High-performance Photodetectors Research Articles

Enhanced DFT predictions of the structural and optoelectronic properties of MoTe2 for high performance photodetection: Application to GW-based functionals and Hubbard U and V corrections

Molybdenum ditelluride (MoTe2) is a promising two-dimensional material with ultimate prospective usage in high performance photodetection devices. In this study, we elucidate how this may be revealed and discuss how structural and optoelectronic properties of MoTe2 can be numerically accurately simulated since earlier experimental and theoretical studies on the bandgap of MoTe2 produced contradictory findings. In doing so, GW-based functionals using Hubbard U and V corrections are included in density functional theory (DFT) calculations to improve bandgap estimations. Interestingly, we reliably demonstrated that the estimated values of the bandgaps of 0.83 eV and 0.73 eV obtained, respectively, within this framework of DFT+U+V and GW, perfectly match the reported experimental results. Specifically, the quantum espresso simulation package is used for accurate DFT calculations allowing thereby a comprehensive investigation of the impact of the Hubbard U correction on the bandgap of MoTe2. Additionally, the optical absorption spectrum is examined for both GW and RPA levels of theory using the Yambo simulation tool, allowing for a readily distinctly identification of the material’s light absorption spectrum. Contrasted by previous theoretical results, the random phase approximation (RPA) approach, which performs quite well in showing increased optical efficiency, reveals its effectiveness for obtaining appreciable gains in the values of the real, imaginary, refractive index, and extinction coefficient. The expected trends obtained with GW-based functionals using Hubbard U and V corrections approximate methods are encouraging, and altogether support ongoing attempts to optimize the physical properties of MoTe2 for high-performance photodetection systems by offering more precise bandgap predictions and valuable insights related particularly to the optical properties.

Improved performance and stability in CH3NH3PbI3/Si heterojunction photodetectors realized by ZIF-67 additive assisted Co ion doping

Lead halide perovskites have been regarded as promising materials for fabrication of high-performance photodetectors (PDs). However, spin-coated perovskite thin films generally have suffered from high-density grain boundaries and defect states, which severely deteriorated the performance and stability of resulting PDs. Fortunately, the above issues can be effectively solved via additive assisted metal ions doping. In this work, Co-based zeolite imidazole framework (ZIF-67) additive assisted Co ion doping has been proposed to prepare high-quality perovskite CH3NH3PbI3 (MAPbI3) thin films. Morphological, structural, optical, and electrical studies have shown that Co ion doping decreased grain boundaries as well as suppressed defect states, which greatly enhanced the performance and stability of MAPbI3/Si heterojunction PDs, including reducing dark current, increasing photocurrent, and increasing response speed. Finally, the mechanisms of suppression of defect states benefiting from Co ion doping were discussed based on density functional theory calculations. The results provided in this work will pave the way for development of high-performance and stable MAPbI3 PDs in the future.

High-performance UV light detector using layered perovskites and textured silicon heterojunction

UV photodetectors have gained popularity due to their high precision and capability to filter out interference from solar electromagnetic radiation. A UV detector of (BA)2PbCl4/textured silicon (BA = n-butylammonium) heterojunction was fabricated by depositing (BA)2PbCl4 thin film on textured silicon. High performances of a rapid UV light response (trise = tfall = 0.24 s), high responsivity (8.16 mA/W), and a low detection limit (7.5 μW/cm2) were obtained from the designed detector, which were ascribed the unique morphology and structure of the detector. The rough surface morphology of textured silicon enlarges the light-absorbing area of (BA)2PbCl4 by 20 times. Moreover, a p-n junction was constructed between (BA)2PbCl4 and textured silicon. The electric field naturally present in the heterojunction facilitates the transport of carriers. Furthermore, the (BA)2PbCl4/textured silicon heterojunction exhibited significant selectivity towards UV light and demonstrated remarkable stability and repeatability in the air environment. This work offers a new strategy for developing inexpensive and high-performance UV photodetectors, which is significant for exploring the potential of layered perovskites in new photodetector device applications.

Effect of oxygen pressure during the growth of ZnSnO3 epitaxial thin films on LiNbO3 substrates

High-quality ZnSnO3 epitaxial films are grown on LiNbO3(0001) substrates by pulsed laser deposition in an oxygen pressure range of 0.1–10 Pa. The crystalline quality, composition, surface topography, structure, defect formation energy and photovoltaic properties of the epitaxial films are found to be highly sensitive to change in the oxygen pressure by experiments and first-principles density functional theory (DFT). The epitaxial relationship between the film and the substrate is identified as ZnSnO3(0001) || LiNbO3(0001) with ZnSnO3 [2¯ 110] || LiNbO3[2¯ 110]. The film grown atPO2 = 10 Pa has the highest crystal quality, but the photodetector based on the film obtained atPO2 = 0.1 Pa presents the highest responsivity (2.24 A/W at 1 V) and light/dark current ratio (∼105 at 1 V) under the 254-nm-light irradiation. Our results indicate that the as-grown ZnSnO3 epitaxial film should be a potential material for fabricating high-performance UV photodetectors.

Highly Efficient Van Der Waals Heterojunction on Graphdiyne toward the High-Performance Photodetector.

Graphdiyne (GDY), a new 2D material, has recently proven excellent performance in photodetector applications due toits direct bandgap and high mobility. Different from the zero-gap of graphene, these preeminent properties made GDY emerge as a rising star for solving the bottleneck of graphene-based inefficient heterojunction. Herein, a highly effective graphdiyne/molybdenum (GDY/MoS2 ) type-II heterojunction in a charge separation is reported toward a high-performance photodetector. Characterized by robust electron repulsion of alkyne-rich skeleton, the GDY based junction facilitates the effective electron-hole pairs separation and transfer. This results in significant suppression of Auger recombination up to six times at the GDY/MoS2 interface compared with the pristine materials owing to an ultrafast hot hole transfer from MoS2 to GDY. GDY/MoS2 device demonstrates notable photovoltaic behavior with a short-circuit current of -1.3 × 10-5 A and a large open-circuit voltage of 0.23V under visible irradiation. As a positive-charge-attracting magnet, under illumination, alkyne-rich framework induces positive photogating effect on the neighboring MoS2 , further enhancing photocurrent. Consequently, the device exhibits broadband detection (453-1064nm) with a maximum responsivity of 78.5 A W-1 and a high speed of 50 µs. Results open up a new promising strategy using GDY toward effective junction for future optoelectronic applications.

Photovoltaic high-performance broadband photodetector based on the heterojunction of MoS2/silicon nanopillar arrays

Two-dimensional MoS2 has shown great potential in the photoelectric field because of its excellent optical and electrical properties. However, the performance of MoS2-based planar photodetector is constrained by the short transmission path and limited light absorption capacity of the planar thin layer of MoS2. In this paper, highly sensitive MoS2/silicon nanopillar arrays(Si-NPAs) photodetector by coating the surface of silicon nanotrap light array with MoS2. The interaction between light waves and silicon nanopillars and MoS2 is significantly enhanced by the Fabry-Pérot-enhanced Mie resonance between pillars as well as the multiple reflection. In the meantime, a Van der Waals heterojunction is constructed between the MoS2 and Si-NPAs coated across a large area. This is beneficial to address the poor performance of traditional two-dimensional photodetectors in light absorption and prevent the surface recombination of silicon-based photodetectors. According to the research results,the detector has 4.15 × 102 excellent rectification characteristics and 1.93 × 103 high switch ratio, and the photovoltaic effect is significant. The average external quantum efficiency of MoS2/Si-NPAs photodetector is 61.2% in the visible and near infrared bands, which is twice that of MoS2/planar silicon photodetector. At 850 nm, the responsiveness of the MoS2/Si NPAs photodetector is 0.48 A/W. the detection rate reaches 1.058 × 1012cm·Hz 1/2 W−1, which is 10.7 times higher than that of MoS2/planar silicon photodetector. To sum up, this study contributes a fresh idea to the design and application of high-performance devices.

Reverse-distribution phase featured gradient heterojunction: A universal strategy to realize high-performance near-infrared organic photodetectors for real-time arterial monitoring

Near-infrared (NIR) organic photodetectors (OPDs) play significant roles in night vision, optical communication and bio-imaging for low cost, easy fabrication and flexibility. However, their development is facing a serious challenge that efforts on suppressing typically high dark current density (JD) generally encounter photoresponse loss because of accompanying with less exciton generation or poorer carrier extraction. Here, novel structure and mechanism are pioneered to overcome that challenge: forming a reverse-distribution phase featured gradient heterojunction (RP-GHJ) to build an effective charge transport channel. In such structure, increased barriers are established to prevent unfavorable charge injection for suppressing JD. Additionally, photogenerated carriers are wrapped by anti-recombination region in reverse phase for efficient charge extraction. Therefore, RP-GHJ suppresses JD of NIR-OPDs to 8.48 × 10−9 A cm−2 which is far superior to 1.81 × 10−6 A cm−2 of traditional BHJ one (bias of −1 V) and simultaneously keeps high photoresponse. Consequently, RP-GHJ makes NIR-OPD realize stable-high detectivity over 1013 Jones at bias region from 0 to − 0.5 V and when the bias increases from − 0.5 to − 1 V, decrease of specific detectivity is slight (under 830 nm). And more importantly, a very large linear dynamic range of nearly 160 dB is obtained under 0 V bias. The structure is proven to be universally effective in NIR-OPDs and a highly sensitive arterial pulse monitoring is developed. The novel structure and mechanism provide a universal strategy for realizing high-performance NIR-OPDs and their real applications.

High responsivity and multi-wavelength response photodetector based on single bandgap AlInN film by magnetron sputtering

The AlInN film with a band gap of 2.96 eV is prepared on glass by radio frequency magnetron sputtering. Photoluminescence spectra reveals that the emission band is originated from both the band-edge and some defect-related radiation. The interdigital AlInN photodetector based on metal−semiconductor−metal (MSM) structure exhibits photoresponse characteristics from ultraviolet to visible light. The defect energy level is responsible for the multi-wavelength response of the low-energy incident irradiation light. The photodetector exhibits the best performance under 660 nm illumination, with a responsivity of 102 A/W, an external quantum efficiency of 190% and a specific detectivity of 2.8 × 109 Jones. These three factors improve by 4–6 orders of magnitude compared to point electrodes. The AlInN MSM interdigital electrode structure provides a relatively promising candidate structure for achieving high-performance multi-wavelength photodetectors.

Regulating 3D Phase in Quasi-2D Perovskite Films for High-Performance and Stable Photodetectors.

The charge transport in quasi-2D perovskites limits their applications despite the superior stability and optoelectronic properties. Herein, a novel strategy is proposed to enhance the charge transport by regulating 3D perovskite phase in quasi-2D perovskite films. The carbohydrazide (CBH) as an additive is introduced into (PEA)2 MA3 Pb4 I13 precursors, which slows down the crystallization process and improves the phase ratio and crystal quality of the 3D phase. This structure change results in a significant improvement in charge transport and extraction, leading to the device demonstrating an almost 100% internal quantum efficiency, a peak responsivity of 0.41AW-1 , and a detectivity of 1.31×1012 Jones at 570nm under 0V bias. Furthermore, the air and moisture stability of (PEA)2 MA3 Pb4 I13 films is not deteriorated but gets significantly improved due to the better crystal quality and the passivation of defects by the residual CBH molecule. This work demonstrates a strategy for improving the charge transport properties of quasi-2D perovskites and also sheds light on solving the stability issue of 3D perovskite films via the proper passivation or additives, which will inspire the fast development of the perovskite community.

High-performance broadband flexible photodetector based on Gd3Fe5O12-assisted double van der Waals heterojunctions

Flexible photodetectors are fundamental components for developing wearable systems, which can be widely used for medical detection, environmental monitoring and flexible imaging. However, compared with 3D materials, low-dimensional materials have degraded performance, a key challenge for current flexible photodetectors. Here, a high-performance broadband photodetector has been proposed and fabricated. By combining the high mobility of graphene (Gr) with the strong light–matter interactions of single-walled carbon nanotubes (SWCNTs) and molybdenum disulfide (MoS2), the flexible photodetector exhibits a greatly improved photoresponse covering the visible to near-infrared range. Additionally, a thin layer of gadolinium iron garnet (Gd3Fe5O12, GdlG) film is introduced to improve the interface of the double van der Waals heterojunctions to reduce the dark current. The SWCNT/GdIG/Gr/GdIG/MoS2 flexible photodetector exhibits a high photoresponsivity of 47.375 A/W and a high detectivity of 1.952 × 1012 Jones at 450 nm, a high photoresponsivity of 109.311 A/W and a high detectivity of 4.504 × 1012 Jones at 1080 nm, and good mechanical stability at room temperature. This work demonstrates the good capacity of GdIG-assisted double van der Waals heterojunctions on flexible substrates and provides a new solution for constructing high-performance flexible photodetectors.

Improved Perovskite CH3NH3PbI3 Thin Films by ZIF‐67 Additive Assisted Co Ion Doping toward High‐Performance and Stable Photodetectors

AbstractLead halide perovskites are considered important materials for the fabrication of high‐performance optoelectronic devices. However, the poor quality of thin films with abundant grain boundaries and defect states greatly lower the performance and stability of as‐fabricated devices. In the present work, the growth of improved perovskite CH3NH3PbI3 thin films through Co‐based zeolite imidazole framework (ZIF‐67) additive assisted Co ion doping is reported. Investigation of the morphological, structural, optical, and electrical properties shows that the Co ion doped CH3NH3PbI3 (CH3NH3Pb0.98Co0.02I3) thin films exhibit low grain boundaries, low defect states, and improved structural stabilities. The positive roles of suppression of defect states are further demonstrated by improved performance and stability of photodetectors based on CH3NH3Pb0.98Co0.02I3 thin films. Finally, density functional theory calculations are performed to reveal the mechanisms of passivation of undercoordinate Pb2+ vacancy defect states by Co ion doping. The results provided in this work will pave the way toward the fabrication of high performance and stable perovskite photodetectors in the future.

Surface plasmon assisted high-performance photodetectors based on hybrid TiO2@GaOxNy-Ag heterostructure

In this work, we reported a high-performance-based ultraviolet-visible (UV-VIS) photodetector based on a TiO2@GaOxNy-Ag heterostructure. Ag particles were introduced into TiO2@GaOxNy to enhance the visible light detection performance of the heterojunction device. At 380 nm, the responsivity and detectivity of TiO2@GaOxNy-Ag were 0.94 A/W and 4.79 × 109 Jones, respectively, and they increased to 2.86 A/W and 7.96 × 1010 Jones at 580 nm. The rise and fall times of the response were 0.19/0.23 and 0.50/0.57 s, respectively. Uniquely, at 580 nm, the responsivity of fabricated devices is one to four orders of magnitude higher than that of the photodetectors based on TiO2, Ga2O3, and other heterojunctions. The excellent optoelectronic characteristics of the TiO2@GaOxNy-Ag heterojunction device could be mainly attributed to the synergistic effect of the type-Ⅱ band structure of the metal–semiconductor–metal heterojunction and the plasmon resonance effect of Ag, which not only effectively promotes the separation of photogenerated carriers but also reduces the recombination rate. It is further illuminated by finite difference time domain method (FDTD) simulation and photoelectric measurements. The TiO2@GaOxNy-Ag arrays with high-efficiency detection are suitable candidates for applications in energy-saving communication, imaging, and sensing networks.

Fast Evaluation of RF Power Spectrum of Photodetectors With Windowing Functions

Time window functions are used as broadband excitations to obtain the output power spectrum of photodetectors. Numerical results show a good agreement with experimental results. The proposed method yields a two-orders-of-magnitude reduction in computing time and memory compared to traditional monochromatic calculations. This large reduction makes it possible to design high-performance photodetectors with numerical optimization on desktop computers. We use this approach to design a device whose 3-dB bandwidth is four times larger than the initial design.

High-performance ultraviolet photodetector based on Sn-doped CuO@ZnO nanorod arrays composites

The Sn-doped CuO nanosheets were synthesized on the surface of ZnO nanorods arrays by a two-step method. The as-prepared samples were investigated by X-ray diffraction (XRD), electron microscopy techniques (SEM and EDS), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and evaluation of photoelectric performances. With the increase of [Sn4+]/[Cu2+] concentration ratio, the size and number of CuO nanosheets coated on the surface of ZnO nanorods become smaller, and the surface of ZnO nanorods become more and more rough. When the [Sn4+]/[Cu2+] concentration ratio is 2%, the dark current, photocurrent and photoelectric sensitivity of the prepared Sn-doped CuO@ZnO nanorod arrays composites photoelectric devices are 0.038 µA, 141.52 µA and 3724.2, respectively. In this sense, probing the Sn modified CuO@ZnO nanorod arrays composites can elucidate some useful keys for the development of high photoelectric properties.

Self-powered broadband photodetector based on Bi2Se3/GaN pn mixed-dimensional heterojunction with boosted responsivity

Self-powered broadband photodetectors (SPBDs) have received considerable attention because of their significance in optoelectronic applications. However, limited by problems inherent to the material, such as high dislocation density, complex heteroepitaxy processing of bulk materials, and the small photoabsorption cross section in atomically thin layers of two-dimensional materials, SPBD photodetectors with both a wide detection range and attractive response characteristics are difficult to fabricate. To address this difficulty, herein the synthesis of n-Bi2Se3/p-GaN mixed-dimensional heterojunctions by the transfer method and their assembly into SPBD photodetectors are described. This photodetector offers both a wide spectral response range (ultraviolet to mid-infrared) and excellent response characteristics. The high responsivity (24554 A/W, 3V), remarkable Ion/Ioff (223.8), and rapid rise and decay times (τr = 0.063 s and τd = 0.043 s) benefit from both the built-in electric field of the pn junction and the fast electron transport on the surface of topological insulator Bi2Se3. The results of this research should facilitate the use of this emerging material for the design and fabrication of high-performance SPBD photodetectors.

Interface engineering SnS2/MXene Nb2C self-powered photodetectors with high responsivity and detectivity

Research on two-dimensional (2D) materials and their van der Waals heterostructures (vdWHs) has generated a lot of interest in the fields of electronics and optoelectronics. However, the construction of 2D heterostructures remains a challenge because the most widely used deterministic placement method to perform 2D layer stacking often suffers from erratic control of lattice orientation over lattice orientations. Herein, a new 2D/2D SnS2/MXene Nb2C heterostructure for high-performance photodetectors (PDs) was designed and prepared by using a simple electrostatic assembly process. It was demonstrated that the combination of Nb2C MXene nanosheets (NSs) and SnS2 NSs significantly improved the performance of PDs by enhancing the charge transfer, carrier density, light adsorption, as well as by decreasing band bending edge and charge recombination. The SnS2/Nb2C PDs exhibited remarkable responsivity (102.44 μA/W) and ultrahigh specific detectivity (7.48 × 1012 Jones) at zero external bias under a 365 nm laser at level Ⅳ. Additionally, comprehensive investigations of energy level diagram derived from both experimental measurements and density functional theory calculations provided further insights of such photodetector system. This simple and reliable fabrication strategy opens a new avenue for the large-scale production of low-cost and high-quality MXenes-based heterogeneous bond for next-generation electronic and optoelectronic applications.

High Performance GaN-Based Ultraviolet Photodetector via Te/Metal Electrodes.

Photodetectors (PDs) based on two-dimensional (2D) materials have promising applications in modern electronics and optoelectronics. However, due to the intralayer recombination of the photogenerated carriers and the inevitable surface trapping stages of the constituent layers, the PDs based on 2D materials usually suffer from low responsivity and poor response speed. In this work, a distinguished GaN-based photodetector is constructed on a sapphire substrate with Te/metal electrodes. Due to the metal-like properties of tellurium, the band bending at the interface between Te and GaN generates an inherent electric field, which greatly reduces the carrier transport barrier and promotes the photoresponse of GaN. This Te-enhanced GaN-based PD show a promising responsivity of 4951 mA/W, detectivity of 1.79 × 1014 Jones, and an external quantum efficiency of 169%. In addition, owing to the collection efficiency of carriers by this Te-GaN interface, the response time is greatly decreased compared with pure GaN PDs. This high performance can be attributed to the fact that Te reduces the contact resistance of the metal electrode Au/Ti to GaN, forming an ohmic-like contact and promoting the photoresponse of GaN. This work greatly extends the application potential of GaN in the field of high-performance photodetectors and puts forward a new way of developing high performance photodetectors.

Lead-Free Halide Double Perovskite for High-Performance Photodetectors: Progress and Perspective.

Lead halide perovskite has become a promising candidate for high-performance photodetectors (PDs) due to its attractive optical and electrical properties, such as high optical absorption coefficient, high carrier mobility, and long carrier diffusion length. However, the presence of highly toxic lead in these devices has limited their practical applications and even hindered their progress toward commercialization. Therefore, the scientific community has been committed to searching for low-toxic and stable perovskite-type alternative materials. Lead-free double perovskite, which is still in the preliminary stage of exploration, has achieved inspiring results in recent years. In this review, we mainly focus on two types of lead-free double perovskite based on different Pb substitution strategies, including A2M(I)M(III)X6 and A2M(IV)X6. We review the research progress and prospects of lead-free double perovskite photodetectors in the past three years. More importantly, from the perspective of optimizing the inherent defects in materials and improving device performance, we propose some feasible pathways and make an encouraging perspective for the future development of lead-free double perovskite photodetectors.

High performance ultraviolet photodetector based on CsPbCl3/ ZTO heterostructure film enabled by effective separation of photocarriers

Ultraviolet photodetectors have gained attention due to their wide range of applications. All-inorganic perovskite, especially CsPbCl3, has become a promising ultraviolet photoelectric detecting material in recent years due to its suitable band gap and excellent optical properties. However, because of the low solubility of CsCl in traditional organic solvents, the CsPbCl3 film quality is poor and its detection performance is limited to improve. During this work, we fabricated a high performance ultraviolet photodetectors based on CsPbCl3/ Zn2SnO4 heterostructure film. The introduction of Zn2SnO4 not only improves the quality of CsPbCl3 films, but also allows the interface charge of CsPbCl3 to be effectively separated. Under the dual action of heterostructure film, the on/ off switching ratio and responsivity of the device are increased by two and one orders of magnitude. In addition, we have successfully manufactured flexible ultraviolet photodetectors based on CsPbCl3/ Zn2SnO4 heterostructure film, and the devices have demonstrated excellent performance on flexible substrates. This work shows that CsPbCl3/ Zn2SnO4 heterostructure film have broad application prospects in the construction of high-performance ultraviolet photodetectors and other photovoltaic devices.

Self-powered photodetectors based on Er-doped MoS2 film for NIR photo-communication and laser calibration

Molybdenum disulfide (MoS2) is a promising two-dimensional material for optoelectronic applications owing to its strong light–matter interactions, high carrier mobility, and ability to combine with other materials. However, the intrinsic bandgap (1.3–1.8 eV) of MoS2 limits its applications in the near-infrared (NIR) region. Herein, a heterojunction NIR photodetector based on the Er-doped MoS2 film is developed. The photodetector presents self-powered NIR response with a fast rise/fall time of ∼9.2 μs/∼168 μs and a high detectivity of ∼3.25 × 1010 Jones at 980 nm. The high performance of the device is attributed to the improved separation of the photogenerated electron–hole pairs and the characteristic trapping capacity induced by Er dopants. Density functional theory calculations reveal that Er-doping introduces an additional energy level in the forbidden band of the MoS2:Er, and the Er-f electron orbital locates near its Fermi energy level, both of which contribute to the formation of photogenerated carriers. The MoS2:Er-based device with a 3-dB bandwidth of 5.4 kHz exhibits promising application potential in the NIR photo-communication field. Moreover, the laser calibration application of the high-performance photodetector is demonstrated. This work not only develops an effective strategy to enhance the NIR photoresponse of MoS2 films but also extends the application of MoS2-based devices.