Self‐Powered Si/CdS Flexible Photodetector with Broadband Response from 325 to 1550 nm Based on Pyro‐phototronic Effect: An Approach for Photosensing below Bandgap Energy

Abstract

Cadmium sulfide (CdS) has received widespread attention as the building block of optoelectronic devices due to its extraordinary optoelectronic properties, low work function, and excellent thermal and chemical stability. Here, a self-powered flexible photodetector (PD) based on p-Si/n-CdS nanowires heterostructure is fabricated. By introducing the pyro-phototronic effect derived from wurtzite structured CdS, the self-powered PD shows a broadband response range, even beyond the bandgap limitation, from UV (325 nm) to near infrared (1550 nm) under zero bias with fast response speed. The light-induced pyroelectric potential is utilized to modulate the optoelectronic processes and thus improve the photoresponse performance. Lasers with different wavelengths have different effects on the self-powered PDs and corresponding working mechanisms are carefully investigated. Upon 325 nm laser illumination, the rise time and fall time of the self-powered PD are 245 and 277 µs, respectively, which are faster than those of most previously reported CdS-based nanostructure PDs. Meanwhile, the photoresponsivity R and specific detectivity D* regarding to the relative peak-to-peak current are both enhanced by 67.8 times, compared with those only based on the photovoltaic effect-induced photocurrent. The self-powered flexible PD with fast speed, stable, and broadband response is expected to have extensive applications in various environments.

Low‐dimensional nanomaterial/Si heterostructure‐based photodetectors

“…The key step in fabricating the flexible Si substrate was etching Si wafers with 50% potassium hydrate solution at 130 °C for several hours. Wurtzite ZnO or CdS have been integrated with the flexible Si substrate, where the pyroelectric‐polarization potential produced within nanowires coupled with the inner electric field of the p‐n junction performs very well. Both the photoresponsivity and detectivity with respect to the relative peak‐to‐peak current were improved.…”

“…Copyright 2018, Elsevier. F, Schematic diagram of the self‐powered device . Copyright 2018, Wiley‐VCH.…”

“…F, Schematic diagram of the self-powered device. 127 Copyright 2018, Wiley-VCH. PEDOT:PSS, poly (3,4-ethylenedioxythiophene) polystyrene sulfonate Si remained.…”

“…Recently, a self-driven flexible photodetector based on p-Si/n-CdS heterojunction ( Figure 11F) was prepared through a simple hydrothermal synthesis method by Wang and coworkers. 127 The photodetector had a wide spectral response range in the UV (325 nm) to NIR region (1550 nm). The photoresponse range even exceeded the intrinsic bandgaps of Si and CdS.…”

Narrow‐Band QD‐Enhanced PIN Metal‐Oxide Heterostructure Phototransistor with the Assistance of Printing Processes

“…In‐depth studies on heterostructure photodetectors are of particular interest because this approach can boost the optoelectric conversion efficiency . In particular, the QD‐based PIN structure detector with both electron and hole blockers show low dark current, sensitive light absorption and high detectivity due to its enhanced structure .…”