Low-cost uncooled MWIR PbSe quantum dots photodiodes

McDowell L.L., Qiu J., Weng B., Shi Z.

In this work, we introduce the growth of a new complex oxide lead oxy-chalcogenide (PbOxSe1–x) thin film using an oxygen plasma-assisted molecular beam epitaxy method. Freshly cleaved BaF2(111) wafers were used as the substrates for this growth study. Systematic characterization of X-ray diffraction peaks, Raman shifts, absorption spectra, scanning electron microscopic imaging, and Hall measurements were conducted to elucidate the structural, optical, and electric properties of the as-grown PbOxSe1–x thin films. Specifically, X-ray diffraction measurements revealed that PbOxSe1–x films maintained the same rock-salt crystal structure as the PbSe semiconductor, but a slight shift in the lattice parameter was observed. A blue shift in the optical absorption edge also suggests that the inclusion of oxygen atoms led to the formation of a ternary compound crystal structure. Furthermore, all PbOxSe1–x thin films were observed to be polycrystalline in nature and displayed preferred [100] orientated grains. Slight...

Zhu T., Zheng L., Yao X., Liu L., Huang F., Cao Y., Gong X.

Broadband photodetectors have important applications in both scientific and industrial sectors. In this study, we report room-temperature-operated solution-processed photodetectors by PbSe quantum dots (QDs) with spectral response from 350 to 2500 nm. In order to boost both external quantum efficiency (EQE) and projected detectivity ( D*), the hole-trap-assisted photomultiplication effect through the EDT-PbSe QD/TABI PbSe QD double-thin-layer thin film, where EDT-PbSe QDs are 1,2-ethanedithiol (EDT)-capped PbSe QDs and TABI-PbSe QDs are tetrabutylammonium (TABI)-capped PbSe QDs, is applied. To further enhance D*, a thin layer of the conjugated polyelectrolyte, which offers significant hole injection resistance for suppressing dark current but enhancing photocurrent under illumination due to the photoinduced self-doping process, is applied for reengineering the electron extraction layer in PbSe QD-based photodetectors. As a result, at room temperature, PbSe QD-based photodetectors exhibit over 450% EQE and over ∼1012 Jones D* in the visible region and over 120% EQE and D* ∼4 × 1011 Jones in the infrared region. These results demonstrate that our studies provide a simple approach to realize room-temperature-operated solution-processed broadband photodetectors.

Shi X., Phan Q., Weng B., McDowell L.L., Qiu J., Cai Z., Shi Z.

Qiu J., Weng B., Ge W., McDowell L.L., Cai Z., Shi Z.

In this paper we have presented a power conversion efficiency (PCE) enhanced Pb-chalcogenide/CdS quantum dots (QDs) solar cells with novel tandem absorption layers synthesized by using chemical bath deposition (CBD) method. The tandem absorption layer is assembled by orderly stacking PbS-QDs layer, PbS-QDiM layer and PbSe-QDiM layer. Compared to single layer PbS-QDs/CdS solar cells, the solar cell with double-tandem layers (PbS-QDiM/QDs) shows the highest short current density ( J sc ) of 47.5 mA/cm 2 due to smoothing of the photo-generated carrier transportation and enhancing the absorption in the visible region 530–800 nm. However, the decreased open circuit voltage (V oc ) of 0.14 eV results in a low power conversion efficiency (PCE) of 2.2%. The triple-tandem absorber (PbSe-QDiM/PbS-QDiM/QDs) enhances the spectra absorption both in the visible (500–800 nm) and near-infrared (1000–1700 nm) regions, resulting in a higher short current density ( J sc ) of 40 mA/cm 2 , while keeping a relatively large open circuit voltage (V oc ) of 0.28 eV. Through an architectural modification, an enhancement of power conversion efficiency (PCE) of 4.2% has been achieved.

Xing X., Lei Y., Shang W., Du L., Guo P.

To improve the precision and sensitivity of the detection in near infrared gas detection system, the selection of light source and design of gas chamber structure are two key links. In this paper, the near infrared (NIR) light sources fabricated with PbSe quantum dots (QDs) and a new gas cell structure using an ellipsoid reflector were designed to test the concentration of methane (CH4). The double wavelengths differential detection method was used in the paper. The signal wavelength is 1.665 μm from the NIR QD-based light source with 5.1 nm PbSe QDs. The reference wavelength is 1.943 μm from the NIR QD-based light source with 6.1 nm PbSe QDs. The experimental results show that the differential gain signal could be enhanced 80 times when the major axis, the focus, and the open length of the ellipsoid reflector are 4.18 cm, 3.98 cm, and 0.36 cm, respectively. The structure will be convenient for the signal amplifying, AD converting, and other process in the latter circuits, and therefore both the detection sensitivity and precision can be improved.

Thambidurai M., Jang Y., Shapiro A., Yuan G., Xiaonan H., Xuechao Y., Wang Q.J., Lifshitz E., Demir H.V., Dang C.

The strong quantum confinement effect in lead selenide (PbSe) colloidal quantum dots (CQDs) allows to tune the bandgap of the material, covering a large spectral range from mid- to near infrared (NIR). Together with the advantages of low-cost solution processability, flexibility and easy scale-up production in comparison to conventional semiconductors especially in the mid- to near infrared range, PbSe CQDs have been a promising material for infrared optoelectronic applications. In this study, we synthesized monodisperse and high purity PbSe CQDs and then demonstrated the photodetectors working at different wavelengths up to 2.8 µm. Our high quality PbSe CQDs show clear multiple excitonic absorption peaks. PbSe CQD films of different thicknesses were deposited on interdigitated platinum electrodes by a simple drop casting technique to make the infrared photodetectors. At room temperature, the high performances of our PbSe CQD photodetectors were achieved with maximum responsivity, detectivity and external quantum efficiency of 0.96 A/W, 8.13 × 109 Jones and 78% at 5V bias. Furthermore, a series of infrared LEDs with a broad wavelength range from 1.5 μm to 3.4 μm was utilized to demonstrate the performance of our fabricated photodetectors with various PbSe CQD film thicknesses.

Wang Y., Bai X., Wang T., Yan L., Zhang T., Zhang Y., Yu W.W.

Recently, near-infrared light-emitting diodes (NIR LEDs) based on PbSe quantum dots (QDs) have attracted considerable attention due to their facilely tunable emission wavelength, as well as high quantum yield. However, the low external quantum efficiency (EQE) of these LEDs has restricted their actual applications because of the non-radiative recombination caused by the aggregation in the solid-state QD films. Therefore, we proposed in this work to employ the liquid-type structure in NIR LEDs base on PbSe QDs, which exhibited the main advantages relying on the fact that the liquid structure could prevent the active layer from self-aggregation and improve the device stability. The emission intensity of these NIR LEDs was optimized by tuning the concentration of PbSe QDs. Besides, the radiation power of PbSe QD-based devices with different emission wavelengths was analyzed under different biases, and the maximum EQE of NIR LEDs was confirmed to be 5.3%. This result represents the highest record among the reported NIR QD-LEDs, indicating this kind of liquid-type NIR LEDs is promising for commercial applications.

Sulaman M., Yang S., Bukhtiar A., Fu C., Song T., Wang H., Wang Y., Bo H., Tang Y., Zou B.

Narrow band-gap colloidal quantum dots (CQDs) are promising materials for flexible electronic, such as infrared light photodetectors and solar cells.

Chuai Y., Wang X., Zheng C., Zhang Y., Shen H., Wang Y.

We fabricated a series of infrared (IR)-transparent and conductive Sn-doped CuScO2 thin films using a polymer-assisted deposition (PAD) method.

Gao J., Fidler A.F., Klimov V.I.

In carrier multiplication, the absorption of a single photon results in two or more electron–hole pairs. Quantum dots are promising materials for implementing carrier multiplication principles in real-life technologies. So far, however, most of research in this area has focused on optical studies of solution samples with yet to be proven relevance to practical devices. Here we report ultrafast electro-optical studies of device-grade films of electronically coupled quantum dots that allow us to observe multiplication directly in the photocurrent. Our studies help rationalize previous results from both optical spectroscopy and steady-state photocurrent measurements and also provide new insights into effects of electric field and ligand treatments on multiexciton yields. Importantly, we demonstrate that using appropriate chemical treatments of the films, extra charges produced by carrier multiplication can be extracted from the quantum dots before they are lost to Auger recombination and hence can contribute to photocurrent of practical devices. In semiconductors, the absorption of a high energy photon can result in the formation of several charge pairs. Here the authors perform ultrafast photocurrent measurements on thin films to explore how quantum dot couplings and the electric field influence multiexciton photovoltaic devices.

Carey G.H., Abdelhady A.L., Ning Z., Thon S.M., Bakr O.M., Sargent E.H.

Graham H. Carey,† Ahmed L. Abdelhady,‡ Zhijun Ning, Susanna M. Thon, Osman M. Bakr,‡ and Edward H. Sargent*,† †Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Road, Toronto, Ontario M5S 3G4, Canada ‡Division of Physical Sciences and Engineering, Solar & Photovoltaics Engineering Center, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia School of Physical Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States

Zhang X., Zhang Y., Yan L., Ji C., Wu H., Wang Y., Wang P., Zhang T., Wang Y., Cui T., Zhao J., Yu W.W.

Thin PbSe nanocrystal active layer solar cells demonstrate a high photocurrent of 32.2 mA cm−2.

Sachet E., Shelton C.T., Harris J.S., Gaddy B.E., Irving D.L., Curtarolo S., Donovan B.F., Hopkins P.E., Sharma P.A., Sharma A.L., Ihlefeld J., Franzen S., Maria J.

The interest in plasmonic technologies surrounds many emergent optoelectronic applications, such as plasmon lasers, transistors, sensors and information storage. Although plasmonic materials for ultraviolet–visible and near-infrared wavelengths have been found, the mid-infrared range remains a challenge to address: few known systems can achieve subwavelength optical confinement with low loss in this range. With a combination of experiments and ab initio modelling, here we demonstrate an extreme peak of electron mobility in Dy-doped CdO that is achieved through accurate ‘defect equilibrium engineering’. In so doing, we create a tunable plasmon host that satisfies the criteria for mid-infrared spectrum plasmonics, and overcomes the losses seen in conventional plasmonic materials. In particular, extrinsic doping pins the CdO Fermi level above the conduction band minimum and it increases the formation energy of native oxygen vacancies, thus reducing their populations by several orders of magnitude. The substitutional lattice strain induced by Dy doping is sufficiently small, allowing mobility values around 500 cm2 V−1 s−1 for carrier densities above 1020 cm−3. Our work shows that CdO:Dy is a model system for intrinsic and extrinsic manipulation of defects affecting electrical, optical and thermal properties, that oxide conductors are ideal candidates for plasmonic devices and that the defect engineering approach for property optimization is generally applicable to other conducting metal oxides. The study of the electronic, thermal and optical properties of dysprosium-doped cadmium oxide reveals high electron mobility, rendering the material suitable for plasmonic applications in the mid-infrared region.

Yan L., Zhang Y., Zhang T., Feng Y., Zhu K., Wang D., Cui T., Yin J., Wang Y., Zhao J., Yu W.W.

Multigas sensing is highly demanded in the fields of environmental monitoring, industrial production, and coal mine security. Three near-infrared emission wavelengths from PbSe quantum dots (QDs) were used to analyze the concentration of three gases simultaneously through direct absorption spectroscopy, including acetylene (C2H2), methane (CH4), and ammonia (NH3). The corresponding lower detection limits for the three gases were 20, 100, and 20 ppm, respectively, with an accuracy of 2%. This study demonstrates that QDs with tunable emissions have great potential for simultaneous and uninterfered multiplex gas analysis and detection due to the advantages of the easy tunability of multiplex emitting wavelengths from QDs.

Zhang J., Gao J., Church C.P., Miller E.M., Luther J.M., Klimov V.I., Beard M.C.

Colloidal quantum dots (QDs) are promising candidates for the next generation of photovoltaic (PV) technologies. Much of the progress in QD PVs is based on using PbS QDs, partly because they are stable under ambient conditions. There is considerable interest in extending this work to PbSe QDs, which have shown an enhanced photocurrent due to multiple exciton generation (MEG). One problem complicating such device-based studies is a poor stability of PbSe QDs toward exposure to ambient air. Here we develop a direct cation exchange synthesis to produce PbSe QDs with a large range of sizes and with in situ chloride and cadmium passivation. The synthesized QDs have excellent air stability, maintaining their photoluminescence quantum yield under ambient conditions for more than 30 days. Using these QDs, we fabricate high-performance solar cells without any protection and demonstrate a power conversion efficiency exceeding 6%, which is a current record for PbSe QD solar cells.

Yu L., Tian P., Liang K.

Colloidal quantum dots (QDs) have emerged as promising materials for the development of infrared photodetectors owing to their tunable band gaps, cost-effective manufacturing, and ease of processing. This paper provides a comprehensive overview of the fundamental properties of quantum dots and the operating principles of various infrared detectors. We review the latest advancements in short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) detectors employing colloidal quantum dots. Despite their potential, these detectors face significant challenges compared to conventional infrared technologies. Current commercial applications are predominantly limited to the near-infrared and short-wave bands, with medium- and long-wave applications still under development. The focus has largely been on lead and mercury-based quantum dots, which pose environmental concerns, underscoring the need for high-performance, non-toxic materials. Looking forward, the development of large array and small pixel detectors and improving compatibility with readout circuits are critical for future progress. This paper discusses these hurdles and offers insight into potential strategies to overcome them, paving the way for next-generation infrared sensing technologies.

Rastkar Mirzaei M., Shi Z.

Room-temperature (RT) high-performance mid-wavelength infrared (MWIR) Lead Selenide (PbSe)/Cadmium Selenide (CdSe) heterostructure nanocrystal photoconductors are designed and fabricated on commercial silicon dioxide on silicon (SiO2/Si) wafer via vapor phase deposition. Tunable absorption edges at 3.75 and 4.0 μm are demonstrated with different sizes of the nanostructure. The devices are annealed in oxygen to make the thin film much more sensitive to MWIR light. The detectors are etched by the reactive ion etching method to define an active area of 17.5 × 20 μm2. All devices exhibit external quantum efficiencies exceeding 100%, a clear indication of photoconductive gain. 1/f noise is the dominating noise source, and it follows Hooge's empirical relation for a homogeneous semiconductor. RT peak specific detectivity (D*) of 2.17 × 1010 and 1.61 × 1010 Jones is achieved for pixels with absorption edge at 3.75 and 4 μm, respectively.

Ponomarenko Vladimir P., Popov Victor, Shuklov Ivan, Ivanov Victor V., Razumov Vladimir F.

Photosensing based on colloidal quantum dots (CQDs) is a rapidly developing area of infrared photoelectronics. The use of colloidal quantum dots markedly simplifies the manufacture, decreases the restrictions to the pixel pitch of the photosensitive elements, and reduces the production cost, which facilitates the wide use of IR sensors in various technological systems. This paper is the first exhaustive overeview of the architectures, methods of manufacturing and basic properties of photonic sensors based on colloidal quantum dots of compounds of Group II, IV and VI elements. Characteristic features of the synthesis and roles of the ligands and CQD morphology in the design of photosensors are considered in detail. The structures of photoresistive, photodiode and phototransistor elements based on HgTe, HgSe, PbS and PbSe CQDs, which are sensitive in various spectral ranges, are described. The main parameters of the most advanced optoelectronic devices based on colloidal quantum dot structures are presented. The key trends in the development of this area are analyzed.The bibliography includes 361 references.

Fu Y., Zhang G., Tang H., Yang Y., Qiu J.

Enhancing the detectivity is still a challenge for uncooled mid-infrared PbSe photoconductive (PC) detectors. Antireflection coating (ARC) provides a convenient solution to this challenge. Herein, antireflection physical modeling was proposed based on microstructural features of PbSe PC detectors. The simulated results show that the surface roughness contributes to the absorption enhancement of PbSe detectors, which reflects the advantage of the chemical bath deposition (CBD) manufacturing technology. Meanwhile, being the optimal ARC choice, ZnS ARC with thickness from 300 to 420 nm could induce more than 20 % absorption improvements in coarse CBD-PbSe films, which is confirmed by a signal enhancement from CBD-PbSe PC detectors covered with ZnS ARC. Combing with a noise reduction, the peak detectivity (D*) is almost doubled from 0.8 × 1010 to 1.5 × 1010 cm‧Hz1/2‧W−1 after depositing a desired ZnS ARC. Furthermore, ZnS ARC significantly eliminates the performance degradation of detectors triggered by moisture in the air. The low-cost ZnS ARC with good repeatability, which combines the characteristics of antireflection and passivation, provides an available solution to promote the industrialization of PbSe PC detectors.

Qiu J., Su L., McDowell L.L., Phan Q., Liu Y., Zhang G., Yang Y., Shi Z.

Park J., Al Mahfuz M.M., Huebner R., Ko D.

Iqbal M.A., Malik M., Le T.K., Anwar N., Bakhsh S., Shahid W., Shahid S., Irfan S., Al-Bahrani M., Morsy K., Do H., Ponnusamy V.K., Pham P.V.

Liu Y., McDowell L.L., Su L., Luo Y., Qiu J., Shi Z.

High-quality lead selenide (PbSe) epitaxial films are key to improving the performance of mid-wave infrared (MWIR) optoelectronics. Herein, high-quality PbSe epitaxial films with 30 μm in thickness were successfully fabricated by chemical bath deposition (CBD), and the growth modes were described by investigating the effect of growth temperature and [OH − ]/[Pb 2+ ] on the morphologies and microstructural evolution of PbSe epitaxial films. Furthermore, a new pre-orientation induced oriented attachment (POIOA) growth mechanism was proposed to illustrate the texture of close-packed PbSe (111) nano-pyramids. It was found that the film orientation is determined by the epitaxial seed layer and the growth mechanism varies with temperature changing from the low-temperature cluster mechanism (LTCM, < 30 °C) to the middle-temperature POIOA (30–60 °C) mechanism, and finally dominated by high-temperature ion-by-ion (HTIBI, > 60 °C) which was crucial for single-crystal PbSe deposition. The increased [OH − ]/[Pb 2+ ] can significantly decrease the transformation-temperature of the growth mechanism, and the single-crystal film can be obtained as the temperature reaches 40 °C. Eventually, a microstructural zone model of films as a function of temperatures and [OH − ]/[Pb 2+ ] was established.

McDowell L.L., Qiu J., Mirzaei M.R., Weng B., Shi Z.

Heredia-Cancino J.A., Salcido O., Britto-Hurtado R., Ruvalcaba-Manzo S.G., Ochoa-Landín R., Castillo S.J.

Complete optoelectronic devices present major difficulties to be built by aqueous chemical deposition. In this work, a ITO/CdS/PbSe heterostructure was developed, depositing CdS over an ITO-coated substrate via a chemical bath deposition (CBD) technique. The next step involved the growth of a plumbonacrite film over CdS via CBD, where the film acted as a precursor film to be converted to PbSe via ion exchange. The characterization of each material involved in the heterostructure were as follows: the CdS thin films presented a hexagonal crystalline structure and bandgap of 2.42 eV; PbSe had a cubic structure and a bandgap of 0.34 eV. I vs. V measurements allowed the observation of the electrical behavior, which showed a change from an ohmic to diode response by applying a thermal annealing at 150 °C for 5 min. The forward bias of the diode response was in the order of 0.8 V, and the current-voltage characteristics were analyzed by using the modified Shockley model, obtaining an ideality factor of 2.47, being similar to a Schottky diode. Therefore, the reported process to synthesize an ITO/CdS/PbSe heterostructure by aqueous chemical methods was successful and could be used to develop optoelectronic devices.

Aleksandrova M.

An approach for optoelectronic infrared detection is demonstrated by combining conventional silicon technology, lead-free perovskite-type material, and quantum dots core–shell. It is shown that the device is sensitive to wavelengths in the infrared range of the electromagnetic spectrum up to 1055 nm. The detector is characterized by a high responsivity of 947 mA/W and fast response of 2.43 ms at 1055 nm. The detectivity and the external quantum efficiency at the same wavelength are found to be 5 × 107 Jones and 114%, respectively. This is considered as very good performance and can be ascribed to the presence of a photoelectric effect, producing a voltage that affects the silicon/IR material interface, controlling the depletion layer. It was found that the dark current varied between 1.2 nA and 8 nA in the temperature range of 10–40 °C and that the quantum dots coating contributes more to the dark current formation in comparison with the perovskite coating. Shallow traps were identified to present in the perovskite/quantum dots system. The impedance spectroscopy showed negligible parasitic capacitance and inductance, which cannot deteriorate the charge carrier transport and the response times of the proposed device. These results are a good initial step to further optimization of the lead-free perovskite-based optoelectronics realized with compatible silicon technology.

Qiu J., Liu Y., Zhang G., Shi K., Li Y., Luo Y.

The low detectivity of VPD-PbSe MIR detectors was broken by duplicating the microstructural features and phase composition of high-performance CBD-PbSe detectors, providing a commercial technical solution for megapixel uncooled PbSe FPA imagers.

Iram S., Mahmood A., Ehsan M.F., Mumtaz A., Sohail M., Sitara E., Mushtaq S., Malik M.A., Fatima S.A., Shaheen R., Ahmad N.M., Malik S.N.

This research endeavor aimed to synthesize the lead (II) diphenyldiselenophosphinate complex and its use to obtain lead selenide nanostructured depositions and further the impedance spectroscopic analysis of these obtained PbSe nanostructures, to determine their roles in the electronics industry. The aerosol-assisted chemical vapor deposition technique was used to provide lead selenide deposition by decomposition of the complex at different temperatures using the glass substrates. The obtained films were revealed to be a pure cubic phase PbSe, as confirmed by X-ray diffraction analysis. SEM and TEM micrographs demonstrated three-dimensionally grown interlocked or aggregated nanocubes of the obtained PbSe. Characteristic dielectric measurements and the impedance spectroscopy analysis at room temperature were executed to evaluate PbSe properties over the frequency range of 100 Hz–5 MHz. The dielectric constant and dielectric loss gave similar trends, along with altering frequency, which was well explained by the Koops theory and Maxwell–Wagner theory. The effective short-range translational carrier hopping gave rise to an overdue remarkable increase in ac conductivity (σac) on the frequency increase. Fitting of a complex impedance plot was carried out with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb), which proved that grains, as well as grain boundaries, are responsible for the relaxation processes. The asymmetric depressed semicircle with the center lower to the impedance real axis provided a clear explanation of non-Debye dielectric behavior.

Hafiz S.B., Al Mahfuz M.M., Lee S., Ko D.

As an emerging member of the colloidal semiconductor quantum dot materials family, intraband quantum dots are being extensively studied for thermal infrared sensing applications. High-performance detectors can be realized using a traditional p-n junction device design; however, the heavily doped nature of intraband quantum dots presents a new challenge in realizing diode devices. In this work, we utilize a trait uniquely available in a colloidal quantum dot material system to overcome this challenge: the ability to blend two different types of quantum dots to control the electrical property of the resulting film. We report on the preparation of binary mixture films containing midwavelength infrared Ag2Se intraband quantum dots and the fabrication of p-n heterojunction diodes with strong rectifying characteristics. The peak specific detectivity at 4.5 μm was measured to be 107 Jones at room temperature, which is an orders of magnitude improvement compared to the previous generation of intraband quantum dot detectors.

Choi K., Dutta A.K., Dhar N.K.

For mid-wave infrared detectors, we designed a meta-surface to enhance quantum efficiency (QE) across 2 to 6 microns. The relative enhancement depends on the intrinsic absorption coefficient α of the material. If α is large at 2×10 4 /cm, a 0.1 micron-thick meta-detector can yield a peak QE of 90%, which is 2.6 times higher than the conventional detector. The improvement is larger with a smaller α. When it is 2000/cm, the improvement is about 10 times with a peak QE of 49%. For energy harvesting devices, we designed several nanostructures etched on top of silicon solar cells to enhance their absorption. Employing an array of nano-columns increases absorption from 55% to 97% at 0.7 microns and from 5.0% to 37% at 1.0 microns. An array of nano-cones further increases the average absorption to 95% between 0.4 to 0.8 microns. The overall integrated absorption is increased by 74% for nano-columns and 92% for nano-cones. For GaAs solar cells, a metasurface can improve photocurrent by 26% from a planar solar cell with a 100 nm-thick absorber.