Performance Of Photodetectors Research Articles

Enhanced SWIR Light Detection in Organic Semiconductor Photodetectors through Up-Conversion of Mid-Gap Trap States.

Shortwave-infrared (SWIR) photodetectors are vital for many scientific and industrial applications including surveillance, quality control and inspection. In recent decades, photodetectors based on organic semiconductors have emerged, demonstrating potential to add real value to broadband and narrowband imaging and sensing scenarios, where factors such as thermal budget sensitivity, large area aperture necessity, cost considerations, and lightweight and conformal flexibility demands are prioritized. It is now recognized that the performance of organic photodetectors (OPDs), notably their specific detectivity, is ultimately limited by trap states, universally present in disordered semiconductors. This work adopts an approach of utilizing these mid-gap states to specifically create a SWIR photo-response. To this end, this work introduces a somewhat counter-intuitive approach of "trap-doping" in bulk heterojunction (BHJs) photodiodes, where small quantities of a guest organic molecule are intentionally incorporated into a semiconducting donor:acceptor host system. Following this approach, this work demonstrates a proof-of-concept for a visible-to-SWIR broadband OPD, approaching (and, to some extent, even exceeding) state-of-the-art performance across critical photodetector metrics. The trap-doping approach is, even though only a proof-of-concept currently, broadly applicable to various spectral windows. It represents a new modality for engineering photodetection using the unconventional strategy of turning a limitation into a feature.

High‐Speed Short Infrared Detector Based on Vertical Gr/Se0.2Te0.8/GaAs Heterojunction

AbstractIn the domain of high‐performance short‐wave infrared (SWIR) photodetection and imaging, existing technologies predominantly utilize single‐crystal germanium and III‐V semiconductors. Despite their efficacy, these materials are encumbered by laborious synthesis and complex fabrication demands. In this study, the synthesis of large‐area, high‐crystallinity Se0.2Te0.8 thin films through a CMOS‐compatible vacuum thermal evaporation process is reported. A high‐speed, broad‐spectrum photodetector engineered with an innovative Gr/Se0.2Te0.8/GaAs vertical heterostructure is presented, which capitalizes on the augmented carrier mobility and employs graphene innovatively as both a carrier collection interface and an electrode. This configuration facilitates a remarkably swift response time of 800 ns/1 µs at the crucial 1310 nm wavelength for optical communications. Moreover, the fabrication of a 5 × 5 array device demonstrates substantial SWIR imaging capabilities at ambient conditions, marking a paradigm shift in uncooled infrared imaging and communication technologies. This work not only extends the boundaries of SWIR photodetector performance but also underscores the potential of novel material systems in high‐speed optical applications.

Rational synthesis of core/shell heterostructured quantum dots for improved self-powered photodetection performance enabled by energy band engineering

Colloidal quantum dots (CQDs), especially core-shell QDs, have attracted dramatic interests as emerging materials in optoelectronic devices due to their size tuneable band-gap, high absorption coefficient, facile and low-cost synthesis routing, etc. However, the precise design of core/shell band engineering along with charge carrier transfer efficiency are still challenging, inevitably impacting the performance of optoelectronic devices. Herein, three different types of CdSe/CdS core-shell heterostructured QDs have been obtained via a proposed synthesis strategy of adjusting the core size but fixing the shell thickness. The performance of the core-shell QDs based self-powered photodetectors can be efficiently regulated by the optimization of synthesis strategy with the design of energy band alignment. Compared to the quasi type-II and the type-I QDs devices, the Ilight/Idark ratio of type-II heterostructure based photodetector is increased by ∼2 and ∼5 orders of magnitude, respectively. The champion device exhibits extraordinary optoelectronic performance in terms of ultrahigh light-to-dark current ratio of 105, photoresponsivity of 10.64 mA/W, at bias of 0 V, respectively. The charge carrier dynamics and transfer mechanisms of the QDs were further investigated, revealing the improved carrier separation and transportation efficiency induced by a strong build-in electric field in type-II CdSe/CdS core-shell heterostructure. This work provides a new strategy for the next-generation self-powered QDs optoelectronics enabled by the proposed synthesis approach along with the design of energy band alignment.

Electrode materials and structures in UV photodetectors

Electrodes can be recognized as the bridges between photodetectors (PDs) and outer measurement circuits. The interfacial electric properties between electrodes and sensitive materials would dominate the separation and collection of photo-induced charge carrier, which are recognized as one of the critical factors influencing the photo-detecting performance. In this paper, the electrode materials used in UV PDs are summarized and categorized according to their components. Then, the effects of electrode configurations (such as the contact types, band structure, and electrode structure) on the photoelectric performances of UV PDs are discussed. Varied kinds of specific electrodes such as transparent electrodes, flexible electrodes, and bio-originated electrodes are described. Finally, the perspective of electrodes in UV PDs is presented, which provides guidance for their future development.

Precise arraying of perovskite single crystals through droplet-assisted self-alignment.

Patterned arrays of perovskite single crystals can avoid signal cross-talk in optoelectronic devices, while precise crystal distribution plays a crucial role in enhancing device performance and uniformity, optimizing photoelectric characteristics, and improving optical management. Here, we report a strategy of droplet-assisted self-alignment to precisely assemble the perovskite single-crystal arrays (PSCAs). High-quality single-crystal arrays of hybrid methylammonium lead bromide (MAPbBr3) and methylammonium lead chloride (MAPbCl3), and cesium lead bromide (CsPbBr3) can be precipitated under a formic acid vapor environment. The crystals floated within the suspended droplets undergo movement and rotation for precise alignment. The strategy allows us to deposit PSCAs with a pixel size range from 200 to 500 micrometers on diverse substrates, including indium tin oxide, glass, quartz, and poly(dimethylsiloxane), and the area can reach up to 10 centimeters by 10 centimeters. The PSCAs exhibit excellent photodetector performance with a large responsivity of 24 amperes per watt.

Precise arraying of perovskite single crystals through droplet-assisted self-alignment.

Patterned arrays of perovskite single crystals can avoid signal cross-talk in optoelectronic devices, while precise crystal distribution plays a crucial role in enhancing device performance and uniformity, optimizing photoelectric characteristics, and improving optical management. Here, we report a strategy of droplet-assisted self-alignment to precisely assemble the perovskite single-crystal arrays (PSCAs). High-quality single-crystal arrays of hybrid methylammonium lead bromide (MAPbBr3) and methylammonium lead chloride (MAPbCl3), and cesium lead bromide (CsPbBr3) can be precipitated under a formic acid vapor environment. The crystals floated within the suspended droplets undergo movement and rotation for precise alignment. The strategy allows us to deposit PSCAs with a pixel size range from 200 to 500 micrometers on diverse substrates, including indium tin oxide, glass, quartz, and poly(dimethylsiloxane), and the area can reach up to 10 centimeters by 10 centimeters. The PSCAs exhibit excellent photodetector performance with a large responsivity of 24 amperes per watt.

Highly-efficient low-cost polarization-sensitive organic photodetectors based on laminated self-assembly planar and bulk heterojunctions

To overcome the severe problems arising from the insufficient light absorption of ultrathin self-assembly active layers and the high cost use of atomic force deposition (ALD)-grown low-leakage-current transport layers, we successfully developed a low-cost, simple and facile strategy of floating-film transfer and multilayer lamination (FFTML) for constructing highly-efficient ALD-free broadband polarization-sensitive organic photodetectors (OPDs) with the two commonly used structures of donor/acceptor planar heterojunction (PHJ) and donor:acceptor multilayer bulk heterojunction (BHJ). It was found that the PHJ-based polarization-sensitive OPD by FFTML possesses a low dark current due to the high carrier injection barrier, indicating it is more suitable to be applied in low polarized light detection scenarios. In contrast, the BHJ-based device by FFTML has a higher spectral responsivity in the whole wavelength due to more photo-excitons transferred to the donor:acceptor interface and dissociated into photoexcited carrirers. Furthermore, the film thickness, which is tuned by increasing lamination number of BHJ layers, has a big effect on the polarization-sensitive photodetection performance. The polarization-sensitive 4-BHJ OPD by FFTML finally achieved a high specific detectivity of 8.33 × 1010 Jones, which was much higher than 2.72 × 1010 Jones for the 2-BHJ device at 0 V. This work demonstrates that layer-by-layer lamination of self-assembly films can effectively improve the polarized-light detection performance, contributing significantly to the rapid development of the field.

Sulfur-doped g-C3N4/GaN n-n heterojunction for high performance low-power blue-ultraviolet photodetector with ultra-high on/off ratio and detectivity

Polymeric graphitic carbon nitride (g-C3N4) shares a structural similarity to graphene, yet it possesses a distinctive electronic band structure, rendering it promising for photoelectric applications. However, g-C3N4 faces inherent limitations such as inadequate crystalline quality, limited conductivity, and a short lifespan of photogenerated charge carriers, all of which impede the photoelectric conversion efficiency. In this work, we introduce a two-step thermal vapor condensation method for depositing compact, crack-free sulfur-doped g-C3N4 thin films. The doped thin films exhibit reduced interlayer spacing, which leads to improved conductivity and charge transfer capabilities. These processes culminate in the creation of sulfur-doped g-C3N4/GaN thin film heterojunction blue-ultraviolet photodetectors with remarkable photodetection performance, including an ultrahigh on/off ratio of 7.3 × 107 and specific detectivity of 2.06 × 1014 Jones under a low bias of −0.4 V. Moreover, it is found that the n-n heterojunction undergoes a transition from photodiode to photoconduction behavior, attributed to the photoinduced electron trapping effects by sulfur-doped sites, which outcomes a notable gain with the responsivity as high as 581 mA/W. These findings underscore the vast potential of high-quality sulfur-doped g-C3N4 thin films for photoelectric applications.

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

Improving the Infrared Photodetector Performance of PbS Nanocrystal Superlattice through Ligand Optimization

Improving the Infrared Photodetector Performance of PbS Nanocrystal Superlattice through Ligand Optimization

Improving the Infrared Photodetector Performance of PbS Nanocrystal Superlattice through Ligand Optimization

Improving the Infrared Photodetector Performance of PbS Nanocrystal Superlattice through Ligand Optimization

Enhanced photothermoelectric conversion in self-rolled tellurium photodetector with geometry-induced energy localization

Photodetection has attracted significant attention for information transmission. While the implementation relies primarily on the photonic detectors, they are predominantly constrained by the intrinsic bandgap of active materials. On the other hand, photothermoelectric (PTE) detectors have garnered substantial research interest for their promising capabilities in broadband detection, owing to the self-driven photovoltages induced by the temperature differences. To get higher performances, it is crucial to localize light and heat energies for efficient conversion. However, there is limited research on the energy conversion in PTE detectors at micro/nano scale. In this study, we have achieved a two-order-of-magnitude enhancement in photovoltage responsivity in the self-rolled tubular tellurium (Te) photodetector with PTE effect. Under illumination, the tubular device demonstrates a maximum photovoltage responsivity of 252.13 V W−1 and a large detectivity of 1.48 × 1011Jones. We disclose the mechanism of the PTE conversion in the tubular structure with the assistance of theoretical simulation. In addition, the device exhibits excellent performances in wide-angle and polarization-dependent detection. This work presents an approach to remarkably improve the performance of photodetector by concentrating light and corresponding heat generated, and the proposed self-rolled devices thus hold remarkable promises for next-generation on-chip photodetection.

High performance of UV photodetectors by integration of plasmonic Ag nanoparticles on GaN

High-performance ultraviolet photodetectors have attracted much attention due to their various potential applications from household to universal. On basis of this, in this work, a high – performance and photoresponse enhancement UV photodetector based on Ag NPs/GaN heterojunction was demonstrated. By incorporating of Ag nanoparticles, light confinement determined by Ag nanostructure offers an effective approach to break through the limitation of the light-mater interaction within the photoactive layers of photodetector. Various size and elemental composition of Ag NPs are fabricated on GaN lead to significant enhancement of photocurrent in UV photodetector. Consequently, an outstanding photoresponsivity of 89 A/W, external quantum efficiency of 2.8 × 103% at low bias voltage of 0.3 V were achieved. The improve photo-response of the Ag NPs-decorated GaN-based photodetector is attributed to the simultaneous effect of strong plasmon absorption, increased injection of hot electrons into the conduction band of GaN. This study will open up the direction to fabricate the high-performance UV photodetector.

Enhancement of the response speed of CIGS-based photodetector by Te-doping

Cu(In,Ga)Se2 (CIGS) based devices are promising candidates for high performance photodetector applications. The present work investigated the effects of Te-doping on the properties of CIGS layers and studied the performance of photodetectors (PDs) fabricated on these films. The films were vacuum evaporated on glass substrates and their morphological, structural and optical properties were evaluated after an annealing step at 550ºC. Morphological data indicated that undoped CIGS films had non-uniform surface features with large grains separated by nanoparticles. Addition of 6.6 % Te improved the morphology and yielded a smoother layer. Further increase in Te concentration showed appreciable reduction in surface feature size and shape. X-ray diffraction patterns showed that increasing the Te amount in CIGS caused a shift in the XRD peaks towards smaller angles pointing to replacement of Se atoms by Te. Peak splitting at higher Te samples suggested a graded structure with Se and Te amounts changing through the thickness of the film. Raman analysis demonstrated formation of CuInGa(Se,Te)2 (CIGST) compound. According to Tauc’s approximation, CIGS films with and without Te atoms possessed two energy band gaps of Eg1 and Eg2 that were in the ranges of 1.10–1.28 eV and 1.16–1.36 eV, respectively. Electrical data obtained from photodetector devices showed a responsivity of 4.44×10−1 A/W and a detectivity of 8.01×107 Jones for Te-free material, while the rise/fall times were measured as 34/148 ms. A much faster response speed of 19/20 ms was reached for devices fabricated on films with 10.2 % Te. This work demonstrated, for the first time, the fabrication low-cost and high-performance metal-semiconductor-metal (MSM) type CIGST-based PDs.

Optimizing Photoelectrochemical UV Imaging Photodetection: Construction of Anatase/Rutile Heterophase Homojunctions and Oxygen Vacancies Engineering in MOF-Derived TiO2.

Self-powered photoelectrochemical (PEC) ultraviolet photodetectors (UVPDs) are promising for next-generation energy-saving and highly integrated optoelectronic systems. Constructing a heterojunction is an effective strategy to increase the photodetection performance of PEC UVPDs because it can promote the separation and transfer of photogenerated carriers. However, both crystal defects and lattice mismatch lead to deteriorated device performance. Here, we introduce a structural regulation strategy to prepare TiO2 anatase-rutile heterophase homojunctions (A-R HHs) with oxygen vacancies (OVs) photoanodes through an in situ topological transformation of titanium metal-organic framework (Ti-MOF) by pyrolysis treatment. The cooperative interaction between A-R HHs and OVs suppresses carrier recombination and accelerates carrier transport, thereby significantly enhancing the photodetection performance of PEC UVPDs. The obtained device realizes a high on/off ratio of 10,752, a remarkable responsivity of 24.15 mA W-1, an impressive detectivity of 3.28 × 1011 Jones, and excellent cycling stability. More importantly, under 365 nm light illumination, a high-resolution image of "HUST" (the abbreviation of Harbin University of Science and Technology) was obtained perfectly, confirming the excellent optical imaging capability of the device. This research not only presents an advanced methodology for constructing TiO2-based PEC UVPDs, but also provides strategic guidance for enhancing their performance and practical applications.

Organic Visible‐Blind Ultraviolet Photodiodes and Pixel‐Array Imagers Based on [1]Benzothieno[3,2‐b]Benzothiophene (BTBT) Derivatives

AbstractVisible‐blind ultraviolet (VBUV) photodetectors are designed for UV detection without responding to visible light, thus having many applications in communications, flame detection, environment monitoring, and astronomy. Herein, an organic device concept based on the bulk heterojunction (BHJ) photodiode is presented for high‐performance VBUV photodetection and imaging. The BHJ, comprised of an organic electron donor, 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT), and an electron acceptor, indene‐C60 bisadduct (ICBA), shows efficient generation and transport of free charges upon UV irradiation. The organic photodiode (OPD) delivers exceptional VBUV photodetection performance. At a low voltage of −0.5 V, the device exhibits a wide linear dynamic range of 98.15 dB. Furthermore, the OPD can detect ultra‐low light intensities down to 0.58 µW cm−2 with a high photoresponsivity of 0.12 A W−1 and specific detectivity of 2.75 × 1012 Jones. More importantly, by integrating the OPD with a readout integrated circuit, the pixel‐array organic VBUV imager is demonstrated to have high‐quality imaging capability. The results reveal a novel strategy to design VBUV photodetectors and imagers with balanced performance, cost, area, flexibility, and power consumption.

Enhancement of Photodetector Characteristics by Zn-Porphyrin-Passivated MAPbBr3 Single Crystals.

Perovskite single crystals have garnered significant interest in photodetector applications due to their exceptional optoelectronic properties. The outstanding crystalline quality of these materials further enhances their potential for efficient charge transport, making them promising candidates for next-generation photodetector devices. This article reports the synthesis of methyl ammonium lead bromide (MAPbBr3) perovskite single crystal (SC) via the inverse-temperature crystallization method. To further improve the performance of the photodetector, Zn-porphyrin (Zn-PP) was used as a passivating agent during the growth of SC. The optical characterization confirmed the enhancement of optical properties with Zn-PP passivation. On single-crystal surfaces, integrated photodetectors are fabricated, and their photodetection performances are evaluated. The results show that the single-crystalline photodetector passivated with 0.05% Zn-PP enhanced photodetection properties and rapid response speed. The photoelectric performance of the device, including its responsivity (R), external quantum efficiency (EQE), detective nature (D), and noise-equivalent power (NEP), showed an enhancement of the un-passivated devices. This development introduces a new potential to employ high-quality perovskite single-crystal-based devices for more advanced optoelectronics.

Lewis Acid-Doped Transition Metal Dichalcogenides for Ultraviolet-Visible Photodetectors

Abstract Ultraviolet photodetectors (UV PDs) are widely used in civilian, scientific, and military fields due to their high sensitivity and low false alarm rates. This paper has presented a temperature-dependent Lewis acid p-type doping method for transition metal dichalcogenides (TMDs), which effectively extended the optical response range. The p-type doping based on surface charge transfer involved the chemical adsorption of the Lewis acid SnCl4 as a light absorption layer on the surface of WS2, significantly enhancing its UV photodetection performance. Under 365 nm laser irradiation, WS2 PDs exhibited a response speed of 24 ms/20 ms, a responsivity of 660 mA/W, a detectivity of 3.3×1011 Jones, and an external quantum efficiency of 226%. Moreover, we successfully applied this doping method to other TMDs materials (such as MoS2, MoSe2, and WSe2) and fabricated WS2 lateral p-n heterojunction PDs.

Rational design of comb-like 1D-1D ZnO-ZnSe heterostructures toward their excellent performance in flexible photodetectors.

One-dimensional (1D) Zn-based heterostructures have attracted considerable interest in the field of photodetection because of their tunable properties, flexibility, and unique optoelectronic properties. However, designing 1D multi-component Zn-based heterostructures for advanced photodetectors is still a great challenge. Herein, comb-like 1D-1D ZnO-ZnSe heterostructures with ZnO and ZnSe nanowires (NWs) comprising the shaft and teeth of a comb are reported. The length of the ZnO NWs can be modulated in the range of 300-1200 nm. Microstructural characterizations confirm that the 1D heterostructure clearly shows the spatial distribution of individual components. The well-designed structure displays an extended broadband photoresponse and higher photosensitivity than pure ZnSe NWs. Furthermore, ZnSe NWs with an appropriate length of ZnO branches show increased photoresponses of 3835% and 798% compared to those of pure ZnSe NWs under green and red-light irradiation, respectively. In addition, the integrated flexible photodetector presents excellent folding endurance after 1000 bending tests. This well-designed structure has significant potential for other 1D-based semiconductors in optoelectronic applications.