‐2 PD with one Ag electrode on the BiOCl film and the Cu foil substrate as the other electrode, while the response speed remains nearly the same.…”