Excellent Photoresponse Research Articles

Van der Waals ZnO/HfSn2N4 Heterojunction with Exceptional Photoresponse for Photodetectors.

Two-dimensional van der Waals heterojunctions represent a promising avenue for a spectrum of optoelectronic endeavors. Nonetheless, their deployment has been somewhat constrained by the suboptimal efficiency of the photocurrent generated. In this article, a ZnO/HfSn2N4 heterojunction is proposed to achieve high photoresponse efficiency. First-principles calculations are utilized to confirm that this heterojunction possesses thermal stability with a direct bandgap (1.36 eV). It exhibits a high light absorption coefficient and high carrier mobility (2.51 × 103 cm2 V-1 s-1), and biaxial strain has a significant effect on the modulation of the band structure. As the tensile strain increases, the bandgap changes nonlinearly, transitioning from a type-II to a type-I heterojunction. When compressive strain increases, the bandgap decreases. Quantum transport simulations are employed to calculate the density of states and transmission spectrum of the ZnO/HfSn2N4 model, verifying its excellent photoresponse (a photocurrent peak reaching 4.93 a02/photon and an extinction ratio peak of 75.1). It shows that the ZnO/HfSn2N4 heterojunction is a potentially efficient photodetector.

Hydrogen chloride treated InAs quantum dot thin film phototransistor for ultrahigh responsivity

Indium Arsenide (InAs) colloidal quantum dots (CQDs) are emerging candidates for infrared photodetector applications owing to their excellent optoelectronic properties and low toxicity. However, low electron mobility stemming from its unique surface chemistry hinders its practical application. Through comprehensive structural and chemical analyses, we optimized the one-step HCl treatment to achieve stoichiometric balance, a well-passivated surface with low defect density, and an improved coupling effect by reducing the interparticle distance. Subsequently, a near infrared photodetector at a wavelength of 980 nm was fabricated with the modified InAs QDs in thin film transistor structure by all-solution process, showing remarkable electron mobility enhancement of up to 3.15 cm2/V∙s. The thin film phototransistor exhibited excellent photoresponse with a responsivity of 5.45 × 103 A/W, external quantum efficiency of 6.90 × 105%, and a linear dynamic range of 50 dB. This achievement represents the highest responsivity observed in an InAs QD-based phototransistor device, demonstrating its potential for lead-free infrared (IR) region optoelectronic applications.

Ultrahigh-performance heterojunction bipolar phototransistor enabled by bilateral piezoelectric charge modulation effect

Heterojunction photodiodes based on p-n junction with enhanced piezo-phototronic effect have been extensively studied. However, the photoresponsivity of conventional photodiodes is small due to the natural zero current gain. Heterojunction phototransistor usually has greater photoresponsivity due to the non-zero current gain. More importantly, heterojunction phototransistor owns two interfaces, offering the opportunity to introduce the bilateral piezoelectric charge modulation effect for further performance enhancement compared to the conventional single-interface piezo-phototronic effect in photodiode. In this work, a base-floating heterojunction bipolar phototransistor (FHPT) based on n-ZnO/p-Si/n-ZnO structure with a spectral detection range from ultraviolet (UV)–visible is demonstrated. The positive piezoelectric charge generated at the two interfaces of the collector junction and the emitter junction, combined with the optimal base width and low resistance base doping concentration of the FHPT, leads to an excellent photoresponsivity (18046 A/W, 365 nm), high detectivity (5.7×1012 Jones), and a wider modulation (7120 %). The physical mechanism leading to the ultrahigh performance is attributed to the cooperative positive piezoelectric charge at the two interfaces, simultaneously reducing the effective base width and lowering the emitter junction barrier. This work illustrates the regulation of heterojunction phototransistor performance by the bilateral piezoelectric charge modulation effect, providing insightful guidance to high-performance phototransistor design.

MBE-grown ZnTe epitaxial layer based broadband photodetector with high response and excellent switching characteristics

Zinc telluride (ZnTe) epitaxial layers were grown on gallium arsenide (GaAs) (211) substrate at different growth temperatures by molecular beam epitaxy. The fabricated interdigitated metal semiconductor metal configuration-based photodetector (PD) on ZnTe epitaxial layers exhibited a stable and excellent photo response in a broad spectral range (250–550 nm) up to 125 °C. The room temperature and higher temperature (125 °C) values of maximum current, spectral responsivity and detectivity at an applied bias of 5 V and 550 nm wavelength were 3.5 × 10−8 A, 0.1 A W−1 and 1 × 1011 Jones and 1.7 × 10−6 A, 2.5 A W−1 and 1.5 × 1011 Jones, respectively. The maximum photo-to-dark-current ratio (PDCR) value at zero bias and 100 °C was obtained for the ZnTe layer grown at an optimum growth temperature of 380 °C. The high PDCR value exhibits the self-powered capability of the detector. Furthermore, the detector exhibits good on–off switching to the illuminating light with rise and decay times less than 0.29 s and 0.4 s, respectively, at room temperature. The dependence of the photo response on material quality was analysed by varying the substrate growth temperature. The broadband responsivity of the ZnTe-based PD shows its capability as a multicolour detector in the UV and visible region with the use of suitable blocking filters.

Degradation performance and mechanism of VOCs in asphalt by alkali metal-doped La2Ce2O7-based fluorite through pyroelectric and photocatalytic synergy

Under high-temperature construction conditions, the use of asphalt can release a large amount of volatile organic compounds (VOCs), which has adverse effect on the environment and human health. Part of fluorite oxides show potential application in VOCs conversion due to their excellent photoresponse and chemical stability in addition to ferroelectricity, piezoelectricity and pyroelectricity properties. In this paper, La2Ce2O7-based fluorite was modified with alkali metal doping and its photo-thermal coupling catalytic effects on the degradation performance of VOCs in asphalt were investigated. The results show that the fluorite catalysts La1.85A0.15Ce2O7 (A=Li, Na, K, Rb, Cs) have efficient electron-hole pair separation ability. Among them, the Rb+ doped La2Ce2O7 sample not only has stronger pyroelectric effect due to increased lattice distortion and oxygen vacancies, but also has the best photogenerated charge transport property and more favorable valence band position for oxidation reaction. Under the photo-thermal synergistic effect, the catalytic degradation performance of VOCs in asphalt by Rb+ doped La2Ce2O7 catalyst can reach 82.61 % at 50 min. Additionally, dynamic shear rheological tests indicate that the addition of catalysts at this blending ratio can enhance the rutting resistance of the asphalt material. This study introduces an innovative approach to enhance the efficiency of multi-field coupled degradation processes of volatile organic compounds (VOCs) in asphalt.

Nitrogen-Doped 3D-Graphene Advances Near-Infrared Photodetector for Logic Circuits and Image Sensors Overcoming 2D Limitations.

The limitations of two-dimensional (2D) graphene in broadband photodetector are overcome by integrating nitrogen (N) doping into three-dimensional (3D) structures within silicon (Si) via plasma-assisted chemical vapor deposition (PACVD) technology. This contributes to the construction of vertical Schottky heterojunction broad-spectrum photodetectors and applications in logic devices and image sensors. The natural nanoscale resonant cavity structure of 3D-graphene enhances photon capture efficiency, thereby increasing photocarrier generation. N-doping can fine-tune the electronic structure, advancing the Schottky barrier height and reducing dark current. The as-fabricated photodetector exhibits exceptional self-driven photoresponse, especially at 1550 nm, with an excellent photoresponsivity (79.6 A/W), specific detectivity (1013 Jones), and rapid response of 130 μs. Moreover, it enables logic circuits, high-resolution pattern image recognition, and broadband spectra recording across the visible to near-infrared range (400-1550 nm). This research will provide new views and technical support for the development and widespread application of high-performance semiconductor-based graphene broadband detectors.

Polarization-sensitive and wide-spectrum photodetector from ultraviolet to near-infrared light based on 2D tellurium at room temperature

Two-dimensional (2D) materials have emerged as promising candidates for photodetection applications, due to their unique structural and optical properties. Herein, we conducted a comprehensive investigation of the 2D Te-based photodetector. The crystal structure, angle-resolved polarized Raman (ARPR) spectroscopy, and theoretical analysis demonstrate the in-plane lattice anisotropy of Te, underlining its suitability for polarization-dependent photodetection. Photocurrent measurements over a broad spectral range (from 365 to 1310 nm) reveal excellent photoresponse characteristics, with responsivity (Rλ) and detectivity (D*) values reaching up to 1189 A/W and 11.51 × 108 Jones, respectively, under 1064 nm illumination. Furthermore, the Te-based photodetector exhibits superior stability, retaining approximately 90 % of its initial performance after six months of ambient exposure. Polarization-sensitive photodetection experiments show significant dichroism ratios (up to 4.6 for 1064 nm illumination), emphasizing the potential of 2D Te for advanced polarization applications. The combination of the broad spectral response, high anisotropy ratio, and long-term stability positions 2D Te as a promising candidate for future photodetection technologies.

Interface reconstruction of MXene-Ti3C2 doped CeO2 nanorods for remarked photocatalytic ammonia synthesis

Prospective photocatalytic ammonia synthesis process has received more attentions but quite challenging with the low visible light utilization and weak N2 molecule absorption ability around the photocatalysts. Herein, interface reconstruction of MXene-Ti3C2/CeO2 composites with high-concentration active sites through the carbon-doped process are presented firstly, and obvious transition zones with the three-phase reaction interface are formed in the as-prepared catalysts. The optimal co-doped sample demonstrates an excellent photo response in the visible light region, the strongest chemisorption activity and the most active sites. Moreover, much more in-situ extra oxygen defects are also produced under light irradiation. It is expected that the double decorated catalyst shows a remarked ammonia production rate of above 0.76 mmol gcal−1·h−1 under visible-light illumination and a higher apparent quantum efficiency of 1.08 % at 420 nm, which is one of the most completive properties for the photocatalytic N2 fixation at present.

Gate‐Modulated and Polarization‐Sensitive Photodetector Based on the MoS2/PdSe2 Out‐Of‐Plane Van Der Waals Heterostructure

AbstractPhotodetectors with good polarization detection ability are promising in many applications, such as remote sensing imaging and environmental monitoring. However, the traditional polarization detection systems fall short in meeting integration demands of the integrated‐circuits field due to additional optical elements. The emerging 2D materials with in‐plane anisotropic structures provide a possible method to fabricate remarkable polarization detectors. Modulating the band structure by gate voltage is an important strategy for developing optoelectronic devices. Herein, a polarized photodetector based on PdSe2/MoS2 out‐of‐plane heterojunction is fabricated. Due to its unique out‐of‐plane heterostructure, the device exhibits excellent photoresponse characteristics and polarization sensitivity, including an excellent responsivity of 10.19A/W, an extremely high external quantum efficiency of 2429%, a fast rise/decay time of 68/192 µs, and a high photocurrent anisotropy ratio of 3.09. Based on the adjustment of the built‐in electric field through gate voltage, the performance of the device can be accordingly modulated. As the gate voltage increases from −30 to 30 V, the responsivity gradually increases from 7.5 to 13A/W and the detectivity increases from 1.53 to 2.63 × 109Jones. Finally, its olarization imaging ability is demonstrated at different polarization angles. The findings indicate that PdSe2/MoS2 devices exhibit significant potential for polarized photoelectric detection.

Modulate the work function of MXene in MXene/InGaN heterojunction for visible light photodetector

MXene/InGaN heterojunction photodetectors with simple structure and superior optoelectronic performance are considered a viable option for optical communication. However, the integration of MXene with InGaN faces the problem of a relatively low Schottky barrier, leading to electron backflow, which hinders the separation of carriers and limits the photoresponse of photodetectors. Herein, high-performance MXene/InGaN heterojunction photodetectors were fabricated, and the work function of Ti3C2TX was modulated to explore its effect on the performance of the photodetectors. The ascorbic acid treatment increased the work function of MXene from 4.20 to 4.34 eV, enhancing the Schottky barrier height of the heterojunction from 0.56 to 0.70 eV. The devices exhibit excellent photoresponse performances, such as a responsivity of 0.133 A W−1 and a specific detectivity of 2.81 × 1011 Jones at −1 V bias, as well as a short rise/decay time of 37.49/110 μs at 0 V bias. Additionally, the photodetectors achieve high stability that can maintain over 95% of the initial value after 3 months. This work indicates the potential for utilizing tunable MXene work function to construct high-performance optoelectronic devices for visible light applications.

Ligand-free Cs2PdBr6 perovskite microcrystals with narrow bandgap and high photoelectrochemical performance in aqueous solution

The exploration of efficient lead-free perovskite photoelectric active materials to develop high-performance photoelectrochemical (PEC) systems in aqueous solution is crucial to expand their PEC applications. Herein, we successfully constructed a high-performance PEC platform using ligand-free perovskite Cs2PdBr6 microcrystals (MCs) as the photoactive substance. The Cs2PdBr6 MCs showed narrow bandgap, wide absorption range, high electronic mobility and good stability in aqueous solutions. Particularly, the Cs2PdBr6 MCs exhibited an excellent photoresponse, the photocurrent density could reach as high as 98 μA/cm2 under 10.18 mW/cm2 light irradiation in the absence of other electron acceptors. In addition of the extremely wide range of response wavelength, wide pH range and accelerated interfacial carrier transfer, the Cs2PdBr6 MCs demonstrated the significant potential of photocathode active material for applications in PEC sensors and optoelectronic devices. Therefore, this work indicates that Cs2PdBr6 MCs design is a highly efficient way to solve the intrinsic issues of perovskite material, predicting a promising strategy for high performance PEC application in aqueous ambience.

Two-Dimensional GeS/SnSe2 Tunneling Photodiode with Bidirectional Photoresponse and High Polarization Sensitivity.

A two-dimensional (2D) broken-gap (type-III) p-n heterojunction has a unique charge transport mechanism because of nonoverlapping energy bands. In light of this, type-III band alignment can be used in tunneling field-effect transistors (TFETs) and Esaki diodes with tunable operation and low consumption by highlighting the advantages of tunneling mechanisms. In recent years, 2D tunneling photodiodes have gradually attracted attention for novel optoelectronic performance with a combination of strong light-matter interaction and tunable band alignment. However, an in-depth understanding of the tunneling mechanisms should be further investigated, especially for developing electronic and optoelectronic applications. Here, we report a type-III tunneling photodiode based on a 2D multilayered p-GeS/n+-SnSe2 heterostructure, which is first fabricated by the mechanical exfoliation and dry transfer method. Through the Simmons approximation, its various tunneling transport mechanisms dependent on bias and light are demonstrated as the origin of excellent bidirectional photoresponse performance. Moreover, compared to the traditional p-n photodiode, the device enables bidirectional photoresponse capability, including maximum responsivity values of 43 and 8.7 A/W at Vds = 1 and -1 V, respectively, with distinctive photoactive regions from the scanning photocurrent mapping. Noticeably, benefiting from the in-plane anisotropic structure of GeS, the device exhibits an enhanced photocurrent anisotropic ratio of 9, driven by the broader depletion region at Vds = -3 V under 635 nm irradiation. Above all, the results suggest that our designed architecture can be potentially applied to CMOS imaging sensors and polarization-sensitive photodetectors.

Constructing interface chemical coupling S-scheme heterojunction MoO3-x@PPy for enhancing photocatalytic oxidative desulfurization performance: Adjusting LSPR effect via oxygen vacancy engineering

Construction of photocatalyst that combines excellent electron transfer and photoresponse capabilities to enhance photocatalytic performance remains a challenging task. In this work, interfacial Mo-N bonds and vacancy engineering collaborative modified MoO3-x@polypyrrole (MP) S-scheme heterojunction is rational designed for efficient photocatalytic oxidative desulfurization. The addition of polypyrrole introduces rich defects which inducing the localized surface plasmon resonance (LSPR) effect and enhancing light absorption. Furthermore, the combination facilitates the formation of Mo-N bonds. The modifications amplify the built-in electric field and conduct the efficacious separation of photogenerated carriers. With the synergism of LSPR effect and interfacial chemical Mo-N bonds, the optimal MP photocatalyst displays attractive desulfurization rate of 100% for dibenzothiophene (DBT) in 60 min under illumination, touching the objective of ultra-deep desulfurization. The study extends a novel understanding of the impact of LSPR effect and heterojunction interface charge transfer on the photocatalytic desulfurization ability.

Symmetry-Reduction Enhanced Polarization-Sensitive Photoresponse Based on One-Dimensional van der Waals Materials.

Designing high-performance polarization-sensitive photodetectors is essential for photonic device applications. Anisotropic one-dimensional (1D) van der Waals (vdW) materials have provided a promising platform to that end. Despite significant advances in 1D vdW photonic devices, their performance is still far from delivering practical potential. Herein, we propose the design of high-performance polarization-sensitive photodetectors using unique 1D vdW materials. By leveraging the chemical vapor transport technique, we successfully fabricate high-quality 1D vdW Nb2Pd1-xSe5 (x = 0.29) nanowires. The 1D vdW Nb2Pd1-xSe5 photodetector exhibits a high mobility of ∼56 cm2/(V s) and superior photoresponse performance, including a high responsivity of 1A/W and an ultrafast response time of ∼8 μs under 638 nm illumination. Moreover, the 1D vdW Nb2Pd1-xSe5 photodetector demonstrates excellent polarization-sensitive photoresponse with a degree of linear polarization (DOLP) up to 0.85 and can be modulated by adjusting the gate voltage, laser power density, and wavelength. Those exceptional performance are believed to be relevant to the symmetry-reduction induced by the partial occupation of Pd sites. This study offers feasible approaches to enhance the anisotropy of 1D vdW materials and the modulation of their polarization-sensitive photoresponse, which may provide deep insights into the physical origin of anisotropic properties of 1D vdW materials.

Integrated GaN Prism Array Self‐Powered Photodetector on Si for Ultraviolet Imaging and Communication

AbstractTo realize the advantageous combination of microelectronic integrated circuit technology and photonic technology, the development of high‐speed, low‐power, and chip‐integrated photodetection devices is extremely critical. Here, a large‐scale on‐chip integration photodetector array on a Si wafer consisting of 21×21 GaN p‐n homojunction pixels is prepared. The GaN homojunction subunit has significant photovoltaic performance at a bias voltage of 0 V, including high responsivity of 229.5 mA W−1, outstanding specific detectivity of 2.46×1013 Jones (360 nm, 45.7 µW cm−2), and fast response speed of 240/290 µs. Especially, external quantum efficiency can reach 94% in the faint UV illumination at 0 V bias. The excellent photoresponse is confirmed by finite element analysis, which is resulted from an oversized built‐in potential at the p‐n homojunction interface. For exploring potential practical applicability of the device, the full range of active pixels is statistically analyzed. It is confirmed that the small relative deviation of the GaN array is extremely favorable for obtaining high‐resolution imaging capability. Moreover, the prepared device can be used as an optical data receiver for UV optical communication. With compatibility and integrability to Si‐based optoelectronics platforms, the devices are appealing for sensing, imaging and communications.

Interface‐Engineering Induced Swift and Controllable Solar‐Blind Photoresponse in Ga2O3/SiC Heterojunction Based on Unconventional Rectification Characteristics

AbstractGa2O3 photodetectors with demonstrated high sensitivity provide a potential subversive scheme for solar‐blind photodetection. However, the planar structure and the relatively slow response speed of the device have restricted the integration and application of Ga2O3 photodetectors. Herein, a narrow SiO2 barrier layer is introduced on the commercial SiC substrate, and a vertical photodetector is realized based on β‐Ga2O3/SiO2/SiC heterostructure with controllable tunneling effect by tailoring the band structure at the interface. The developed device exhibits unconventional rectification characteristics and photoresponse performance in different biasing modes owing to the controllable tunneling effect at the interface. In particular, the photodetector achieves a high responsivity (186.8 A W−1) under solar‐blind illumination at reverse bias, while exhibiting obvious advantages in dark current (3 pA), photo‐to‐dark current ratio (8.8 × 106), linear dynamic range (138.8 dB), and specific detectivity (1.4 × 1015 Jones) at forward bias. The photodetector also demonstrates excellent photoresponse stability after 6 months in air without encapsulation. In addition, an alternating biasing strategy, inspired by its bidirectional operability, is proposed to suppress the persistent photoconductivity effect and increase the decay speed by 1.23 × 105 times. This work provides a referable strategy for the further development of high‐performance Ga2O3‐based photoelectronics.

Flexible UV photodetector based on copper tetraiodogallate (CuGaI4) film

AbstractThe Cu‐based halide semiconductor CuGaI4 was prepared by a high‐temperature melting method. Optoelectronic characterization and density functional theory calculations of CuGaI4 reveal a direct bandgap of 2.9 eV. The corresponding UV photodetector (PD) based on CuGaI4 demonstrates excellent UV response and rapid response time. In addition, a flexible PD based on CuGaI4 is prepared, which also displays excellent photoresponse characteristics and mechanical stability. This work provides a systematic study of this novel Cu‐based halide semiconductor and demonstrates the great potential of CuGaI4 for future UV optoelectronic devices.

A Broadband Photodetector Based on Non-Layered MnS/WSe2 Type-I Heterojunctions with Ultrahigh Photoresponsivity and Fast Photoresponse.

The separation of photogenerated electron-hole pairs is crucial for the construction of high-performance and wide-band responsive photodetectors. The type-I heterojunction as a photodetector is seldomly studied due to its limited separation of the carriers and narrow optical response. In this work, we demonstrated that the high performance of type-I heterojunction as a broadband photodetector can be obtained by rational design of the band alignment and proper modulation from external electric field. The heterojunction device is fabricated by vertical stacking of non-layered MnS and WSe2 flakes. Its type-I band structure is confirmed by the first-principles calculations. The MnS/WSe2 heterojunction presents a wide optical detecting range spanning from 365 nm to 1550 nm. It exhibits the characteristics of bidirectional transportation, a current on/off ratio over 103, and an excellent photoresponsivity of 108 A W-1 in the visible range. Furthermore, the response time of the device is 19 ms (rise time) and 10 ms (fall time), which is much faster than that of its constituents MnS and WSe2. The facilitation of carrier accumulation caused by the interfacial band bending is thought to be critical to the photoresponse performance of the heterojunction. In addition, the device can operate in self-powered mode, indicating a photovoltaic effect.

On-Substrate Fabrication of CsPbBr3 Single-Crystal Microstructures via Nanoparticle Self-Assembly-Assisted Low-Temperature Sintering.

The growth of all-inorganic perovskite single-crystal microstructures on substrates is a promising approach for constructing photonic and electronic microdevices. However, current preparation methods typically involve direct control of ions or atoms, which often depends on specific lattice-matched substrates for epitaxial growth and other stringent conditions that limit the mild preparation and flexibility of device integration. Herein, we present the on-substrate fabrication of CsPbBr3 single-crystal microstructures obtained via a nanoparticle self-assembly assisted low-temperature sintering (NSALS) method. Sintering guided by self-assembled atomically oriented superlattice embryos facilitated the formation of single-crystal microstructures under mild conditions without substrate dependence. The as-prepared on-substrate microstructures exhibited a consistent out-of-plane orientation with a carrier lifetime of up to 82.7 ns. Photodetectors fabricated by using these microstructures exhibited an excellent photoresponse of 9.15 A/W, and the dynamic optical response had a relative standard deviation as low as 0.1831%. The discrete photosensor microarray chip with 174000 pixels in a 100 mm2 area showed a response difference of less than 6%. This method of nanoscale particle-controlled single crystal growth on a substrate offers a perspective for mild-condition preparation and in situ repair of crystals of various types. This advancement can propel the flexible integration and widespread application of perovskite devices.

Sm, Nd doped BiFeO3 epitaxial film for photodetector with extremely large on–off current ratio

BiFeO3 is one of the star materials in the field of ferroelectric photovoltaic for its relatively narrow bandgap (2.2–2.7 eV) and better visible light absorption. However, a high temperature over 600 °C is indispensable in the usual BiFeO3 growth process, which may lead to impure phase, interdiffusion of components near the interface, oxygen vacancy and ferrous iron ions, which will result in large leakage current and greatly aggravate the ferroelectricity and photoelectric response. Here we prepared Sm, Nd doped epitaxial BiFeO3 film via a rapid microwave assisted hydrothermal process at low temperature. The Bi0.9Sm0.5Nd0.5FeO3 film exhibits narrow bandgap (1.35 eV) and photo response to red light, the on–off current ratio reaches over 105. The decrease in band gap and +2/+3 variable element doping are responsible for the excellent photo response. The excellent photo response performances are much better than any previously reported BiFeO3 films, which has great potential for applications in photodetection, ferroelectric photovoltaic and optoelectronic devices.