Efficient UV Photodetectors Research Articles

Narrowing band gap and enhanced optoelectronic properties in methylammonium lead chloride perovskite under pressure

In this study, we explore the impact of hydrostatic pressure on the structural stability, elastic properties, mechanical behavior, thermodynamics, and optoelectronic characteristics of lead halide perovskite, specifically focusing on CH3NH3PbCl3. Through high-level ab initio simulation techniques, we investigate the lattice squeezing effects on this methylammonium lead chloride perovskite. Our findings reveal that applying hydrostatic pressure squeezes lattice parameters, influences the electronic profile, and results in spin-split band edges. The band gaps in compressed perovskites are observed to be narrower, with the potential for pressure-induced closures, offering new electronic features under various thermodynamic conditions. Because of the high-quality crystal and its optimal optical band gap, we successfully construct an efficient UV-photodetector, highlighting its promising applications in optoelectronics. This work contributes to a deeper atomistic understanding of inorganic halide perovskite behavior under external pressure and demonstrates the potential for realizing enhanced electronic functionalities through pressure conditions.

Nitrogen-doped carbon quantum dots decorated ZnO nanorods array film for efficient UV photodetector applications

Nitrogen-doped carbon quantum dots decorated ZnO nanorods array film for efficient UV photodetector applications

Ultrasensitive self-powered heterojunction ultraviolet photodetector of p-GaN nanowires on Si by halide chemical vapour deposition

In this study, we report the fabrication of quasi-aligned p-GaN nanowires (NWs) on n-Si (1 1 1) substrate by halide chemical vapour deposition (HCVD) using MgCl2 precursor and followed by low-energy electron beam irradiation to activate the Mg acceptor doping in GaN NWs. We aimed to attain a comprehensive understanding of p-doping in GaN NWs growth, extensive characterizations and fabrication of UV photodetector (PDs) based on p-GaN NWs/n-Si heterojunction. To realize the efficient UV photodetectors, we measure the current–voltage (I–V) characteristics of heterojunction PDs under dark and illuminated conditions and the I–V curve demonstrates good rectifying behaviours with 0.2 V turn-on voltage. At zero bias, the heterojunction PDs show a reverse photocurrent of 1.27 × 10−6 A with a very low dark current of 2.35 × 10−9 A under 325 nm UV illumination. Besides, the significance of the self-powered operation of UV PDs and the charge transfer mechanism are discussed with the aid of the energy band diagram. The substantial photocurrent increment with varying applied potential leads to narrowing the photo potential in the interface. The excitonic bound states present in p-GaN NWs/n-Si heterojunction is further elucidated. As a result, the heterojunction PDs demonstrate the high responsivity, detectivity, and external quantum efficiency of 134 mA W−1, 3.73 × 1013 Jones, and 51% respectively, at 0.1 V low applied potential under the reverse bias condition. The proposed work provides an archetype for Mg doping in GaN NWs ensembles, which will help to facilitate the heterojunction with n-Si to unleash the potential of self-powered UV PDs.

Study of intrinsic point defects in γ-In2Se3 based on first principles calculations for the realization of an efficient UV photodetector

In 2 Se 3 have attracted researcher’s attention due to its potential optoelectronic and memory device applications, having various polymorphs with few of them having layered structure. There exists a non-layered phase with vacancy ordered in screw form known as γ-In 2 Se 3 , whose properties are found to get affected majorly by the presence of defects. Here, the first principles calculations based on the density functional theory are performed to study the intrinsic point defects in defect wurtzite structure of γ-In 2 Se 3 using GGA-PBE approximations. Thermodynamic charge transitions based on the formation energy of the defects are determined for all native defects, V In , V Se , In i , Se i , Se In , In Se , under In-rich and Se-rich experimental growth conditions. The charge transition remains the same but transition energies differ for possible coordination of Se vacancies, whereas the charge transition as well as transition energy vary for different coordination sites of In vacancies. The In interstitial, In i is the most favourable defect site under In-rich conditions whereas Se In at the VBM and V In1 near CBM are dominating under Se-rich conditions. The origin of n-type conductivity of γ-In 2 Se 3 is found to be the presence of In i interstitials and In Se antisite in the defect wurtzite γ-In 2 Se 3 . Further, the films grown using PLD shows an n-type conductivity under In-rich conditions leading to a good performance with photo responsivity and specific detectivity of 5.22 × 10 2 A/W and 5.08 × 10 13 Jones. The understanding of these vacancies determines their thermodynamic behaviour which can help for the controlled growth of γ-In 2 Se 3 which leads to better device performance. • Thermodynamic transition states are predicted for γ-In 2 Se 3 under In-rich and Se-rich growth conditions using first principles study. • Origin of n-type conductivity of γ-In 2 Se 3 is found to be the presence of In i and In Se and V Se is observed to introduce the in-gap states. • Highly crystalline n-type γ-In 2 Se 3 thin films are optimized under the In-rich growth conditions using PLD technique. • High concentrations of In i and In Se are identified using PL studies. • High responsivity and detectivity is achieved for the prepared device indicating low trap states due to V Se .

Solution processed and highly efficient UV-photodetector based on CsPbBr3 perovskite-polymer composite film

All inorganic cesium lead bromide (CsPbBr3) perovskite is being extensively applied to optoelectronics due to its facile solution processability and extraordinary optical properties. However, the expansion of its implementation in optoelectronic devices is being hindered due to the poor surface coverage of its film, inefficient charge transportation, long-term instability, and requirements of complex fabrication techniques. Here, a facile solution-processed composite perovskite film composed of CsPbBr3 polycrystals merged with polymers such as polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) has been introduced to act as a light absorber for efficient ultraviolet (UV) light detection. The as-used polymers in the composite film have improved the surface coverage, surface passivation, light absorption, stability, charge carrier lifetime due to the high UV-Absorption tendency of CsPbBr3 and transport capability strengthened by the good ionic conduction of PEO, which results in an efficient UV-photodetection. Compared to the pristine CsPbBr3 film-based PD, the CsPbBr3-polymer based PD has achieved a high photo-to-dark current ratio, responsivity and specific detectivity of up to 106, 55.71 AW−1 and 8.07 × 1013 Jones, respectively, at a very low bias voltage of 0.2 V using 365 nm light source. The device has shown excellent stability of over 3 weeks under ambient environmental conditions.

Tailoring the interface assembly of mesoporous TiO2 on BTO film toward high-performance UV photodetectors

A heterojunction film consisting of BaTiO3@mesoporous TiO2 was engineered via an interface assembly strategy and spin-coating to fabricate a highly efficient UV photodetector.

Study of Intrinsic Point Defects in Γ-In2se3 for the Realization of an Efficient Uv Photodetector

Study of Intrinsic Point Defects in Γ-In2se3 for the Realization of an Efficient Uv Photodetector

A UV-enhanced, self-powered detector with graphene p–n junction grown in situ on SiC(0001) with periodic boron ion modulation

Graphene p–n junctions hold great potential in the fields of electronic and optoelectronic devices. Here, we develop a scheme of the in situ growth of an epitaxial graphene (EG) lateral p–n junction on a semi-insulating SiC (0001) substrate with periodic boron ion implantation, and utilizing the advantages of EG, SiC, and p–n junctions in a two-terminal device at the same time, a high-performance UV-enhanced self-powered photodetector is prepared based on an EG p–n junction with a maximum Fermi level difference of about 210 mV. Moreover, when a 325-nm laser locally irradiates the p-terminal of the device, its responsivity is about six times higher than when the laser locally irradiates the n-terminal. This indicates that EG on SiC with a p-type modulated subsurface is conducive to designing efficient UV photodetectors in which SiC serves as the gain medium. All of these characteristics facilitate the growth of EG p–n junctions on a wafer scale and the fabrication of EG p–n junctions for optoelectronic and electronic devices using standard semiconductor synthesis procedures.

Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications

The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.

Efficient UV photodetectors based on Ni-doped ZnS nanoparticles prepared by facial chemical reduction method

Ni-doped ZnS nanoparticles are synthesized by simple hydrothermal process for the utilization in UV photodetectors. Surface morphology of the prepared samples is investigated through high resolution transmission electron microscopy (HRTEM), which reveals that the prepared nanoparticles are smaller than 20 nm. The well visualized selected area electron diffraction rings suggests the nanocrystalline nature of the prepared nanoparticles with (hkl) planes (111), (220) and (311). The structural analysis is done by x-ray diffraction (XRD) studies; which reveal the decrease in crystallite size with increase in Ni-doping concentration. The device performance of the photodetectors is tested under UV-A light (wavelength ≈365 nm) and found that the ability of the prepared devices increases with increase in Ni-doping concentration. This can be attributed to the enhanced surface to volume ratio and increase in charge carrier concentration. The adsorption-desorption of oxygen molecules on the nanoparticles' surface is considered to be the mechanism for UV photodetection.

Determination of valence and conduction band offsets in Zn0.98Fe0.02O/ZnO hetero-junction thin films grown in oxygen environment by pulsed laser deposition technique: A study of efficient UV photodetectors

Here we present ZnO based thin films deposited in oxygen environment by pulsed laser deposition technique for UV photodetection applications. The valence and conduction band alignments are the key parameter required in understanding the type of charge carrier participating in conduction process. The valence and conduction band offset measurements have been carried out using the X-ray photoelectron spectroscopy (XPS) on the pristine ZnO, Fe (2 wt%) -doped ZnO (Zn0.98Fe0.02O) and the hetero-junction of Zn0.98Fe0.02O with ZnO (Zn0.98Fe0.02O/ZnO). XPS studies revealed that the valence band is upward shifted with 0.37 eV, whereas, there is a downward shifting of −0.393 eV in the conduction band. Structural analysis of the deposited films has been done using X-ray diffraction studies, which revealed the polycrystalline nature of all the films having wurtzite crystal phase. AFM studies suggest that the size of the grains decreases with Fe-doping in ZnO network due to different ionic radii of Zn and Fe. UV–Vis studies suggest the decrease in optical band gap with Fe-doping and hetero-junction formation. The optical band gap energy has also been obtained from the fitting of experimental data of absorption spectra with Mott -Davis's model and Hydrogenic excitonic model. Both the models are well corroborated with each other. The photoconduction behavior of the deposited films has been analyzed under UV light. The pristine ZnO film has a photoresponse of about 25% which is found to increase in Zn0.98Fe0.02O (∼36%) film. The responsivity values are found to be 1.56, 2.17 and 1.86 mA/W for the pristine ZnO, Zn0.98Fe0.02O and Zn0.98Fe0.02O/ZnO thin films, respectively.

A highly efficient UV photodetector based on a ZnO microwire p–n homojunction

A highly efficient ultraviolet photodetector was successfully obtained based on a Sb-doped p-type ZnO microwire p–n homojunction which consisted of a single Sb-doped p-type ZnO microwire and a single undoped ZnO microwire. The ultralong Sb-doped ZnO single crystalline microwires were synthesized via a chemical vapor deposition method. The ZnO microwire homojunction showed well-defined rectification characteristics, which indicated the p-type conductivity of the Sb-doped ZnO microwire. An ultraviolet photodetector with an external quantum efficiency of 64.5% was obtained based on the ZnO microwire p–n homojunction. The photodetector showed high wavelength selectivity with a full width at half maximum of 6 nm for the photoresponse peak located at 386 nm.