Self‐Powered and Broadband Photodetector Based on SnS₂/ZnO_1−xS_x Heterojunction

Abstract

is constructed by utilizing an integrated nanosystem consisting of an energy harvesting or storage unit and a light sensor. The simplified structure and maintenancefree features of the first category endow the low-cost advantage as compared with the second one. Furthermore, the heterojunction-based PDs generally possess superior performance compared with PEC and the integrated nanosystem. [10,11] In addition, the vertical heterojunction configuration is considered as one of the most essential cornerstones of high performance optoelectronic devices, which is attributed to its strong built-in electric field, the short carrier diffusion path, and the large active area. [12] Although considerable efforts have been devoted, [13-18] the reports on selfpowered broadband PDs remain limited and several challenges are to be solved. For instance, various photoactive materials and methods are applied to construct PDs, but it is still challenging to design a high performance self-powered PDs based on earth abundant materials by a facile method. In addition, several conditions need to be met for the photoactive materials: the large absorption coefficient, the superior carrier mobility, the tunable energy-level alignment with electrode for the sake of high-performance PDs. [5] Thus, it is still demanding to find suitable photoactive materials for PDs that can work at room temperature in the range from UV to NIR. Metal chalcogenides semiconductors are promising candidates for photoelectric devices owing to their specific electronic and optoelectronic properties. [19,20] Tin disulfide (SnS 2) is an indirect bandgap (2.2 eV) semiconductor, which has drawn considerable attentions owing to its advantages of low cost, earth abundance, nontoxicity, and environmental friendliness. [21] The absorption coefficient and carrier mobility is up to 10 5-10 6 cm −1 and 230 cm 2 V −1 s −1 , respectively. [5,22] SnS 2based PDs have shown superior performance, such as high on/off ratio, high responsivity, good stability, and fast response speed. [22-25] In addition, it has been proved that SnS 2 can be applied to construct a PD in the range from UV to NIR light, although it need to be powered externally. [26] Zinc oxide (ZnO), a typical n-type wide bandgap semiconductor, has already been widely applied in optoelectronic devices due to its wide bandgap and high exciton biding energy. [27-29] In addition, ZnO-based PDs are endowed the advantages of low applied field, fast response, and no oxygen dependency. [30,31] On the other hand, the doping of S atom can not only improve the optical and electrical properties of ZnO, but also modify the band structure of Self-powered photodetectors that can work without an external power source are expected to play a crucial role in future optoelectronic devices. Herein, SnS 2 /ZnO 1−x S x heterojunctions are fabricated by a facile sputtering method and constructed as self-powered broadband photodetectors covering from UV (365 nm) to NIR (850 nm). The self-powered device shows a superior responsivity of 8.28 mAW...

Self‐Powered Broad Spectral Photodetector with Ultrahigh Responsivity and Fast Response Based on Sb2Se3/VO2 Heterojunction

“…Achieved by traditional photovoltaic effect by means of Schottky junctions, p–n junctions, and heterojunctions, self‐powered photodetectors, which can operate without outer power source, have attracted increasing attention recently. [ 9 ] With the advantages of light weight, self‐sufficient, and good long‐term properties, self‐powered photodetectors show great potential in many aspects, such as functional nanosystems, [ 10 ] light‐wave communications, [ 11 ] wire‐free route for artificial vision, [ 12 ] and long‐term unattended wastewater and air‐pollution monitoring. [ 13 ] However, despite the advantages of being without outer energy, most self‐powered photodetectors suffer from low photoresponsivity, hindering their commercial applications.…”

Recent Progress of Methods to Enhance Photovoltaic Effect for Self‐Powered Heterojunction Photodetectors and Their Applications in Inorganic Low‐Dimensional Structures

“…[ 123 ] By a facile sputtering method, type II band alignment of SnS 2 /ZnO 1− x S x self‐powered PD shows a photodetectivity of 5.09 × 10 10 Jones, a high I on / I off ratio of 1.08 × 10 5 at 365 nm, and a fast response speed with a rise time of 49.51 ms and a decay time of 25.93 ms (Figure 9e). [ 25 ] The coupling mechanism of piezo‐phototronic effect and ferroelectric polarization in the La‐doped bismuth ferrite film (BLFO)/n‐type zinc oxide (ZnO) nanowire heterojunction, makes the performance of the PD obviously enhanced under 405 nm laser illumination. [ 39 ]…”

“…Reproduced with permission. [ 25 ] Copyright 2020, Wiley‐VCH. f) The GaN:layered rGO hybrid heterojunction.…”

“…Depending on the charge separation features of the interface, this PD type can be further divided into three types: p–n junction PDs, Schottky junction PDs, and photoelectrochemical (PEC) PDs. [ 25 ] The second category is designed to utilize an integrated nanosystem, which consists of an energy harvesting or storage unit and a light sensor. By comparison, the maintenance‐free and simplified structure of the first category is less expensive and self‐powered PEC PDs usually operate in a liquid medium, which seriously limits the scope of their applications.…”

CdS nanobelt-based self-powered flexible photodetectors with high photosensitivity

“…The second is designed with integrated nanosystems that include an energy harvesting or storage unit as well as a light sensor. 11 . The maintenance free features and simplified structure of the first category has a low-cost advantage over the second one.…”