Dichroic Ratio Research Articles

Single Ether‐Based Side Chains in Conjugated Polymers: Toward Power Factors of 2.9 mW m−1 K−2

AbstractCombining side chain engineering and controlled alignment of PBTTT is an effective strategy to produce oriented thin films with improved thermoelectric performance when doped sequentially with the acceptor molecule hexafluoro‐tetracyanonaphthoquinodimethane (F6TCNNQ). The substitution of linear alkyl side‐chains (n‐C12) with a chain of identical length including an ether function (n‐C7OC4) leads to a new class of slightly polar PBTTT polymers, preserving the ease of synthesis and air stability of alkylated PBTTTs. This side‐chain modification improves the structural order of PBTTT backbones and the thermo‐mechanical properties of the polymer. It then can be oriented by high temperature rubbing up to 240 °C to reach very high dichroic ratios up to 20 thanks to enhanced cohesive forces within side‐chain layers. The side chain polarity of n‐C7OC4 helps to tune the polymer‐dopant interactions. A multi‐technique approach demonstrates that F6TCNNQ dopants are randomly oriented in the disordered side chain layers of n‐C7OC4 with some evidence of dopant clustering. The combination of improved alignment and random orientation of intercalated F6TCNNQ dopants helps reach a very high charge conductivity σ = 5 ⋅ 104 S cm−1 and a record power factor of 2.9 mW m−1 K−2 in the polymer chain direction.

Polarimetric Image Sensor and Fermi Level Shifting Induced Multichannel Transition Based on 2D PdPS.

2D materials have been attracting high interest in recent years due to their low structural symmetry, excellent photoresponse, and high air stability. However, most 2D materials can only respond to specific light, which limits the development of wide-spectrum photodetectors. Proper bandgap and the regulation of Fermi level are the foundations for realizing electronic multichannel transition, which is an effective method to achieve a wide spectral response. Herein, a noble 2D material, palladium phosphide sulfide (PdPS), is designed and synthesized. The bandgap of PdPS is around 2.1eV and the formation of S vacancies, interstitial Pd and P atoms promote the Fermi level very close to the conduction band. Therefore, the PdPS-based photodetector shows impressive wide spectral response from solar-blind ultraviolet to near-infrared based on the multichannel transition. It also exhibits superior optoelectrical properties with photoresponsivity (R) of 1 × 103 A W-1 and detectivity (D*) of 4 × 1011 Jones at 532nm. Moreover, PdPS exhibits good performance of polarization detection with dichroic ratio of ≈3.7 at 808nm. Significantly, it achieves polarimetric imaging and hidden-target detection in complex environments through active detection.

Ultra‐High Alignment of Polymer Semiconductor Blends Enabling Photodetectors with Exceptional Polarization Sensitivity

AbstractPhotodetectors that can sense not only light intensity but also light's polarization state add valuable information that is beneficial in a wide array of applications. Polymer semiconductors are an attractive material system to achieve intrinsic polarization sensitivity due to their anisotropic optoelectronic properties. In this report, the thermomechanical properties of the polymer semiconductors PBnDT‐FTAZ and P(NDI2OD‐T2) are leveraged to realize bulk heterojunction (BHJ) films with record in‐plane alignment. Two polymer blends with distinct weight average molar masses (Mw) are considered and either a strain‐ or rub‐alignment process is applied to align the polymer blend films. Optimized processing yields films with dichroic ratios (DR) of over 11 for the high Mw system and nearly 17 for the low Mw system. Incorporating the aligned films into photodetectors results in a polarized photocurrent ratio of 15.25 with corresponding anisotropy ratio of 0.88 at a wavelength of 530 nm, representing the highest reported photocurrent ratio for photodiodes that can operate in a self‐powered regime. The demonstrated performance showcases the ability of polymer semiconductors to achieve BHJ films with exceptional in‐plane polymer alignment, enabling high performance polarization sensitive photodetectors for incorporation into novel device architectures.

Intrinsic Linear Dichroism of Organic Single Crystals toward High-Performance Polarization-Sensitive Photodetectors.

The ability to detect light in photodetectors is central to practical optoelectronic applications, which has been demonstrated in inorganic semiconductor devices. However, so far, the study of polarization-sensitive organic photodetectors, which have unique applications in flexible and wearable electronics, has not received much attention. Herein, the construction of polarization-sensitive photodetectors based on the single crystals of a superior optoelectronic organic semiconductor, 2,6-diphenyl anthracene (DPA), is demonstrated. The systematic characterization of two-dimensionally grown DPA crystals with various techniques definitely show their strong anisotropy in molecular vibration, optical reflectance and optical absorption. In terms of polarization sensitivity, DPA-crystal based photodetectors exhibit a linear dichroic ratio up to ≈1.9. Theoretical calculations confirm that intrinsic linear dichroism, originated from the anisotropic in-plane crystal structure, is responsible for the polarization sensitivity of DPA crystals. This work opens up a new door for exploiting organic semiconductors for developing highly compact polarization photodetectors and providing new functionalities in novel flexible optical and optoelectronic applications.

Strongly polarized light from highly aligned electrospun luminescent natural rubber fibers

We report the production of luminescent natural rubber micro/nanofibers with high polarized photoemission. The electrospinning technique was used to produce aligned mats from natural rubber. The fibers have diameters that vary between 200 nm and 2.5 μm and with a mean diameter size around 820 nm. The produced fibers were parallel aligned, presenting optical transparency and pronounced birefringence due to polymeric chain alignment. Luminescent elastomeric fibers were produced using a benzothiadiazole-based organic luminescent small molecule dispersed in the natural rubber precursor solution before electrospinning. The photoluminescence spectrum of the fibers indicates that the vibrational resolution is higher than for this luminescent molecule in solution and membrane. This observation was attributed to the molecular packing inside the anisotropic fiber structure, which reduces the degrees of freedom and the molecular interactions of the dye. Therefore, resulting in pronounced linear polarized emission, which could still be improved by stretching along the fiber longitudinal direction, where a dichroic ratio of 13.0 and anisotropy factor of 0.98 were obtained. The experimental observations were supported by theoretical modelling. Such a system offers great potential for technological applications like optical sensors to monitor changes in the emission degree of polarized light when exposed to different ambient conditions.

Design of experiment optimization of aligned polymer thermoelectrics doped by ion-exchange

Organic thermoelectrics offer the potential to deliver flexible, low-cost devices that can directly convert heat to electricity. Previous studies have reported high conductivity and thermoelectric power factor in the conjugated polymer poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT). Here, we investigate the thermoelectric properties of PBTTT films in which the polymer chains were aligned uniaxially by mechanical rubbing, and the films were doped by a recently developed ion exchange technique that provides a choice over the counterions incorporated into the film, allowing for more optimized morphology and better stability than conventional charge transfer doping. To optimize the polymer alignment process, we took advantage of two Design of Experiment (DOE) techniques: regular two-level factorial design and central composite design. Rubbing temperature Trub and post-alignment annealing temperature Tanneal were the two factors that were most strongly correlated with conductivity. We were able to achieve high polymer alignment with a dichroic ratio >15 and high electrical conductivities of up to 4345 S/cm for transport parallel to the polymer chains, demonstrating that the ion exchange method can achieve conductivities comparable/higher than conventional charge transfer doping. While the conductivity of aligned films increased by a factor of 4 compared to unaligned films, the Seebeck coefficient (S) remained nearly unchanged. The combination of DOE methodology, high-temperature rubbing, and ion exchange doping provides a systematic, controllable strategy to tune structure–thermoelectric property relationships in semiconducting polymers.

Ultrathin Polythiophene Films Prepared by Vertical Phase Separation for Highly Stretchable Organic Field‐Effect Transistors

AbstractPhysically blending semiconducting conjugated polymers with elastomeric materials and precisely controlling the resulting film structure provides an effective strategy to obtain intrinsically stretchable semiconducting polymers. Here, vertically phase‐separated ultrathin poly(3‐hexylthiophene) (P3HT) and polystyrene‐b‐polyisoprene‐b‐polystyrene (SIS) blend films are developed for one‐step fabrication of semiconductor and insulator layers of organic field effect transistors (OFETs). The phase‐separated structure, surface morphology, and tensile deformation are characterized by UV–vis absorption spectroscopy, atomic force microscopy, and optical microscopy. The blend film device maintains 43% of its mobility compared with 0.1% mobility of the pristine P3HT films after 50% stretch. The deformability of the films is efficiently improved by blending proved by both the finite element analysis and the dichroic ratio measurements. The P3HT/SIS blended films possess reproducible properties under 200 continuous stretch–release cycles at a strain of 50% without significantly reduced mobilities. The fully‐stretchable OFETs on polydimethylsiloxane substrate are also investigated and show a stretchability up to 70% and good electrical recovery properties after stretch–release process. The vertical phase‐separated structure obtained by the blends provides an effective way to easily fabricate stretchable devices with a balance between their mechanical and electrical properties.

Remarkable Increase of Fluorescence Quantum Efficiency by Cyano Substitution on an ESIPT Molecule 2-(2-Hydroxyphenyl)benzothiazole: A Highly Photoluminescent Liquid Crystal Dopant

Fluorescent molecules with excited-state intramolecular proton transfer (ESIPT) character allow the efficient solid-state luminescence with large Stokes shift that is important for various applications, such as organic electronics, photonics, and bio-imaging fields. However, the lower fluorescence quantum yields (ΦFL) in the solution or viscous media, due to their structural relaxations in the excited state to reach the S0/S1 conical intersection, shackle further applications of ESIPT-active luminophores. Here we report that the introduction of a cyano group (-CN) into the phenyl group of 2-(2-hydroxyphenyl)benzothiazole (HBT), a representative ESIPT compound, remarkably increase its fluorescence quantum yield (ΦFL) from 0.01 (without -CN) to 0.49 (with -CN) in CH2Cl2, without disturbing its high ΦFL (=0.52) in the solid state. The large increase of the solution-state ΦFL of the cyano-substituted HBT (CN-HBT) is remarkable, comparing with our previously reported ΦFL values of 0.05 (with 4-pentylphenyl), 0.07 (with 1-hexynyl), and 0.15 (with 4-pentylphenylethynyl). Of interest, the newly-synthesized compound, CN-HBT, is miscible in a conventional room-temperature nematic liquid crystal (LC), 4-pentyl-4′-cyano biphenyl (5CB), up to 1 wt% (~1 mol%), and exhibits a large ΦFL of 0.57 in the viscous LC medium. A similar ΦFL value of ΦFL = 0.53 was also recorded in another room-temperature LC, trans-4-(4-pentylcyclohexyl)benzonitrile (PCH5), with a doping ratio of 0.5 wt% (~0.5 mol%). These 5CB/CN-HBT and PCH5/CN-HBT mixtures serve as light-emitting room-temperature LCs, and show anisotropic fluorescence with the dichroic ratio of 3.1 upon polarized excitation, as well as electric field response of luminescence intensity changes.

Extreme Orientational Uniformity in Large-Area Floating Films of Semiconducting Polymers for Their Application in Flexible Electronics.

Layer-by-layer fabrication of uniformly oriented thin films over large areas by cost-effective solution-based approaches can open new horizons for the realization of high-performance organic circuits in various applications. In this work, fabrication of a large-area ≈40 cm2 film with uniform orientation is reported for poly(3,3‴-dialkylquaterthiophene) (PQT) using a unidirectional floating film transfer method (UFTM). Orientation characteristics and charge transport anisotropy were analyzed using polarized UV-vis spectral mapping and fabrication of bottom-gated organic field-effect transistors (OFETs) from different regions. Films were found to be highly oriented with an optical dichroic ratio of ca. 15. Orientation characteristics reveal that films were highly oriented along the width of the film, covering >70% of the area, and angle-dependent field-effect mobilities are in good agreement with the orientation of the polymer backbones. These highly oriented films resulted in charge transport anisotropy of 8.9. An array of bottom-gated OFETs fabricated along the length of single large-area (≈15 × 2.5 cm2) thin film demonstrated the average field-effect mobility of 0.0262 cm2/(V s) with a very narrow standard deviation of 12.6%. We also demonstrated that film thickness can be easily tuned from 5.6 to 45 nm by increasing the PQT concentration, and field-effect mobility is highly reproducible even when the film thickness is 10 nm. Microstructural characterization of the thus-prepared large-area thin films revealed the edge-on stacked polymer backbones and surface roughness of <1 nm as probed by grazing incidence X-ray diffraction and atomic force microscopy, respectively. Flexible OFETs with bottom-gate top-contact geometry were also fabricated, having average field-effect mobility of 0.0181 cm2/(V s). There was no considerable change in mobility after bending the flexible devices at different radii.

Tunable Alloying Improved Wide Spectrum UV-Vis-NIR and Polarization-Sensitive Photodetector Based on Sb–S–Se Nanowires

Polarization-sensitive photodetector based on low-dimensional semiconductor is a kind of special photoelectric device which can take advantage of the semiconductor's anisotropy and convert it into an electrical signal. However, the polarization performance of the photodetector is limited by the challenges of the anisotropy of semiconductors. The design of alloy semiconductors with excellent anisotropy is one of the mainstream methods to improve the dichroic ratio of the polarization-sensitive photodetector. Here, we design the tunable alloying Sb-S-Se nanowires (NWs), which can be used in the research field of polarization-sensitive photodetectors because of their low symmetry crystal structure, suitable bandgap, and high mobility. It is demonstrated that the metal-semiconductor-metal polarization-sensitive photodetector based on Sb-S-Se NWs has great photoelectric properties and polarization performance in UV-Vis-near-infrared response (NIR) spectrum. Under the irradiation laser of the 532-nm, the photoresponsivity ( R) and detectivity ( D*) of the Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/3</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2/3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> NW-based polarization-sensitive photodetector can reach 6.38 A/W and 1.63 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> Jones. By investigating the polarization characteristics of the photodetector, the dichroic ratio of the photodetector can reach 3.8 at 532 nm. By regulating the proportion of each component in the alloy semiconductor, an effective method is provided for adjusting the photoresponse spectrum and optimizing the performance of the polarization-sensitive photodetector, which has a promising research prospect in the future.

Assisted alignment of conjugated polymers in floating film transfer method using polymer blend

Orientating conjugated polymers (CPs) in thin films is an attractive technique for obtaining anisotropic properties, resulting in improved device performances. Template-assisted alignment using pre-patterned substrates has been widely used to orient various polymers irrespective of their orientation capability. In this work, we report that using the floating film transfer method, the orientation of guest polymers can be in-situ assisted via blending with a host polymer during film fabrication. Dichroic Ratio (DR) of two guest CPs such as poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] and poly(9,9-di-n-octylfluorenyl-2,7-diyl) were found to be enhanced when blended with host polymer poly(3,3‴-didodecyl-quaterthiophene) (PQT). DR of the host PQT decreases monotonically with an increase in the guest polymer proportion, suggesting that guest polymers are well mixed in the host matrix. The electronic absorption spectra and atomic force microscopy results revealed that blended polymers were well mixed without any phase separation. DR of the guest polymers in the blend was the same even when the overall blend concentration was increased twice to increase the overall film thickness.

Luminescent Liquid Crystals Based on Carbonized Polymer Dots and Their Polarized Luminescence Application.

Traditional luminescent liquid crystals (LLCs) suffer from fluorescence quenching caused by aggregation, which greatly limits their further application. In this work, a kind of novel LLCs (named carbonized polymer dot liquid crystals (CPD-LCs)) are designed and successfully synthesized through grafting the rod-shaped liquid crystal (LC) molecules of 4'-cyano-4-(4″-bromohexyloxy) biphenyl on the surface of CPDs. The peripheral LC molecules not only increase the distance between different CPDs to prevent them from aggregating and reduce intermolecular energy resonance transfer but also make this LLC have an ordered arrangement. Thus, the obtained CPD-LCs show good LC property and excellent high luminous efficiency with an absolute photoluminescence quantum yield of 14.52% in the aggregated state. Furthermore, this kind of CPD-LC is used to fabricate linearly polarized devices. The resultant linearly polarized dichroic ratio (N) and polarization ratio (ρ) are 2.59 and 0.44, respectively. Clearly, this type of CPD-LC shows promising applications for optical devices.

Two-Dimensional Guanidine-Based Hybrid Perovskites with Strong Dichroism for Multiwavelength Polarization-Sensitive Detection.

Two-dimensional (2D) organic-inorganic hybrid perovskites, benefiting from their natural anisotropy of quantum-well motifs and optical properties, have shown remarkable polarization-dependent responses superior to the 3D counterparts. Here, for the first time, multiwavelength polarization-sensitive detectors were fabricated by using single crystals of a guanidine-based 2D hybrid perovskite, (BA)2 (GA)Pb2 I7 (where BA+ is n-butylammonium and GA+ is guanidium). Its unique 2D quantum-well structure results in strong crystallographic-dependence of optical absorption. Strikingly, our crystal-based photodetector exhibits a prominent photocurrent dichroic ratio (Imax /Imin ) of ∼2.2 at 520 nm, higher than the typical 2D inorganic materials (GeSe, ∼1.09, PdSe2 , ∼1.8). In addition, notable dichroic ratios of 1.29 and 1.23 at 405 nm and 637 nm are also created for the multiwavelength polarized-light detection. The prominent detecting performances, including low dark current (1.6×10-11 A), considerable on/off ratio (∼2×103 ), high photodetectivity (∼3.3×1011 Jones) and responsivity (∼12.01 mA W-1 ), make (BA)2 (GA)Pb2 I7 a promising candidate for polarized-light detection. This work sheds light on the rational engineering of new 2D hybrid perovskites for the high-performance optoelectronic device applications.

Low-Noise Dual-Band Polarimetric Image Sensor Based on 1D Bi2 S3 Nanowire.

With the increasing demand for detection accuracy and sensitivity, dual‐band polarimetric image sensor has attracted considerable attention due to better object recognition by processing signals from diverse wavebands. However, the widespread use of polarimetric sensors is still limited by high noise, narrow photoresponse range, and low linearly dichroic ratio. Recently, the low‐dimensional materials with intrinsic in‐plane anisotropy structure exhibit the great potential to realize direct polarized photodetection. Here, strong anisotropy of 1D layered bismuth sulfide (Bi2S3) is demonstrated experimentally and theoretically. The Bi2S3 photodetector exhibits excellent device performance, which enables high photoresponsivity (32 A W−1), I on/I off ratio (1.08 × 104), robust linearly dichroic ratio (1.9), and Hooge parameter (2.0 × 10−5 at 1 Hz) which refer to lower noise than most reported low‐dimensional materials‐based devices. Impressively, such Bi2S3 nanowire exhibits a good broadband photoresponse, ranging from ultraviolet (360 nm) to short‐wave infrared (1064 nm). Direct polarimetric imaging is implemented at the wavelengths of 532 and 808 nm. With these remarkable features, the 1D Bi2S3 nanowires show great potential for direct dual‐band polarimetric image sensors without using any external optical polarizer.

Cross-Substitution Promoted Ultrawide Bandgap up to 4.5eV in a 2D Semiconductor: Gallium Thiophosphate.

Exploring 2D ultrawide bandgap semiconductors (UWBSs) will be conductive to the development of next-generation nanodevices, such as deep-ultraviolet photodetectors, single-photon emitters, and high-power flexible electronic devices. However, a gap still remains between the theoretical prediction of novel 2D UWBSs and the experimental realization of the corresponding materials. The cross-substitution process is an effective way to construct novel semiconductors with the favorable parent characteristics (e.g., structure) and the better physicochemical properties (e.g., bandgap). Herein, a simple case is offered for rational design and syntheses of 2D UWBS GaPS4 by employing state-of-the-art GeS2 as a similar structural model. Benefiting from the cosubstitution of Ge with lighter Ga and P, the GaPS4 crystals exhibit sharply enlarged optical bandgaps (few-layer: 3.94eV and monolayer: 4.50eV) and superior detection performances with high responsivity (4.89 A W-1 ), high detectivity (1.98×1012 Jones), and high quantum efficiency (2.39×103 %) in the solar-blind ultraviolet region. Moreover, the GaPS4 -based photodetector exhibits polarization-sensitive photoresponse with a linear dichroic ratio of 1.85 at 254nm, benefitting from its in-plane structural anisotropy. These results provide a pathway for the discovery and fabrication of 2D UWBS anisotropic materials, which become promising candidates for future solar-blind ultraviolet and polarization-sensitive sensors.

Exciton-Phonon Interaction-Induced Large In-Plane Optical Anisotropy in Two-Dimensional All-Inorganic Perovskite Crystals.

Two-dimensional (2D) perovskites are an emerging class of layered materials with unique optoelectronic properties. To date, most 2D perovskites with Ruddlesden-Popper (RP) phase reported are organic- inorganic hybrid perovskites with long organic spacers. Here, we report a high-quality all-inorganic 2D perovskite, Cs2PbI2Cl2, synthesized by an aqueous method. The as-synthesized perovskite crystals exhibit large in-plane emission and reflection optical anisotropy. The maximum in-plane linear dichroic ratio is up to 9.6 for exciton emission and 2.0 for reflection at 77 K. The large in-plane optical anisotropy may be ascribed to the strong electron-phonon interaction-induced lattice distortion. The large optical anisotropy enables us to construct a polarization-sensitive photodetector based on this perovskite, for which the linear dichroic ratio of photoresponse is about 1.2. Our study provides an alternative avenue to achieve in-plane optical anisotropy in an isotropy structure and thus would be of great importance for polarization-associated applications.

Synergistic Additive-Assisted Growth of 2D Ternary In2 SnS4 with Giant Gate-Tunable Polarization-Sensitive Photoresponse.

2D ternary materials exhibit great promise in the field of polarization-sensitive photodetectors due to the low-symmetry crystal structure. However, the realization of ternary material growth is still a huge challenge because of the complex reaction process. Here, for the first time, 2D ternary In2 SnS4 flakes are obtained via synergistic additive of salt and molecular sieve-assisted chemical vapor deposition. Raman vibration mode of In2 SnS4 flakes exhibits polarization-dependent properties. The polarization-resolved absorption spectroscopy and azimuth-dependent reflectance difference microscopy further confirm its anisotropy of in-plane optical absorption and reflection. Besides, the In2 SnS4 flake based device on mica shows ultrafast rising and decay rates of ≈20 and 20 µs. Impressively, In2 SnS4 flake based phototransistor demonstrates giant gate-tunable polarization-sensitive photoresponse: the dichroic ratio can be adjusted in the range of 1.13-1.70 with gate voltage varying from -35-35V. This work provides an effective means for modulating the polarization-sensitive photoresponse, which may significantly promote the research progress of polarization-sensitive photodetectors.

Low‐Symmetry and Nontoxic 2D SiP with Strong Polarization‐Sensitivity and Fast Photodetection

AbstractThe in‐plane anisotropic feature of 2D layered materials has captured enormous research interest due to their application in polarization‐sensitive photodetection. Here, silicon phosphide (SiP), as a novel member of group IV–V 2D materials, is first introduced to the anisotropic 2D materials family with a high in‐plane anisotropy. The low‐symmetry structure, optical and optoelectronic properties are investigated systematically. Impressively, the photodetectors based on 2D SiP demonstrate high performance with low dark current, a fast response speed of 30 µs, and a strong anisotropic photoresponse with an anisotropic factor of 2.9. Furthermore, a strong polarization‐sensitive photodetector with a dichroic ratio up to 2.3 is realized based on the intrinsic linear dichroism of 2D SiP. This work not only provides an insight into the in‐plane anisotropic properties of 2D SiP, but also sheds light on its great potentials in anisotropic optoelectronic applications.

Short-Wave Near-Infrared Polarization Sensitive Photodetector Based on GaSb Nanowire

The near-infrared (NIR) polarized photodetector has wide range of applications including the object identification. Wavelength of 1550 nm is the least loss band for transmission communication, and the study of photodetectors working at 1550 nm demonstrate special scientific and applied significances. GaSb has attracted tremendous attention in the field of photoelectric detection due to its suitbale band gap, high mobility, sensitivity, and good compatibility with modern microelectronics technology. In this work, a highly polarization-sensitive GaSb nanowire-based photodetectors under short-wave near-infrared photoelectric detection is achieved. The device has a good optical detection ability in the near-infrared band, and showed the responsivity up to 77.3 A/W with the external quantum efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.18\times 10 ^{3}$ </tex-math></inline-formula> % (illumination intensity of 1.59 mW/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) under 1550 nm. Furthermore, obvious photocurrent anisotropy are investigated under the near-infrared band from 808 nm to 1550 nm. The largest dichroic ratio reaches 3.3 at 1550 nm. These results indicate that GaSb nanowire based photodetectors are not only promising candidates for NIR detection but also have promising potentials in polarization sensitive applications.

Highly In-Plane Polarization-Sensitive Photodetection in CsPbBr3 Single Crystal

The fully inorganic perovskite lead cesium bromide single crystal (CsPbBr3 SC) is considered as an excellent candidate semiconductor for photodetectors because of its superior humidity resistance, thermal stability, and light stability compared with organic-inorganic hybrid perovskites as well as its photoelectric properties such as large light absorption coefficient and ultralong carrier migration distance. In this Letter, we utilize the inverse temperature solubility of CsPbBr3 in ternary solvents to grow large-sized CsPbBr3 SCs. By the use of the (101) plane, CsPbBr3 SC-based photodetectors are fabricated, which exhibit excellent polarized light response characteristics. The photocurrent relies on the polarization angle in a sinusoidal fashion and shows strong anisotropic optoelectronic properties. The photodetection performance perpendicular to the y axis is significantly higher than that parallel to the y axis, and the dichroic ratio under 405 nm illumination at a bias voltage of 1 V reaches 2.65. The experimental results are consistent with the results of first-principles calculations.