Single Crystal Photodetectors Research Articles

γ‐Valerolactone Enabling Spontaneously Inhibited Iodide Oxidation for High‐Quality Perovskite Single Crystal Fabrication

AbstractThe iodide precursor oxidation has persistently plagued solution grown iodine‐based perovskite single crystals (IPSCs) that inevitably introduce undesirable triiodide ion (I3−) defects and severely hindering crystal quality, despite IPSCs having garnered remarkable progress in multifarious photoelectronic applications. In this work, the spontaneously inhibited iodide oxidation is discovered in an eco‐friendly solvent, γ‐Valerolactone (GVL), and demonstrates a universal solution approach for fabricating high‐quality IPSCs. Compared to the routine γ‐Butyrolactone (GBL) system, GVL provides a lowered growth temperature and a significantly broadened inverse temperature operation window, thereby improving the theoretical utilization rate of perovskite precursors up to 88.6%. More importantly, due to its higher open‐ring hydrolysis energy, GVL can spontaneously inhibit the iodide precursors oxidation without any additional reductant and therefore effectively prevent the forming I3− defects. Typically, the as‐fabricated MAPbI3 single crystal possesses an extremely low trap density of 3.57 × 108 cm−3 and a high carrier mobility‐lifetime (µτ) product of 2.74 × 10−3 cm2 V−1, which enables its photodetection capabilities to be on a par with the state‐of‐art MAPbI3 single crystal photodetectors. This work paves an efficacious and green pathway for high‐quality IPSC fabrication toward advanced optoelectronic utilizations.

Day-Night imaging without Infrared Cutfilter removal based on metal-gradient perovskite single crystal photodetector

Day-Night imaging technology that obtains full-color and infrared images has great market demands for security monitoring and autonomous driving. The current mainstream solution relies on wide-spectrum silicon photodetectors combined with Infrared Cutfilter Removal, which increases complexity and failure rate. Here, we address these challenges by employing a perovskite photodetector based on Pb−Sn alloyed single crystal with a vertical bandgap-graded structure that presents variable-spectrum responses at different biases and extends the infrared detection range close to 1100 nm. Taking advantage of the Pb−Sn gradients in mobility and built-in field, the perovskite photodetector shows a large linear dynamic range of 177 dB. In addition, the optoelectronic characteristics feature long-term operational stability over a year. We further develop an imaging module prototype without Infrared Cutfilter Removal that exhibits excellent color fidelity with RGB color differences ranging from 0.48 to 2.46 under infrared interference and provides over 26-bit grayscale resolution in infrared imaging.

Single Crystal Ruddlesden-Popper and Dion-Jacobson Metal Halide Perovskites for Visible Light Photodetectors: Present Status and Future Perspectives.

2D metal halide perovskites (MHPs), mainly the studied Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phases, have gained enormous popularity as optoelectronic materials owing to their self-assembled multiple quantum well structures, tunable semiconducting properties, and improved structural stability compared to their bulk 3D counterparts. The performance of polycrystalline thin film devices is limited due to the formation of defects and trap states. However, as studied so far, single crystal-based devices can provide a better platform to improve device performance and investigate their fundamental properties more reliably. This Review provides the first comprehensive report on the emerging field of RP and DJ perovskite single crystals and their use in visible light photodetectors of varied device configurations. This Review structurally summarizes the 2D MHP single crystal growth methods and the parameters that control the crystal growth process. In addition, the characterization techniques used to investigate their crystal properties are discussed. The review further provides detailed insights into the working mechanisms as well as the operational performance of 2D MHP single crystal photodetector devices. In the end, to outline the present status and future directions, this Review provides a forward-looking perspective concerning the technical challenges and bottlenecks associated with the developing field of RP and DJ perovskite single crystals. Therefore, this timely review will provide a detailed overview of the fast-growing field of 2D MHP single crystal-based photodetectors as well as ignite new concepts for a wide range of applications including solar cells, photocatalysts, solar H2 production, neuromorphic bioelectronics, memory devices, etc.

Lattice Manipulation with Di-Tertiary Ammonium Spacer in Bismuth Bromide Perovskite Directs Efficient Charge Transport and Suppressed Ion Migration for Photodetector Applications.

Bismuth halide hybrid perovskites have emerged as promising alternatives to their lead halide homologs because of high chemical stability, low toxicity, and structural diversity. However, their advancements in optoelectronic field are plagued with poor charge transport, due to considerable microstrain triggered by bulky spacer. Herein, the di-tertiary ammonium spacer (N,N,N',N'-tetramethyl-1,4-butanediammonium, TMBD) is explored to direct stable 1D bismuth bromide lattice structure with relaxed microstrain. Compared to the primary pentamethylenediamine (PD)2+, the (TMBD)2+ adopting alternating alignment enables a unique H-bonds mode to distort the configuration of inorganic layers to form corner-sharing [BiBr5] near-regular chains with narrower bandgap, lower exciton binding energy, and reduced carrier-lattice interactions, thereby facilitating charge-carrier transport. Moreover, the (TMBD)2+ spacers largely suppress ion migration in perovskite lattice, as substantiated by the experimental and theoretical investigations. Consequently, (TMBD)BiBr5 single crystal photodetector delivers a 185-fold increase in current on/off ratio with respect to (PD)BiBr5 under white light irradiation, considerable responsivity (≈82.97mA W-1), detectivity (≈8.06 ×1011 Jones) under weak light (0.02mW cm-2) irradiation, in the top rank of the reported hybrid bismuth halide perovskites. This finding offers novel design criterion for high-performance lead-free perovskites.

Mitigating Noise Current in 2D Perovskite Single Crystal Photodetectors for Imaging under Black‐Light Condition

AbstractWeak‐light imaging plays a pivotal role in various fields such as astronomical photography, military nighttime surveillance, and biomedical imaging. The capability of photodetectors (PDs) in detecting weak‐light relies heavily on minimizing their noise current. In this study, the weak‐light detection performances of PDs constructed from PEA2MAn‐1PbnI3n+1 (n = 1, 2, 3) 2D perovskite single crystals are presented. Among these, the n = 1 PD showcases incredibly low noise current that induces an ultra‐low detection limit of 14 pW cm−2 under 532 nm light illumination, and a high detectivity of 3.25 × 1015 Jones. The n = 1 PD also meets imaging requirements even under black‐level illumination conditions of 75 pW cm−2. The investigation reveals that decreasing n value corresponds to an increase in the PEA+ ratios of cations, resulting in reduced defects and enhanced ion migration activation energy and exciton binding energy. These reduce noise current of devices from electron/hole, ion, and exciton dynamic behaviors. Notably, inhibiting ion migration can significantly improve the stability of the noise current baseline and facilitate the stable detection of weak signals. This study underscores the potential of 2D perovskites for advancing weak‐light imaging technologies, offering valuable insights for future development in this field.

Highly-Polarized Solar-Blind Ultraviolet Organic Photodetectors.

Developing high-performance polarization-sensitive ultraviolet photodetectors is crucial for their application in military remote sensing, detection, bio-inspired navigation, and machine vision. However, the significant absorption in the visible light range severely limits the application of polarization-sensitive ultraviolet photodetectors, such as high-quality anti-interference imaging. Here, based on a wide-bandgap organic semiconductor single crystal (trans-1,2-bis(5-phenyldithieno[2,3-b:3',2'-d]thiophen-2-yl)ethene, BPTTE), high-performance polarization-sensitive solar-blind ultraviolet photodetectors with a dichroic ratio close to 4.26 are demonstrated. The strong anisotropy of 2D grown BPTTE single crystals in molecular vibration and optical absorption is characterized by various techniques. Under voltage modulation, stable and efficient detection of polarized light is demonstrated, attributed to the intrinsic anisotropy of transition dipole moment in the bc crystal plane, rather than other factors. Finally, high-contrast polarimetric imaging and anti-interference imaging are successfully demonstrated based on BPTTE single crystal photodetectors, highlighting the potential of organic semiconductors for polarization-sensitive solar-blind ultraviolet photodetectors.

CVT grown CuSe single crystals: Unveiling photodetection advancements and thermoelectric promise

Over the past few decades, transition metal chalcogenides garnered global recognition for their noteworthy contributions to the modeling and engineering of electronic, optoelectronic, and thermoelectric devices to improve overall device performance. In the current investigation, the first ever growth of CuSe single crystals is achieved utilizing the chemical vapor transport technique with iodine serving as a transporting medium. The ascertainment of the hexagonal unit cell configuration in the grown CuSe crystals with the P63/mmc space group is substantiated via powder X-ray diffraction examination. The micro-surface characteristics exhibited planar facets outlined by layer boundaries, signifying crystal development through a mechanism reliant on layer growth. The direct optical bandgap of 1⋅64 eV for CuSe single crystals is unveiled by optical reflectance spectrum, demonstrating its aptitude for incorporation into photodetectors. The Raman spectrum manifested a prominent peak at 259 cm−1, aligning to Ag1 vibrational mode. The exploration of temperature-induced fluctuations in the power factor and figure of merit unveiled a progressive increase with rising temperatures. The optimal ZT parameter for the CuSe single crystals attains 0⋅058 at 523 K. The thermogravimetric patterns of CuSe single crystals exhibited singular step decomposition, exemplified by an average weight reduction of 25⋅49 % across the temperature spectrum from ambient to 813 K. The current−voltage (I–V) features of the fabricated CuSe single crystal photodetector are assessed under biasing voltage set at 20 mV at ambient temperature. Under a bias voltage of 20 mV and a polychromatic light intensity of 50 mW/cm2, the achieved responsivity is 4335⋅57 μA/W and a detectivity of 135 × 106 Jones. The photoresponse and thermoelectric examination of CuSe crystals alludes to their potential utility in innovative applications on the horizon.

Fabrication of ZnSnO3 single crystal films on sapphire substrates by pulsed laser deposition for solar-blind photodetectors

ZnSnO3 single crystal films were prepared on c-plane sapphire substrates using pulsed laser deposition and post-annealing methods. For the as-grown sample at 700 °C, post-annealing at 700 °C resulted in a significant improvement in the crystalline quality of the single crystal films, while post-annealing at 800 °C led to decomposition of ZnSnO3. Compared with the amorphous and mixed crystal ZnSnO3-based photodetectors (PDs), the single crystal ZnSnO3-based PD has a better light-to-dark current ratio (1.32 × 106) and higher responsivity (8.71 A/W) at 5 V under 254-nm UV (1.1 mW/cm2) illumination. Such a good performance serves as resounding validation of the remarkable potential of ZnSnO3 epitaxial films in the context of solar-blind PDs.

Dimensionality Engineering of Lead Organic Chalcogenide Semiconductors.

Two-dimensional (2D) metal organic chalcogenides (MOCs) such as silver phenylselenolate (AgSePh) have emerged as a new class of 2D materials due to their unique optical properties. However, these materials typically exhibit large band gaps, and their elemental and structural versatility remain significantly limited. In this work, we synthesize a new family of 2D lead organic chalcogenide (LOC) materials with excellent structural and dimensionality tunability by designing the bonding ability of the organic molecules and the stereochemical activity of the Pb lone pair. The introduction of electron-donating substituents on the benzenethiol ligands results in a series of LOCs that transition from 1D to 2D, featuring reduced band gaps (down to 1.7 eV), broadband emission, and strong electron-phonon coupling. We demonstrated a prototypical single crystal photodetector with 2D LOC that showed the dimensionality engineering on the transport property of LOC semiconductors. This study paves the way for further development of the synthesis and optical properties of novel organic-inorganic hybrid 2D materials.

Bridgman grown CuSbS2 single crystal and its application as photodetector and potential thermoelectric material

Crystal of copper antimony disulphide (CuSbS2) measuring 4.5 cm in length and 0.8 cm in diameter was successfully grown using the vertical Bridgman technique (VBT). The orthorhombic unit cell structure and pure CuSbS2 phase of the grown crystal was confirmed by the powder X-ray diffraction and was well supported by Raman spectra. The stoichiometry of the grown crystal was confirmed by energy dispersive X-ray analysis and field emission scanning electron microscopy revealed that crystal is grown by layer growth mechanism. The Raman spectra has shown the presence of peak at 319.32 cm−1 corresponding to Sb-S bonds whereas peaks at 445.03 cm−1 and 257.27 cm−1 corresponds to S-S and Cu-S bonds. The photoluminescence spectra taken at room temperature with 488 nm excitation wavelength displays emission in different regions of the visible spectrum. Optical absorbance spectra shows that CuSbS2 single crystal possess direct bandgap of 1.57 eV which is suitable for solar cell application. The Seebeck coefficient is positive over the entire temperature range, demonstrating the sample's p-type semiconducting nature and corroborates our Hall effect measurements. Using electrical conductivity and lattice thermal conductivity values we calculated thermoelectric figure of merit i.e., ZT whose value comes nearly 0.988 at 503 K which stands in competition with reported values of the other grown crystal. Thermogravimetric (TG) curve has shown two step decomposition at four different heating rates of 5, 10, 15 and 20 K/min which is also confirmed from DTG (differential thermogravimetric analysis) curves. At room temperature, the I-V characteristics of prepared CuSbS2 single crystal photodetector are measured for parallel to plane and perpendicular to plane configuration, with various biasing voltages at 50 mW/cm2. At room temperature, a bias voltage of 0.1 V with a light intensity of 50 mW/cm2 yields responsivity and detectivity of 30 mA/W and 32.84 × 106 Jones for ⊥ to plane, which is comparable to the reported values of other materials.

Growth and High-Performance Photodetectors of CsPbBr3 Single Crystals.

Organic-inorganic hybrid perovskites have demonstrated exceptional photovoltaic properties, making them highly promising for solar cells and photodetectors (PDs). However, the organic components of these materials are vulnerable to heat and strong light illumination, limiting their application prospects. All-inorganic cesium-based perovskite PDs, on the other hand, possess enhanced thermal tolerance and stability, making them ideal for perovskite applications. The utilization of a ternary mixture solvent and additives in combination with single crystal (SC) growth has enabled the production of highly crystalline SCs with a defect density of 3.79 × 109 cm-3. The performance of the SC PDs had been evaluated using metal-semiconductor-metal devices, which demonstrated excellent results with a dark current as low as 0.198 μA at 10 V bias, on-off ratios exceeding 103, and a response time of shorter than 1 ms.

Enhancement of CsPbBr3 Perovskite Single-Crystal Photodetector Performance via Zr Ion Implantation

All-inorganic halide perovskite single crystals have attracted significant attention in optoelectronic fields on account of their outstanding optoelectronic properties. Photodetectors (PDs) based on CsPbBr3 single crystal exhibit high responsivity (R) and external quantum efficiency (EQE) due to the direct optical band gap, large optical absorption throughout the visible spectrum range, and long-term stability. Herein, we prepared the centimeter-size CsPbBr3 perovskite single crystal and utilized Zr ion implantation to modify the photoelectric properties of single crystals. The optical band gap of the CsPbBr3 single crystal decreases from 2.24 to 2.12 eV, and the absorption intensity increases after Zr ion implantation. The R and EQE of the CsPbBr3 single crystal photodetector modified by Zr ion implantation are 1.0 A W–1 and 294%, respectively, with a light intensity of 3.8 mW cm–2 and a 5 V bias under 425 nm illumination, which are ten times larger than that of the pristine devices. Meanwhile, the first-principles calculation results show that the introduction of Zr ions decreases the band gap and that the Zr 4d orbit contributes to the conduction band minimum (CBM), which facilitates carrier transport in Zr ion implanted CsPbBr3 single crystals. The results show that Zr ion implantation is an effective strategy to improve the performance of the CsPbBr3 single-crystal-based PDs.

Germanane and (3‐Hydroxypropyl)germanane as Single Crystal Photodetectors

Abstract2D materials are being widely investigated for their potential application in light‐detecting devices. Very recently, a spin‐coated flexible 2D germanium‐based photodetector with great photocurrent density and responsivity as well as short rise and decay time is presented by Liu et. al. In this paper, the solid‐state single flake photodetector base on either pure germanane or (3‐hydroxypropyl)germanane is reported. Both prepared photodetectors while irradiated with different wavelengths of light exhibit outstanding responsivity of 1157 mA W−1 for GeH and 362 mA W−1 for (3‐hydroxypropyl)germanane, which exceeds Liu's flexible reported GeH photodetector (22 µA W−1) by more than five orders of magnitude. These constructed photodetectors also exhibit rise and fall times lower than 20 ms, which is also significantly faster than the GeH photodetector reported by Liu with rise and decay times 240 and 740 ms, respectively.

Lead-Free Double Perovskite Semiconductor with Rigid Spacer-Induced High-Tc Dielectric Switch Features.

Layered hybrid perovskites possess exceptional semiconductor features and structural versality, making them viable candidates for developing multifunctional dielectric phase-transition materials (PTMS). However, most PTMs based on layered hybrid perovskites still suffer from Pb toxicity and low operating temperature. The recently developed hybrid double perovskites provide a new routine to designed PTMs with desired working performance and environment-friendly chemical compositions. Herein, using rigid aromatic cations as templates, we have successfully synthesized a novel double perovskite (benzylammonium)4 AgBiBr8 (1), which consists of corner-sharing AgBr6 and BiBr6 layers and benzylammonium cations. Notably, 1 exhibits a high-temperature first-order reversible solid-state phase transition at 383/387 K (cooling/heating) and switchable dielectric performance around the temperature. Compared with the soft organic chain version of the compound, the phase transition temperature of 1 shows a large enhancement of 99 K, validating the correctness of the designing strategy. In addition, 1 also exhibits semiconductor characteristics with a calculated bandgap of 2.34 eV and an optical bandgap of 2.29 eV. Remarkably, the single crystal photodetector of 1 shows a low dark current (2.12×10-13 A), a high on/off ratio (1.77×103 ), and a fast response (τrise =125 μs and τdecay =419 μs). Such a lead-free phase transition material combined with semiconductor properties provides a new strategy to develop environmentally friendly multifunctional materials.

On the photoresponse regulations by deep-level traps in CsPbBr3 single crystal photodetectors

The all-inorganic halide perovskite CsPbBr3 has attracted significant attention owing to its excellent opto-electronic properties. However, deep-level traps within the material are significant for the properties of CsPbBr3 based opto-electronic devices. In this study, the effects of deep-level traps on the photoresponse characteristics of CsPbBr3 photodetectors were thoroughly studied. By tailoring the illumination combinations where 532 nm light emitting diode (LED) illumination corresponds to the band-to-band excitation of photo-carriers and 648 nm LED illumination corresponds to sub-band excitation by the deep-level traps, it is proven that the device photoresponse performance is improved by the existence of deep-level traps. The photoresponsivity was enhanced by ∼63.64% (from 0.44 to 0.72 A W−1) under 3.18 μW cm−2 532 nm LED illumination. The rise/fall time was reduced by 21.95% (from 20.5 to 16.0 ms)/25.47% (from 21.2 to 15.8 ms). The underlying physical mechanisms of deep level trap-induced modulations on the photoresponse performance of the CsPbBr3 photodetector were revealed and discussed. By further systematic simulation of the effects of material properties on the photoresponse regulation, it was concluded that a shorter carrier lifetime, higher carrier mobility, higher trap concentration, and deeper trap level could improve the photoresponse of the CsPbBr3 photodetector. This study aims to clarify the physical relation between material properties and device performance and provide guidance for high-performance CsPbBr3 photodetector design.

Weak X-Ray to Visible Lights Detection Enabled by a 2D Multilayered Lead Iodide Perovskite with Iodine-Substituted Spacer.

Broadband photodetectors (PDs) with low detection limits hold significant importance to next-generation optoelectronic devices. However, simultaneously detecting broadband (i.e., X-ray to visible regimes) and weak lights in a single semiconducting material remains highly challenging. Here, by alloying iodine-substituted short-chain cations into the 3D FAPbI3 (FA = formamidine), a new 2D bilayered lead iodide hybrid perovskite, (2IPA)2 FAPb2 I7 (1, 2IPA = 2-iodopropylammonium), that enables addressing this challenge is reported. Such a 2D multilayered structure and lead iodide composition jointly endow 1 with a minimized dark current (6.04 pA), excellent electrical property, and narrow bandgap (2.03eV), which further gives it great potential for detecting broadband weak lights. Consequently, its high-quality single crystal PDs exhibit remarkable photoresponses to weak ultraviolet-visible lights (377-637nm) at several tens of nW cm-2 with high responsivities (>102 mA W-1 ) and significant detectivities (>1012 Jones). Moreover, 1 has an excellent X-ray detection performance with a high sensitivity of 438 µC Gy-1 cm-2 and an ultralow detection limit of 20 nGy s-1 . These exceptional attributes make 1 a promising material for broadband weak lights detection, which also sheds light on future explorations of high-performance PDs based on 2D hybrid perovskites.

Metal-organic framework single crystal infrared photodetector

Metal–organic frameworks (MOFs) are an emerging class of functional materials possessing the coupled optical and electrical responses necessary for the operation of modern optoelectronic devices. Yet, the realization of near infrared MOF-based photodetector is still a challenge. Here, we report on the MOF single crystal photodetector with 600–1000 nm spectral range, overlapping with the efficient optical absorption of the MOF (HKUST-1), converting the light energy to electric one. We detect that 0.1 s response rate of the detector turned out to be higher than the previously announced MOF-based photodetectors, that is due to the fairly fast and reversible process of desorption of coordinated water molecules underlying the mechanism of charge carrier generation. We also confirm the 1 mJ cm−2 fluence for the threshold photodetection due to a photostimulated change in the optical properties of the MOF, rather than its degradation, which paves the way to fast and multiple detection of a low-intensity infrared laser light on the MOF single crystal.

Improved optoelectronic performance from the internal secondary excitation of MAPbCl3-MAPbBr3 single crystal photodetectors

Single crystal (SC) MAPbBr 3 and MAPbCl 3 perovskite are considered promising materials for fabricating high-performance photodetectors (PDs) due to their impressive optoelectronic properties and good chemical stability. Structural modification of PDs is the fundamental solution to improve performance. In this paper, we designed a simple structure diagram considering photoelectric properties and the possibility of epitaxial crystal growth. Then a solution height restriction method (SHR) was used to grow the crystal and make the internal secondary excitation feasible. X-ray rocking curves (XRC) of MAPbBr 3 -SHR SCs show the quality of crystal under this growth method is excellent. X-ray photoelectron spectroscopy (XPS) measurements and Energy-dispersive X-ray spectroscopy (EDS) indicate element diffusion exists in the interface. Photoluminescence spectra (PL) and the photoelectric performance test have proved the existence and validity of the internal secondary excitation of crystals. Based on the above analysis, it was demonstrated that the inner MAPbCl 3 single-crystal enhances the optoelectronic performance of MAPbCl 3 -MAPbBr 3 crystals by the internal secondary excitation effect.

Ultrafast Response of Centimeter Scale Thin CsPbBr3 Single Crystal Film Photodetector for Optical Communication.

The photodetector (PD) is the key component to realize efficient optoelectronic conversion signal in the visible light communication (VLC) system. The response speed directly determines the bandwidth of the whole system. Metal halide perovskite is a neotype of low-cost solution processing semiconductor, with strong optical absorption, low trap density, and high carrier mobility, thus has been widely explored in photoelectric detection applications. However, previously reported perovskite polycrystalline photodetectors exhibit limited response speed due to the existence of grain boundaries. Here, an improved confined space method is developed through adjusting the heating area to control nucleation, resulting in centimeter scale fully inorganic perovskite CsPbBr3 thin single crystal films (SCFs) (<40µm). The smooth surface and high crystallinity of CsPbBr3 SCFs render admirable exciton lifetime. The planar metal-semiconductor-metal photodetector using CsPbBr3 SCF as the photosensitive layer demonstrates a limit response time of 200/300ns and a VLC within 100-500kHz frequency for both 365nm and white light, which is superior to previously reported CsPbBr3 polycrystalline filmand single crystal photodetectors.

Unraveling the Effect of Halogen Ion Substitution on the Noise of Perovskite Single-Crystal Photodetectors.

Halide mixing in perovskites has been an efficient way to engineer the bandgap, stability, and charge carrier mobility of lead halide perovskites, while its effect on the noise of lead halide perovskite photodetectors is still unknown. We present the preparation of mixed halide methylammonium lead perovskite single crystals by the solution temperature-decreasing method. Planar-structured photodetectors were constructed on the basis of these mixed halide perovskite single crystals. The effect of halogen ion substitution on the noise of devices was investigated by analyzing their dark current spectra. It is shown that the single-crystal photodetectors with higher levels of chloride suffer from larger noise thus have lower detectivity. Density functional theory calculations have also been proposed to reveal the effect of halogens on band structure. These results provide a comprehensive understanding of mixed halide perovskites and may help in the design and preparation of higher-performance devices.