Carrier Collection Efficiency Research Articles

Enhanced broadband quantum efficiency in LWIR T2SL detectors with guided-mode resonance structure.

Type-II superlattice (T2SL) detectors are emerging as key technologies for next-generation long-wavelength infrared (LWIR) applications, particularly in the 8-14 µm range, offering advantages in space exploration, medical imaging, and defense. A major challenge in improving quantum efficiency (QE) lies in achieving sufficient light absorption without increasing the active layer (AL) thickness, which can elevate dark current and complicate manufacturing. Traditional methods, such as thickening the absorber, are limited by the short carrier lifetime in T2SLs, necessitating alternative solutions. In this study, we introduced a guided-mode resonance (GMR) structure into T2SL LWIR detectors to enhance QE while maintaining a thin AL for efficient carrier collection. The GMR structure was fabricated by introducing a grating array on the surface of the detector and an Au mirror beneath the absorber. This configuration enhanced light trapping, which introduced additional resonance modes. The optimized grating design, with a 5 µm period and a fill factor of 0.6, significantly increased absorption, as predicted by finite-difference time-domain (FDTD) simulations and confirmed experimentally. The GMR-enhanced T2SL detector demonstrated a 2.58-fold improvement in QE over conventional LWIR detectors and a 1.33-fold increase compared to Fabry-Pérot (FP) resonance-based detectors in the 6-11 µm range. Despite exhibiting an almost identical dark current density, the GMR LWIR detector demonstrated superior performance, featuring a broader cut-off wavelength of 9.3 µm and higher QE compared to FP LWIR detectors.

High current density heterojunction bipolar transistors with 3D-GaN/2D-WSe2 as emitter junctions.

With the continuous advancement of electronic technology, there is an increasing demand for high-speed, high-frequency, and high-power devices. Due to the inherently small thickness and absence of dangling bonds of two-dimensional (2D) materials, heterojunction bipolar transistors (HBTs) based on 2D layered materials (2DLMs) have attracted significant attention. However, the low current density and limited structural design flexibility of 2DLM-based HBT devices currently hinder their applications. In this work, we present a novel vertical GaN/WSe2/MoS2 HBT with three-dimensional (3D)-GaN/2D-WSe2 as the emitter junction. Harnessing the high carrier concentration and wide bandgap of 3D-GaN, an HBT with a current density of about 260 A cm-2 is obtained. In addition, by selecting an adequate position for the collector electrode, we achieve efficient carrier collection through a collector junction smaller than the emitter junction area, obtaining a common-base current gain of 0.996 and a remarkable common-emitter current gain (β) of 12.4.

Constructing Chiral Core–Shell–Satellite Superstructures for Highly Efficient Antenna–Reactor Hot Electron Generation

AbstractIn hot electron (HE)‐driven photocatalysis, plasmonic metal nanocrystals with small size, or even nanoclusters, are preferrable. Antenna–reactor mechanism has been utilized to further boost the photocatalytic performance of the small reactor nanoparticles. The construction of a metal–semiconductor–metal core–shell–satellite (CSS) superstructure is demonstrated for highly efficient HE generation of the entire CSS architecture, where a mesoporous TiO2 (mTiO2) shell spatially separates the Au nanohelicoid (AuNH) antenna core and Au nanocluster (AuNC) reactor satellites. Individual AuNH@mTiO2@AuNC CSS superstructures are optically characterized using dark field scattering and circular differential scattering spectroscopies. The HE and circular differential HE photocurrent responses of the CSS superstructures are measured using a photoelectrochemical cell, where 12.4‐ and 8.3‐fold enhancements are respectively achieved with respect to that of the AuNHs. Electromagnetic simulations reveal that the contribution from the satellites with a small accumulative volume is almost equal to that from the core. Therefore, the specific‐volume HE rate of the satellites exhibit a high amplification ratio, 350, with respect to that of the core, being attributed to the antenna–reactor mechanism in the CSS architecture. Key factors are optimized, which includes small size of the plasmonic satellites, E‐field enhancement, and mesoporous semiconductor shell for efficient separation and collection of hot carriers.

Improving the performance of quantum well solar cells with photonic crystal.

The fabrication of quantum well solar cells with surface photonic crystal (SPC) and embedded photonic crystal (EPC) structures has resulted in solar cells with improved properties. When compared to reference solar cells (RSCs), the photoluminescence (PL) intensities of SPC solar cells and EPC solar cells have been enhanced by 89% and 114%, respectively. This indicates improved light absorption and emission characteristics in the presence of the periodic patterns (PCs). The short-circuit current (Isc) of EPC solar cells is 31% higher than that of RSCs, suggesting improved light absorption and carrier generation. On the other hand, SPC solar cells exhibit a 6% higher Isc compared to RSCs, and the open-circuit voltage has increased simultaneously. The fill factors (FF) of the solar cells are 84% for RSCs, 86% for SPC solar cells, and 76% for EPC solar cells. The higher FF in SPC solar cells suggests improved charge carrier collection efficiency. In terms of photoelectric conversion efficiency, SPC solar cells demonstrate a 10.6% increase, while EPC solar cells show a 7.7% increase. These improvements indicate that the incorporation of PCs in the solar cells enhances their ability to convert light into electrical energy. These findings highlight the potential of photonic crystals engineering for enhancing the performance of solar cells.

Visualization of Anion Vacancy Defect Annihilation in CZTSe Solar Cells by Hydrogen-Assisted Selenization with In Operando X-ray Nanoprobe Studies.

The traditional sulfur selenization process in Cu2ZnSn(S,Se)4 (CZTSSe) solar cell fabrication often results in the creation of localized anion vacancies (VS and VSe). These vacancies are considered harmful defects as they can trap carriers generated by light, leading to reduced solar cell efficiency. Moreover, concrete evidence has been lacking on the extent of the impact caused by these anion vacancies. Our research introduces a novel approach: the hydrogen-assisted selenization (HAS) process, specifically designed to minimize localized anion vacancies in Cu2ZnSnSe4 (CZTSe) solar cells. Our investigation, utilizing current-voltage (I-V) and admittance spectroscopy measurements, provides clear insights. We observed notable improvements in carrier collection efficiency and a discernible reduction in defect states. Furthermore, there was a significant decrease in the activation energy required within the solar cell device, dropping from 184 to 145 meV. To delve deeper into the structural and compositional aspects, we employed synchrotron-based X-ray nanoprobes. Through nanoscale X-ray fluorescence and hard X-ray beam-induced current measurements, we can directly observe and document the relationship between the local compositional distribution and photocurrent activity in operando. These comprehensive results furnish strong evidence that mitigating anion vacancies in the CZTSe layer can substantially improve the power conversion efficiency of the CZTSe solar cells. This advancement not only sheds light on the critical role of anion vacancies in solar cell performance but also underscores the effectiveness of the HAS process in enhancing overall device efficiency.

Theoretical study of the solution of the diffusion equation under effect of the magnetic field on the silicon solar cell

PurposeThe purpose of this study is to investigate the behavior of a silicon solar cell when subjected to a magnetic field. Specifically, the study aims to understand how the presence of the magnetic field influences the distribution of excess minority carriers within the base region of the solar cell. By solving the one-dimensional continuity equation under these conditions, the study seeks to elucidate the transient dynamics of carrier generation, recombination and transport processes. This research contributes to the broader understanding of how external magnetic fields can impact the performance and efficiency of silicon solar cells, potentially informing future optimizations or applications in photovoltaic technology.Design/methodology/approachThe solar cell is assumed to be uniformly illuminated, which simplifies the analysis of carrier generation to a function of depth (x). The emitter and space charge region contributions are considered while neglecting the diffusion region. The injection level remains constant throughout the analysis, focusing specifically on the base thickness region, H = 200 µm.FindingsThe findings of this study reveal significant insights into the behavior of a silicon solar cell under the influence of a magnetic field. Key findings include Impact on carrier distribution: the magnetic field affects the distribution of excess minority carriers within the base region of the solar cell. This distribution is crucial for understanding the efficiency of carrier collection and overall cell performance. Transient dynamics: the transient behavior of carrier generation, recombination and transport processes in the base region is influenced by the magnetic field. This understanding helps in predicting the response time and effectiveness of the solar cell under varying magnetic field strengths. Optimization potential: insights gained from this study suggest potential strategies for optimizing the design and operation of silicon solar cells to enhance their performance in environments where magnetic fields are present. Theoretical framework: the study provides a theoretical framework based on the one-dimensional continuity equation, offering a systematic approach to analyzing and predicting the behavior of solar cells under magnetic field conditions. These findings contribute to advancing the understanding of how external factors such as magnetic fields can impact the operation and efficiency of silicon solar cells, thereby guiding future research and development efforts in photovoltaic technology.Originality/valueThe originality and value of this study lie in its contribution to advancing the understanding of how magnetic fields influence silicon solar cell performance, providing both theoretical insights and potential practical applications in diverse technological contexts.

Reversing band bending at grain boundaries enables high-efficiency Cu2ZnSn(S,Se)4 solar cells

Kesterite solar cells show great potential for sustainable photovoltaic technology, attributed to their excellent semiconductor properties and earth abundant composition. However, undesirable band bending at the grain boundaries (GBs) in Cu2ZnSn(S,Se)4 (CZTSSe) films induces serious carrier recombination because of inhomogeneous distribution of S and Se in the grain interiors (GIs) and at GBs, which results in large open-circuit voltage deficit and overall poor performance of CZTSSe solar cells. Here, a robust hydrothermal sulfurization design has successfully inverted the band bending at the GBs, with advanced cathodoluminescence measurement confirming the transition of carrier collection pathways from the GBs to the GIs, thereby achieving efficient carrier collection within the GIs. Simultaneously, this design has effectively passivated the non-radiative recombination in the GIs, smoothing the way for carrier collection. Ultimately, a 13.7 % efficiency CZTSSe solar cell with 44 % improvement is realized by this process. This study discloses that reversing the band bending at GBs is practical to tailor the carrier collection, and thus pave the pathway for high-efficient photoelectronic devices.

Highly Efficient Organic/Silicon Hybrid Solar Cells with a MoO3 Capping Layer.

Organic/Si hybrid solar cells have attracted considerable attention for their uncomplicated fabrication process and superior device efficiency, making them a promising candidate for sustainable energy applications. However, the efficient collection and separation of charge carriers at the organic/Si heterojunction interface are primarily hindered by the inadequate work function of poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). Here, the application of a high-work-function MoO3 film onto the n-Si/PEDOT:PSS surface leads to a notable enhancement in the device's built-in potential. This enhancement results in the creation of an inversion layer near the n-Si surface and facilitates charge separation at the interface. Simultaneously, it inhibits charge recombination at the heterojunction interface. As a result, the champion PEDOT:PSS/Si solar cell, which incorporates a MoO3 interface layer, demonstrates an efficiency of 16.0% and achieves a high fill factor of 80.8%. These findings provide a straightforward and promising strategy for promoting the collection and transmission of charge carriers at the interface of photovoltaic devices.

Interlayer Charge Transition and Broadband Polarization Photodetection and Imaging Based on In2Se3/ReS2 van der Waals Heterostructure

Abstract2D van der Waal (vdWs) heterostructures present unique optoelectronic characteristics, making them favorable layer structures for constructing promising optoelectronic devices with multifunctional applications. Nevertheless, as a result of significant interface recombination of the photogenerated electron‐hole pairs and the presence of various absorption edges within constituent layers, they are prone to experiencing low carrier collection efficiency. In this work, a combined theoretical and experimental investigation are presented on the In2Se3/ReS2 vdWs heterostructure, aimed at developing high‐performance and broadband photodetector with multifunctionalities. In theoretical investigations, it is observed that, by adjusting the polarization states (+P to −P) in the In2Se3 layer, band alignment can be effectively tuned from type‐I to type‐II, providing a narrow bandgap of ≈0.65 eV, which is beyond that of their individual constituents. As a photodetector, the device shows broadband photoresponse ranging from 532 to 1550 nm with ultrahigh responsivity (99.36 AW−1), detectivity (3.5 × 1013 Jones), and external quantum efficiency (34195%). Additionally, competitive polarization sensitivity across the broad spectrum and imagining capability are observed with In2Se3/ReS2 vdWs heterostructure. This study demonstrates that In2Se3/ReS2 vdWs heterostructure device provides a promising technique for developing high‐performance 2D optoelectronic devices with multifunctionalities.

Covalent Heteroepitaxy of Large‐Area Vertical Hexagonal Boron Nitride for High‐Temperature VUV Photodetectors

AbstractHexagonal boron nitride (h‐BN) is a van der Waals (vdW) ultrawide bandgap semiconductor with high band‐edge absorption coefficient and chemical/thermal resistance, demonstrating great potential for vacuum ultraviolet (VUV) and UV‐C detection. Hitherto, most of their prevailing applications have exploited epitaxial films and multilayers either grown on substrates or transferred, which tend to form energy‐favorable noncovalent vdW epitaxy. Here, an alternative heteroepitaxy of 2‐inch h‐BN is reported with desirable thickness and vertically aligned vdW layers covalently bonded to sapphire, enabled by activating the inert substrate surface using ion impingement during deposition and the dislocation‐mediated epitaxial transition. The fabricated photodetectors allow efficient photon absorption and carrier collection using a simple planar device design, showing excellent VUV/UV‐C detection performance with ultrafast response of 270 ns/60 µs (rise/decay) and remarkable operating stability until 500 °C. This covalent heteroepitaxy of wafer‐scale h‐BN opens new avenues for optoelectronics and electronics significant to harsh environment applications.

Luminescence efficiency and carrier dynamics for InGaAs/GaAs surface quantum dots in coupled heterostructures

InGaAs/GaAs surface quantum dot (SQD) heterostructures have long been viewed as having great potential for realizing environmental gas detection devices. The research has recently been steered into discovering ways to inject carriers into the available SQD energy states to facilitate readable devices. In the present research, carrier injection from buried QDs (BQDs) to SQDs was controlled by changing the interlayer coupling. Photoluminescence (PL) measurements show that, by increasing the stacking period of BQDs, the carrier collection efficiency and subsequently the luminescence intensity for SQDs can be effectively improved. A rate equation simulation of the carrier recombination process is used to quantitatively describe the luminescent quantum efficiency (IQE) for the SQDs, indicating an increase with additional BQD layers due to an increase in carrier injection. The PL spectra along with the rate equation simulations further indicated that for these SQD hybrid structures nonradiative recombination dominates, with Auger recombination becoming significant at high excitation intensities. These results may help to understand the carrier dynamics in coupled SQDs hybrid structures. In addition, they provide a path to manipulating the properties of InGaAs SQDs for the development of gas sensors.

Simultaneous Band Alignment Modulation and Carrier Dynamics Optimization Enable Highest Efficiency in Cd‐Free Sb2Se3 Solar Cells

AbstractAntimony selenide (Sb2Se3) has developed as an eco‐friendly photovoltaic candidate owing to its non‐toxic composition and exceptional optoelectronic properties. However, the toxic and parasitic light‐absorbing CdS are widely used as electron transport layer (ETL) in Sb2Se3 solar cells, which severely limits its development. Herein, an alternative, zinc tin oxide (ZTO) ETL with varying composition‐dependent energy structure is deposited by atomic layer deposition (ALD) technique and used for constructing Cd‐free Sb2Se3 solar cells. It has been found that the ZTO ETL possessing an appropriate Zn/Sn ratio can alter the Sb2Se3/ZTO heterojunction band alignment to an ideal “spike‐like” arrangement. It not only suppresses the accumulation and recombination of charge carriers at the interface, but also effectively enhances carrier transport. In addition, thanks to the formation of passivated Sb2O3 ultra‐thin layer upon ALD process, the non‐radiative recombination within bulk Sb2Se3 can be effectively suppressed, and therefore enhancing carrier lifetime, extraction efficiency, and collection efficiency. Consequently, the as‐fabricated Mo/Sb2Se3/ZTO/ITO/Ag thin‐film solar cell demonstrates an impressive efficiency of 8.63%. This accomplishment establishes it as the most efficient Cd‐free Sb2Se3 solar cell to date, underscoring the significant advantages of incorporating ZTO ETL in the development of Sb2Se3 photovoltaic scenarios.

Cu2ZnSn(S,Se)4 solar cells with over 10% power conversion efficiency enabled by dual passivation strategy

Interfaces quality have always been considered the key factors in the fabrication of efficient Cu2ZnSn(S,Se)4 (CZTSSe) solar cells, and harmful defects at the interface can significantly reduce the performance of the device. Here, we propose a dual passivation strategy by adding Na to the surface of the absorber layer (CZTSSe) to passivate the CZTSSe/CdS interface and treating the buffer layer (CdS) using ultraviolet (UV) irradiation to passivate the CdS/ZnO interface. Due to the Na doping passivation, the absorber surface conductivity increases while the roughness decreases and detrimental defects that can lead to nonradiative recombination are reduced. The power conversion efficiency (PCE) of the cell is improved by about 1 percentage point by Na passivation. The contributions of open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) to the improvement of PCE have been quantified as 50.64%, −5.58%, and 54.94%, indicating that Na doping can significantly boost Voc and FF. UV-ozone passivation reduces residual carbon organics in the CdS buffer layer, weakens carrier recombination, allows for more light absorption, and widens the depletion region, which favors efficient carrier collection. The estimated contribution of Voc, Jsc, and FF to the PCE of the device is 8.78%, 119.59%, and −28.37%, respectively, demonstrating that UV-ozone passivation can significantly improve the Jsc of the device. The two passivation strategies complement each other's advantages and achieve a synergistic effect. Our prepared champion device exhibits a PCE of 10.69% and remarkable long-term stability.

Enhancing carrier collection in CsPbBr3 solar cells through crystal orientation and defect passivation

All-inorganic carbon-based CsPbBr3 perovskite solar cells (PSCs) have gained growing interest for their remarkable stability. However, compared to their organic–inorganic hybrid counterparts, there is still substantial room for improving their performance primarily due to the inferior photogenerated carrier collection efficiency. Here, we employ area-dependent transient photocurrent to assess the carrier transit time in CsPbBr3 PSCs, revealing that an extended carrier transit time relative to the lifetime significantly contributes to their low carrier collection efficiency. To address this challenge, we narrow the gap between carrier transit time and lifetime by introducing a dual-functional additive, serving to facilitate both crystallization orientation and defect passivation. Consequently, we achieve enhanced short-circuit current and efficiency in CsPbBr3 PSCs.

Suppressing interface recombination via element diffusion regulation towards high-efficiency Cd-free Cu(In,Ga)Se2 solar cells

Magnetron-sputtered Zn1-xMgxO (ZMO) films suffer from severe elemental diffusion to Cu(In,Ga)Se2 (CIGS), which limits the further improvement of device performance. Herein, we introduced Zn(O,S) (ZOS) as a barrier layer, and we controlled the diffusion of Zn within an appropriate range by adjusting the annealing temperature of ZOS. The results indicate that Zn can occupy copper vacancies (VCu) in CIGS and easily diffuse through VCu. A moderate amount of Zn at the interface acts as a charge compensator, reducing the band tailing effect and promoting the carrier collection efficiency of photovoltaic (PV) devices. However, excessive Zn doping induces additional defects dominated by ZnCu, ZnGa and ZnIn, leading to severe nonradiative recombination. Consequently, the Cd-free CIGS solar cell produced based on these insights exhibited a 49.4-mV reduction in the Voc deficit (Voc,def) as well as a notable increase in the power conversion efficiency (PCE) to 18.0 %. This study is the first to reveal the mechanism of defects caused by Zn diffusion, and these findings provide theoretical support for the study of Cd-free thin-film solar cells.

Optical design and bandgap engineering in ultrathin multiple quantum well solar cell featuring photonic nanocavity

AbstractUltrathin solar cells are efficient and captivating devices with unique technological and scientific features in terms of minimal material consumption, fast fabrication processes, and good compatibility with semi‐transparent applications. Such photovoltaic (PV) technologies can enable effective synergy between optical and electronic confinements with large tuning capabilities of all the optoelectronic characteristics. In this work, the implications of the optical design and the bandgap engineering in ultrathin hydrogenated amorphous Si/Ge multiple quantum well (MQW) solar cells featuring photonic nanocavity are analyzed based on experimental measurements and optoelectronic modelling. By changing the period thicknesses and the positions of QWs inside the deep‐subwavelength nanophotonic resonator, the spatial and spectral distributions of the optical field and the local absorption are strongly affected. This leads to a modulation of the absorption resonance condition, the absorption edge and the resulting photocurrent outputs. Because of quantum confinement effect, the change of MQW configurations with different individual QW periods while keeping similar total thickness of about 20 nm alters both the bandgap energy and the band offset at the QW/barrier heterojunctions. This in turn controls the photovoltage as well as the carrier collection efficiency in solar cells. The highest open circuit voltage and fill factor values are achieved by employing MQW device configuration with 2.5 nm‐thin QWs. A record efficiency above 5.5% is reached for such emerging ultrathin Si/Ge MQW solar cell technology using thinner QWs with sufficient number, because of the optimum trade‐off between all the optoelectronic characteristic outputs. The presented design rules for opaque ultrathin solar cells with quantum‐confined nanostructures integrated in a photonic nanocavity can be generalized for the engineering of relevant multifunctional semitransparent PV devices.

Ultrasensitive Near-Infrared Polarization Photodetectors with Violet Phosphorus/InSe van der Waals Heterostructures.

Near-infrared (NIR) polarization photodetectors with two-dimensional (2D) semiconductors and their van der Waals (vdW) heterostructures have presented great impact for the development of a wide range of technologies, such as in the optoelectronics and communication fields. Nevertheless, the lack of a photogenerated charge carrier at the device's interface leads to a poor charge carrier collection efficiency and a low linear dichroism ratio, hindering the achievement of high-performance optoelectronic devices with multifunctionalities. Herein, we present a type-II violet phosphorus (VP)/InSe vdW heterostructure that is predicted via density functional theory calculation and confirmed by Kelvin probe force microscopy. Benefiting from the type-II band alignment, the VP/InSe vdW heterostructure-based photodetector achieves excellent photodetection performance such as a responsivity (R) of 182.8 A/W, a detectivity (D*) of 7.86 × 1012 Jones, and an external quantum efficiency (EQE) of 11,939% under a 1064 nm photon excitation. Furthermore, the photodetection performance can be enhanced by manipulating the device geometry by inserting a few layers of graphene between the VP and InSe (VP/Gr/InSe). Remarkably, the VP/Gr/InSe vdW heterostructure shows a competitive polarization sensitivity of 2.59 at 1064 nm and can be integrated as an image sensor. This work demonstrates that VP/InSe and VP/Gr/InSe vdW heterostructures will be effective for promising integrated NIR optoelectronics.

Modeling the current-voltage characteristics of Sb2Se3 thin film solar cells through Sah-Noyce-Shockley recombination model

This study investigates the impact of various material parameters, such as film resistivity, the thickness of the absorber layer, uncompensated acceptor density, and carrier lifetime, on the carrier transport and device characteristics of emerging CdS/Sb2Se3 thin-film solar cells. The modeling approach is based on the rigorous Sah-Noyce-Shockley recombination model at the PN-junction, which is based on drift and diffusion collection efficiencies for total current-density calculations. The current-density and voltage have been optimized against the Sb2Se3 thickness and the depletion width at the CdS/Sb2Se3 junction. It has been determined that the lower efficiency of the cell is primarily due to the relatively short electron lifetime and the uncompensated acceptor density, which can widen or narrow the depletion width. The resistivity of the Sb2Se3 film can effectively control the voltage of the cell, however, the carrier lifetime can control this impact even to a higher extent. Therefore, the carrier lifetime and uncompensated acceptor densities are the two interdependent parameters that significantly control the current, voltage, and efficiency of the Sb2Se3 solar cells. This research provides valuable insights for the design and optimization of Sb2Se3 thin-film solar cells shedding light on carrier transport and charge collection mechanism in these emerging materials.

Universal growth of perovskite thin monocrystals from high solute flux for sensitive self-driven X-ray detection

Metal-halide perovskite thin monocrystals featuring efficient carrier collection and transport capabilities are well suited for radiation detectors, yet their growth in a generic, well-controlled manner remains challenging. Here, we reveal that mass transfer is one major limiting factor during solution growth of perovskite thin monocrystals. A general approach is developed to overcome synthetic limitation by using a high solute flux system, in which mass diffusion coefficient is improved from 1.7×10–10 to 5.4×10–10 m2 s–1 by suppressing monomer aggregation. The generality of this approach is validated by the synthesis of 29 types of perovskite thin monocrystals at 40–90 °C with the growth velocity up to 27.2 μm min–1. The as-grown perovskite monocrystals deliver a high X-ray sensitivity of 1.74×105 µC Gy−1 cm−2 without applied bias. The findings regarding limited mass transfer and high-flux crystallization are crucial towards advancing the preparation and application of perovskite thin monocrystals.

Metamaterial Engineering for Superior HgTe cQD Photodetector Performance

AbstractHighly responsive, low noise, and inexpensive photodetectors that operate in the mid‐infrared (MIR) wavelength regime are in high demand for applications ranging from fundamental science to large scale industries. However, simultaneously achieving all this in one device architecture is very challenging. In this work, mercury telluride (HgTe) colloidal quantum dot (cQD) based photodetectors are systematically improved by the introduction of new metamaterial designs. The new designs are found by utilizing simulations. Thereby the structures are optimized to increase the responsivity and simultaneously decrease the noise spectral current density. This is achieved by focusing on improving the photogenerated charge carrier collection efficiency while reducing the active material volume without altering the near unity absorption. A standard metamaterial perfect absorber architecture based on disc resonators is used as a starting point for the optimization process. By optimizing the carrier extraction through contact engineering, resulting in a narrow slot metamaterial, an overall ≈13‐fold responsivity and ≈345‐fold detectivity increase is achieved. The final metamaterial design reaches a responsivity of 16.2 A W−1 and detectivity of 6×108 Jones at a wavelength of 2710 nm. The analysis therefore provides a route to improve the responsivity and noise characteristics of mid‐infrared photodetectors based on cost‐efficient colloidal quantum dots.