High Photoresponsivity Research Articles

Fast Fabrication of WS2/Bi2Se3 Heterostructures for High-Performance Photodetection.

Two-dimensional (2D) material heterostructures have attracted considerable attention owing to their interesting and novel physical properties, which expand the possibilities for future optoelectronic, photovoltaic, and nanoelectronic applications. A portable, fast, and deterministic transfer technique is highly needed for the fabrication of heterostructures. Herein, we report a fast half-wet poly(dimethylsiloxane) (PDMS) transfer process utilizing the change of adhesion energy with the help of micron-sized water droplets. Using this method, a vertical stacking of the WS2/Bi2Se3 heterostructure with a straddling band configuration is successfully assembled on a fluorophlogopite substrate. Thanks to the complementary band gaps and high efficiency of interfacial charge transfer, the photodetector based on the heterostructure exhibits a superior responsivity of 109.9 A W-1 for a visible incident light at 473 nm and 26.7 A W-1 for a 1064 nm near-infrared illumination. Such high photoresponsivity of the heterostructure demonstrates that our transfer method not only owns time efficiency but also ensures high quality of the heterointerface. Our study may open new pathways to the fast and massive fabrication of various vertical 2D heterostructures for applications in twistronics/valleytronics and other band engineering devices.

Wafer-scale high sensitive UV photodetectors based on novel AlGaN/n-GaN/p-GaN heterostructure HEMT

We report a novel high sensitive ultraviolet (UV) photodetector based on AlGaN/n-GaN/p-GaN heterostructure high electron mobility transistor (HEMT) on sapphire substrates and have prepared four types of devices with identical lengths but different widths of the effective region on one wafer. Since the existence of the built-in electric field within p-GaN and n-GaN, the two-dimensional electron gases (2DEGs) at the AlGaN/n-GaN interface is effectively depleted, leading to ultra-low dark current at pA level. Under UV LED irradiation with wavelength of 365 nm, the photodetectors demonstrate extremely high light on/off ratio (Ilight/Idark) of about 106 and high photoresponse speed with the rise time (τrise)/decay time (τdecay) of 1.53 ms/2.21 ms at Vds = -5 V under light power density of 236.97 mW/cm2. Furthermore, the R of the photodetector reaches 9.12 A/W, the EQE and D* are as high as 3100 % and 1.95 × 1013 Jones, respectively, indicating overall high performances of the device in terms of photoresponsivity, EQE, detectivity and robust stability. The proposed photodetectors with merits of p-GaN etchless compared with conventional E-mode p-GaN HEMT and wafer-scale mass production may pave the way for the application of UV communication, Internet of Things and medical treatment.

Centimeter-Scale PdS2 Ultrathin Films with High Mobility and Broadband Photoresponse.

2D materials with mixed crystal phase will lead to the nonuniformity of performance and go against the practical application. Therefore, it is of great significance to develop a valid method to synthesize 2D materials with typical stoichiometry. Here, 2D palladium sulfides with centimeter scale and uniform stoichiometric ratio are synthesized via controlling the sulfurization temperature of palladium thin films. The relationship between sulfurization temperature and products is investigated in depth. Besides, the high-quality 2D PdS2 films are synthesized via sulfurization at the temperature of 450-550°C, which would be compatible with back-end-of-line processes in semiconductor industry with considering of process temperature. The PdS2 films show an n-type semiconducting behavior with high mobility of 10.4 cm2 V-1 s-1 . The PdS2 photodetector presents a broadband photoresponse from 450 to 1550nm. These findings provide a reliable way to synthesizing high-quality and large-area 2D materials with uniform crystal phase. The result suggests that 2D PdS2 has significant potential in future nanoelectronics and optoelectronic applications.

2D MXene/ 1D GaN van der Waals heterojunction for self-powered UV photodetector

MXene's two-dimensional (2D) morphology, metallic electrical conductivity, and optical transparency characteristics have been widely utilized to uplift the performance of diverse optoelectronic devices. In this study, we demonstrate a simple spin-coating of 2D MXene nanosheets on 1D GaN nanorods (NRs) to establish a van der Waals (vdW) Schottky junction, which is efficient to detect UV radiation (λ = 382 nm) without requiring the external power supply. The built-in electric field developed through vdW Schottky junction formation stimulates the separation of electron–hole pairs and thereby facilitates the MXene/GaN NRs device to exhibit better UV detection performance than the pristine GaN NRs device. The performance of both pristine GaN and MXene/GaN NRs devices is compared by tuning the UV radiation power density in the range of 0.33–1.35 mW/cm2. Notably, the self-powered MXene/GaN NRs photodetector demonstrated the characteristics of high photoresponsivity (48.6 mA/W), detectivity (5.9 × 1012 Jones), and external quantum efficiency (543%). These characteristics signify the suitability of MXene/GaN self-powered photodetectors for various applications, including imaging, sensing networks, and energy-saving communication.

High-Performance Diamond Phototransistor with Gate Controllable Gain and Speed.

This paper presents a fabricated solar-blind phototransistor based on hydrogen-terminated diamond. The phototransistor shows a large photocurrent and enhancement of responsivity over conventional two-terminal diamond-based photodetector. These enhancement effects are owing to the internal gain of the phototransistor. The fabricated phototransistor exhibits a high photoresponsivity (R) of 2.16 × 104 A/W and a detectivity (D*) of 9.63 × 1011 jones, with gate voltage (VG) and drain voltage of approximately -1.5 V and -5 V, respectively, under 213 nm light illumination. Even at ultralow operating voltage of -0.01 V, the device records satisfactory performance with R and D* of 146.7 A/W and 6.19 × 1010 jones, respectively. By adjusting the VG, photocurrent generation in the device can be continuously tuned from the fast photoconductive effect to the optical gating effect with high optical gain. When VG increases from 1.4 to 2.4 V, the decay time decreases from 1512.0 to 25.5 ms. Therefore, responsivity, dark current, Iphoto/Idark, and decay time of the device can be well tuned by VG.

Self‐Powered Photodetector Based on Perovskite/NiOx Heterostructure for Sensitive Visible Light and X‐Ray Detection

AbstractSelf‐powered halide perovskite X‐ray detectors have evoked busting interests because they present outstanding properties such as low power consumption, high sensitivity, and integrability without external power source. Nevertheless, existing self‐powered X‐ray detectors exhibit low sensitivity due to the insufficient charge separation and transport. Herein, a self‐powered photodetector for sensitive X‐ray and photodetection based on single‐crystalline perovskite FAPbBr3/NiOx heterostructure is demonstrated. The built‐in field of FAPbBr3/NiOx heterojunction provides a driving force for separation and transport of photoexcited carriers. Without an external power supply, the photodetector presents excellent photoresponse performance under 450 nm light illumination, including high photoresponsivity (123.6 mA W−1), good detectivity (D = 7.1 × 1011 Jones), and ultrafast response/recovery time (10/200 ns). Simultaneously, the device achieves photovoltaic effect of 0.80 V and a large mobility–lifetime product of 1.1 × 10−3 cm2 V−1, which enable a superior X‐ray sensitivity of 402 µC Gyair−1 cm−2 at zero bias voltage. These results imply that the simple combination of perovskite single crystal and a hole transporting layer provides a flexible platform for the realization of energy‐saving self‐powered photodetector in visible light and X‐rays.

Structural design of BaSi2 solar cells with a-SiC electron-selective transport layers

Sputter-deposited polycrystalline BaSi2 films capped with a 5 nm thick a-SiC layer showed high photoresponsivity. This means that the a-SiC layer functions as a capping layer to prevent surface oxidation of BaSi2. Based on the measured absorption edge, the electron affinity of the a-SiC layer, and the work function of the TiN layer, the a-SiC is considered to act as an electron transport layer (ETL) for the BaSi2 light absorber layer/a-SiC interlayer/TiN contact structure in a BaSi2 solar cell. Using a 10 nm thick p+-BaSi2 layer as a hole transport layer, we investigated the effect of the BaSi2/a-SiC layered structure on the device performance of a BaSi2-pn homojunction solar cell by a one-dimensional device simulator (AFORS-HET v2.5). The a-SiC ETL effectively separates photogenerated carriers and allows transport of electrons while blocking holes to achieve an efficiency of 22% for a 500 nm thick BaSi2 light absorber layer.

Room‐Temperature Self‐Powered Terahertz Photodetection in Ge‐Intercalated Topological Insulator GeBi4Te7

Topological insulators (TIs) are under rapid and intensive study in the fields of condensed matter physics, due to exotic electronic properties. Recent studies of photocurrent generation in topological surface states (TSS) properties have insufficient evidence to rule out that of bulk states, hindering the application in optoelectronics. Herein, the chemical vapor transport (CVT) synthesis of GeBi4Te7 crystal by the way of Ge intercalation is realized, enabling isolated Dirac points‐associated high‐mobility Dirac carriers and larger Seebeck coefficients. Then, the antenna‐coupled photodetector in GeBi4Te7 based on planar metal–TI–metal structure is reported, successfully realizing sensitive terahertz response without bias. According to the results, the GeBi4Te7‐based terahertz photodetector has a short response time and a high photoresponsivity (0.42 A W−1 at 0.107 THz and 0.6 A W−1 at 0.28 THz, respectively). The GeBi4Te7–graphene heterostructure can further improve the responsivity by more than two orders of magnitude, reaching 12 A W−1 at 0.107 THz. These findings bring up doable avenues for GeBi4Te7 materials’ low‐energy optoelectronic applications.

Photogating Effect of Atomically Thin Graphene/MoS2/MoTe2 van der Waals Heterostructures.

The development of short-wave infrared photodetectors based on various two-dimensional (2D) materials has recently attracted attention because of the ability of these devices to operate at room temperature. Although van der Waals heterostructures of 2D materials with type-II band alignment have significant potential for use in short-wave infrared photodetectors, there is a need to develop photodetectors with high photoresponsivity. In this study, we investigated the photogating of graphene using a monolayer-MoS2/monolayer-MoTe2 van der Waals heterostructure. By stacking MoS2/MoTe2 on graphene, we fabricated a broadband photodetector that exhibited a high photoresponsivity (>100 mA/W) and a low dark current (60 nA) over a wide wavelength range (488-1550 nm).

A two-dimensional Te/ReS2 van der Waals heterostructure photodetector with high photoresponsivity and fast photoresponse.

Two-dimensional (2D) semiconductors are the building blocks for high-performance optoelectronic devices. However, the performance of photoconductive photodetectors based on 2D semiconductors is hampered by low photoresponsivity and large dark current. Herein, a van der Waals heterostructure (vdWH) composed of rhenium disulfide (ReS2) and tellurium (Te) is fabricated. The Te/ReS2 vdWH photodetector exhibits a sensitive and broadband photoresponse and has high photoresponse on/off ratios under ultraviolet and visible light illumination, especially over 102 in visible light. The Te/ReS2 vdWH photodetector achieves the responsivity of 7.9 A W-1 at 365 nm, 3.02 A W-1 at 450 nm, 2.37 A W-1 at 532 nm, and 2.45 A W-1 at 660 nm. In addition, the device achieves a high specific detectivity of 1011 Jones and a fast photoresponse speed of 11.9 μs. Such high responsivity could be attributed to the efficient absorption of phonons by the Te/ReS2 vdWH and the high-quality heterostructure interfaces with a small amount of trap states. The highly crystalline structure of Te/ReS2 with a low density of defects reduces the grain boundary scattering, leading to the rapid diffusion of charge carriers. Moreover, the Te/ReS2 vdWH device exhibits a photovoltaic effect and can be employed as a self-powered photodetector (SPPD), which is sensitive to visible light of 450 nm, 532 nm, and 660 nm. Our findings demonstrate that the Te/ReS2 vdWH photodetector is an ideal building block for the next-generation electronic and optoelectronic devices in practical applications.

Photosensitisation of inkjet printed graphene with stable all-inorganic perovskite nanocrystals.

All-inorganic perovskite nanocrystals (NCs) with enhanced environmental stability are of particular interest for optoelectronic applications. Here we report on the formulation of CsPbX3 (X is Br or I) inks for inkjet deposition and utilise these NCs as photosensitive layers in graphene photodetectors, including those based on single layer graphene (SLG) as well as inkjet-printed graphene (iGr) devices. The performance of these photodetectors strongly depends on the device structure, geometry and the fabrication process. We achieve a high photoresponsivity, R > 106 A W-1 in the visible wavelength range and a spectral response controlled by the halide content of the perovskite NC ink. By utilising perovskite NCs, iGr and gold nanoparticle inks, we demonstrate a fully inkjet-printed photodetector with R ≈ 20 A W-1, which is the highest value reported to date for this type of device. The performance of the perovskite/graphene photodetectors is explained by transfer of photo-generated charge carriers from the perovskite NCs into graphene and charge transport through the iGr network. The perovskite ink developed here enabled realisation of stable and sensitive graphene-based photon detectors. Compatibility of inkjet deposition with conventional Si-technologies and with flexible substrates combined with high degree of design freedom provided by inkjet deposition offers opportunities for partially and fully printed optoelectronic devices for applications ranging from electronics to environmental sciences.

A fully printed ultrafast Si/WS2 quantum dot photodetector with very high responsivity over the UV to near-infrared region.

Two-dimensional (2D) semiconducting material-based photodetectors (PDs) with high responsivity and fast photo-response are of great interest for various applications such as optical communications, biomedical imaging, security surveillance, environmental monitoring, etc. Additive manufacturing such as 2D printing is a potentially less cumbersome and cost-effective alternative to conventional microdevice fabrication processes used in the production of PDs. Here, we have fabricated a Si/WS2 quantum dot-based heterostructure PD with a very short electrode gap of 40 μm by a simple printing process. The printed p-Si/n-WS2 PD shows an excellent photo-to-dark current ratio of 5121 under 405 nm illumination (23.8 mW cm-2). The printed photodetector exhibits a peak responsivity of 126 A W-1 and a peak detectivity of 9.24 × 1012 Jones over a very broad wavelength range (300-1100 nm), which is much superior to commercial Si PDs. A high external quantum efficiency of 3.9 × 104% and an ultrafast photoresponse (7.8 μs rise time and 9.5 μs fall time) make the device an attractive candidate as an efficient photodetector. The origin of high-performance photodetection is traced to a nearly defect-free interface at the heterojunction, leading to highly efficient charge separation and high photocurrent. Finally, the 2D-printed device exhibits good photodetection even in self-powered conditions, which is very attractive.

Bi2Te2Se and Sb2Te3 heterostructure based photodetectors with high responsivity and broadband photoresponse: experimental and theoretical analysis.

Topological insulators have emerged as one of the most promising candidates for the fabrication of novel electronic and optoelectronic devices due to the unique properties of nontrivial Dirac cones on the surface and a narrow bandgap in the bulk. In this work, the Sb2Te3 and Bi2Te2Se materials, and their heterostructure are fabricated by metal-organic chemical vapour deposition and evaporation techniques. Photodetection of these materials and their heterostructure shows that they detect light in a broadband range of 600 to 1100 nm with maximum photoresponse of Sb2Te3, Bi2Te2Se and Sb2Te3/Bi2Te2Se at 1100, 1000, and 1000 nm, respectively. The maximum responsivity values of Sb2Te3, Bi2Te2Se, and their heterostructure are 183, 341.8, and 245.9 A W-1 at 1000 nm, respectively. A computational study has also been done using density functional theory (DFT). Using the first-principles methods based on DFT, we have systematically investigated these topological insulators and their heterostructure's electronic and optical properties. The band structures of Sb2Te3 and Bi2Te2Se thin films (3 QL) and their heterostructure are calculated. The bandgaps of Sb2Te3 and Bi2Te2Se are 26.4 and 23 meV, respectively, while the Sb2Te3/Bi2Te2Se heterostructure shows metallic behaviour. For the optical properties, the dielectric function's real and imaginary parts are calculated using DFT and random phase approximation (RPA). It is observed that these topological materials and their heterostructure are light absorbers in a broadband range, with maximum absorption at 1.90, 2.40, and 3.21 eV.

Effect of MoO<sub>3</sub>-overlayer on MoS<sub>2</sub>-based photovoltaic photodetector performance

Photovoltaic device based on van der Waals heterojunction provides an effective way to develop high-performance, low-power consumption, ultra-integrated micro photodetection system. In this paper, we construct an asymmetric Au/MoS<sub>2</sub> Schottky junction to realize a planar MoS<sub>2</sub>-based photovoltaic device. In order to further improve the photoelectric performance of the device, we design a structure covering MoO<sub>3</sub> on the surface of MoS<sub>2</sub> to construct the heterojunction. Owing to the absorption properties of MoO<sub>3</sub> in visible light and the excellent light transmittance of the ultra-thin two-dimensional structure, the electrons involved in conducting in MoS<sub>2</sub> material are increased. In most of previous reports, the preparation methods and performance improvement of MoS<sub>2</sub>/MoO<sub>3</sub> heterojunctions were the focus of research, but little attention was paid to exploring the influence of overlayer on devices. Therefore, in this work, we investigate the influence of overlayer thickness on device performance. With the help of atomic layer deposition (ALD) method to control the film thickness, each of the MoO<sub>3</sub> materials with thickness of 4 nm, 12 nm and 20 nm (deposition periods of 10, 30 and 50, respectively) is covered on the surface of a MoS<sub>2</sub>-based photodetector. The photoelectric performance enhancement effects of three groups of heterojunction photodetectors are compared with each other. The results show that the thinner the MoO<sub>3</sub> layer, the more significant the enhancement effect of heterojunction photodetectors is. This is mainly attributed to the fact that ultra-thin MoO<sub>3</sub> layer not only has visible light absorption, but also reduces the influence of the covering layer on the light absorption of MoS<sub>2</sub>, thus achieving a heterojunction system with high light absorption efficiency. In addition, the interfacial electric field of the heterojunction effectively promotes the separation of photogenerated carriers, and the thinner the MoO<sub>3</sub> coating layer, the weaker the effect of introducing the interfacial defects of the heterojunction is. Therefore, the dark current gain effect of the device is effectively suppressed, which is beneficial to improving the response speed and optical detectivity of the device. Comparing with pure MoS<sub>2</sub> photovoltaic photodetectors, the photoresponsivity of MoS<sub>2</sub>/MoO<sub>3</sub> heterojunction device in this paper is enhanced nearly 10 times. The device exhibits a high photoresponse of ~916.121 A/W, a detectivity of ~2.74×10<sup>11</sup> Jones, and a fast response time of ~73 μs, showing that this design can effectively solve the low-responsiveness problem of planar photovoltaic device. In this study, for the first time, we construct a planar photovoltaic device based on MoS<sub>2</sub>/MoO<sub>3</sub>. By designing heterostructure and optimizing the thickness of the overlayer, the photoelectric performance of planar MoS<sub>2</sub>-based photovoltaic device is successfully improved, which provides a reference scheme for developing high-performance heterojunction photodetectors of MoS<sub>2</sub>/oxide materials in future.

A high-performance long-wave infrared photodetector based on a WSe2/PdSe2 broken-gap heterodiode.

Layered narrow bandgap quasi-two-dimensional (2D) transition metal dichalcogenides (TMDs) demonstrated excellent performance in long-wave infrared (LWIR) detection. However, the low light on/off ratio and specific detectivity (D*) due to the high dark current of the device fabricated using a single narrow bandgap material hindered its wide application. Herein, we report a type-III broken-gap band-alignment WSe2/PdSe2 van der Waals (vdW) heterostructure. The heterodiode device has a prominently low dark current and exhibits a high photoresponsivity (R) of 55.3 A W-1 and a high light on/off ratio >105 in the visible range. Notably, the WSe2/PdSe2 heterodiode shows an excellent uncooled LWIR response, with an R of ∼0.3 A W-1, a low noise equivalence power (NEP) of 4.5 × 10-11 W Hz-1/2, and a high D* of 1.8 × 108 cm Hz1/2 W-1. This work provides a new approach for designing high-performance room-temperature operational LWIR photodetectors.

An investigation into the hybrid architecture of Mn-Co nanoferrites incorporated into a polyaniline matrix for photoresponse studies.

In this study, an enhanced photoresponse was observed in the Mn-Co Nanoferrites (MCFs)-Polyaniline (PANI) nanohybrid architecture due to the formation of interface between PANI and MCFs, which provided a conduction pathway for the movement of charge carriers, and these interfaces were observed in a high-resolution transmission electron micrograph (HR-TEM). X-ray photoelectron spectroscopy (XPS) suggests that the carbon (C 1s) of the MCF-PANI nanohybrid shows peaks at 287.80 eV for CO, 286.17 eV for C-O, 285.24 eV for C-N, 284.50 eV for the sp3 hybridized carbon (C-C/C-H) and 283.84 eV for the sp2 hybridized carbon (CC). Current-voltage (I-V) curves reveal an ohmic nature of the MCF-PANI nanohybrid photodetector device. The photoresponse measurements were analyzed using the trap depth concept, demonstrating that the conductive polymer increases the photoconduction mechanism efficiency of MCFs. The constructed photodetector device exhibits a high photoresponsivity of 22.69 A W-1, a remarkable detectivity of 1.36 × 1012 cm Hz1/2 W-1 and a fast rise/decay time of 0.7/0.8 s. The excellent performance of the as-fabricated photodetector device could be explained by the intimate interaction between MCFs and PANI at their interface.

Homogeneous in-plane WSe2 P-N junctions for advanced optoelectronic devices.

Conventional doping schemes of silicon (Si) microelectronics are incompatible with atomically thick two-dimensional (2D) transition metal dichalcogenides (TMDCs), which makes it challenging to construct high-quality 2D homogeneous p-n junctions. Herein, we adopt a simple yet effective plasma-treated doping method to seamlessly construct a lateral 2D WSe2 p-n homojunction. WSe2 with ambipolar transport properties was exposed to O2 plasma to form WOx on the surface in a self-limiting process that induces hole doping in the underlying WSe2via electron transfer. Different electrical behaviors were observed between the as-exfoliated (ambipolar) region and the O2 plasma-treated (p-doped) region under electrostatic modulation of the back-gate bias (VBG), which produces a p-n in-plane homojunction. More importantly, a small contact resistance of 710 Ω μm with a p-doped region transistor mobility of ∼157 cm2 V-1 s-1 was achieved due to the transformation of Schottky contact into Ohmic contact after plasma treatment. This effectively avoids Fermi-level pinning and significantly improves the performance of photodetectors. The resultant WSe2 p-n junction device thus exhibits a high photoresponsivity of ∼7.1 × 104 mA W-1 and a superior external quantum efficiency of ∼228%. Also, the physical mechanism of charge transfer in the WSe2 p-n homojunction was analyzed. Our proposed strategy offers a powerful route to realize low contact resistance and high photoresponsivity in 2D TMDC-based optoelectronic devices, paving the way for next-generation atomic-thickness optoelectronics.

Enhancing Photoresponse and Photocurrent of Integrated Perovskite/Organic Solar Cells via Layer-by-Layer Processing

Perovskite solar cells have developed rapidly in recent years to almost rival silicon cells. To extend the photoresponse in the near-infrared region, integrated perovskite/organic solar cells (IPOSCs) have been developed. Typically, the organic bulk heterojunction (BHJ) in IPOSCs is built by one-step coating of a mixed solution of a donor and an acceptor. Here, we prepare the BHJ by layer-by-layer (LBL) processing. Compared to the traditional one-step coated IPOSCs (TOS device), the LBL-processed device (LBL device) exhibits a distinctly improved short-circuit current density (JSC) and power conversion efficiency. The TOS device shows a high photoresponse from about 400 to 900 nm, while the LBL device shows a high photoresponse extending to about 950 nm. Further research indicates that the extending photoresponse of the LBL-device is caused by the redshift of absorption of the organic BHJ. Meanwhile, the LBL-processed BHJ exhibits slightly improved carrier extraction and recombination. The introduction of LBL processing provides an approach to broaden the optical absorption range and photoresponse of IPOSCs.

Fabrication of freestanding GaN nanobelts with enhanced ultraviolet photoresponse performance

High-quality single component freestanding p-type and n-type GaN nanobelts were prepared by an electrochemical (EC) lift-off technique and subsequently transferred onto SiO2/Si substrates for the fabrication of high-performance ultraviolet photodetectors (UV PDs). The fabricated p-type nitrogen-polar (N-polar) GaN nanobelt UV PDs exhibited high photoresponsivity (7416.7 A/W) with a high photocurrent of 311 μA and the n-type devices presented high detectivity (1.44 × 1014 Jones) with a low dark current of 0.351 nA. Under dark condition, the thermionic field emission (TFE) and thermionic emission (TE) were found to be responsible for the current transport mechanisms of the p-type and n-type GaN nanobelt UV PDs, respectively. In addition, the enhancement of photoresponse performances in the N-polar GaN nanobelt PDs is not only attributed to their large surface-to-volume ratio but also to the strong built-in electric field. This work suggests that the rational combination of N-polar and surface effects of the freestanding GaN nanobelts is a viable approach to achieving high-performance GaN-based optoelectronic devices.

Flexible High‐Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

AbstractOptoelectronic performance of 2D transition metal dichalcogenides (TMDs)‐based solar cells and self‐powered photodetectors remain limited due to fabrication challenges, such as difficulty in doping TMDs to form p–n junctions. Herein, MoS2 diodes based on geometrically asymmetric contact areas are shown to achieve a high current rectification ratio of ≈105, facilitating efficient photovoltaic charge collection. Under solar illumination, the device demonstrates a high open‐circuit voltage (Voc) of 430 mV and a short‐circuit current density (Jsc) of −13.42 mA cm−2, resulting in a high photovoltaic power conversion efficiency (PCE) of 3.16%, the highest reported for a lateral 2D solar cell. The diodes also show a high photoresponsivity of 490.3 mA W−1, and a large photo detectivity of 4.05 × 1010 Jones, along with a fast response time of 0.8 ms under 450 nm wavelength at zero bias for self‐powered photodetection applications. The device transferred on a flexible substrate shows a high photocurrent and PCE retentions of 94.4%, and 88.2% after 5000 bending cycles at a bending radius of 1.5 cm, respectively, demonstrating robustness for flexible optoelectronic applications. The simple fabrication process, superior photovoltaic properties, and high flexibility suggests that the geometrically asymmetric MoS2 device architecture is an excellent candidate for flexible photovoltaic and optoelectronic applications.