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Perovskite‐based tandem solar cells have demonstrated high potential for overcoming the Shockley–Queisser limit. Routine bandgap (RBG, ≈1.55 eV) perovskites have achieved a perfect balance between efficiency and stability. The narrow bandgap (NBG) candidates for RBG perovskite‐based tandem devices are very limited. Lead sulfide (PbS) colloidal quantum dots (CQDs) are a promising partner due to their broad absorption spectra. However, the efficiency of RBG perovskite/QD tandem devices still lags behind. Herein, efficient RBG perovskite/QDs four‐terminal tandem photovoltaics are successfully implemented through synergistic enhancement from transparent electrode and band alignment Engineering. For tin doped indium oxide (ITO) electrodes, their conductivity and near‐infrared transparency are leveraged using magnetron sputtering and reactive plasma deposition (RPD) methods. Furthermore, instead of traditional zinc oxide, aluminum‐doped zinc oxide (AZO) is developed to enhance the carrier extraction capability of PbS QD bottom cells. Based on the above enhancements, ≈0.95 eV PbS solar cells achieve a record efficiency of 14.14%. Integrated with the front semi‐transparent perovskite solar cells, the four‐terminal perovskite/QD tandem device reaches a record efficiency of 26.12%. The synergistic combination of the RBG perovskite and NBG QD devices provides promising prospects for tandem photovoltaics. [ABSTRACT FROM AUTHOR]

Stable luminance properties are essential for light-emitting devices with excellent performance. Thermal photoluminescence (PL) quenching of quantum dots (QDs) under a high temperature resulting from a surface hole or electron traps will lead to unstable and dim brightness. After treating CdZnSe/ZnSe QDs with TBP, which is a well-known passivation reagent of the anions, the excess Se sites on the surface of the QDs were removed and their PL quantum yields (QYs) was improved remarkable. Furthermore, after TBP treatment, the CdZnSe/ZnSe QDs exhibit no quenching phenomena even at a high temperature of 310°C. The electroluminescent light-mitting diodes based on the QDs with TBP treatment also demonstrated satisfied performance with a maximum current density of 1679.6 mA/cm2, a peak luminance of 89500 cd/m2, and the maximum values of EQE and luminescence efficiency are 15% and 14.9 cd/A, respectively. The performance of the fabricated devices can be further improved providing much more in-depth studies on the CdZnSe/ZnSe QDs. [ABSTRACT FROM AUTHOR]

Silicon quantum dots (Si-QDs) embedded B-doped SiN films were fabricated by magnetron co-sputtering. The effects of B content on the structural, optical and electrical properties of the films were studied. The study found that the amount of B dopant has no significant effect on the crystallization characteristics of the films. B atoms may be doped in the Si-QDs or exist in the silicon nitride or the interface between Si-QDs and the matrix. PL intensity increases with increasing B content, but increases at first and then decreases. The conductivity as a function of the dopant concentration increases at first from a value of 2.71 × 10 S/cm to 5.83 × 10 S/cm until 0.9 at.% and then decreases. By employing B-doped Si-QDs films, Si-QDs/c-Si heterojunction solar cells were fabricated and the effect of B doping concentration on the photovoltaic properties was studied. It was found that, with the increase of B doping amount, the photovoltaic performance is improved, when the B doping amount is 0.9 at.%, the efficiency reaches the highest value of 4.26%. [ABSTRACT FROM AUTHOR]

Growth of Sb/SiN multilayers, followed by high-temperature annealing, was shown to be an effective strategy for synthesizing Sb-doped Si quantum dots (Si-QDs). The doping concentration of Sb (from 0.32 at.% to 1.82 at.%) was controlled by varying the thickness of Sb sublayer. Moderate Sb concentrations were found to enhance the formation of Si-QDs. Photoluminescence (PL) results show that the nonradiative recombination defects caused by Sb impurities increased with the increase of Sb content, which leads to the decrease of the emission intensity. Hall measurements demonstrate that as the carrier concentration increases, the mobility of Hall decreases, and the conductivity increases at first and then decreases with the increase of Sb content. It is indicated that the excessive high Sb doping will deteriorate the conductive properties. The observed -type electrical behavior and great enhancement increase in conductivity of the Sb-doped Si-QDs film suggest an effective Sb doping. A - junction was formed between Sb-doped Si-QDs and a -type c-Si substrate, exhibiting good rectifying properties. [ABSTRACT FROM AUTHOR]

In this work, an effective strategy for the controlled synthesis of Si-QDs embedded Si-rich silicon oxide/SiO (SRO/SiO) multilayers using susceptor-assisted microwave annealing (MWA) is introduced. Both MWA and rapid thermal annealing (RTA) were compared to study the growth of Si-QDs embedded in SRO/SiO multilayers, and found that the temperature required for forming Si-QDs decreases by 200 °C under MWA. SRO single-layer films were used for the investigation of growth mechanism during MWA. It is shown that MWA annealing could enhance the phase separation in SRO films and more Si-QDs precipitated in SRO film annealed by MWA than RTA one. These results demonstrate that the microwave electromagnetic field has unique influence on the generated Si-QDs, can be considered as an archetype of a non-thermal microwave effect. [ABSTRACT FROM AUTHOR]

Under the condition of the fixed SiN layer thickness of 1.1 nm, Si-QDs embedded in B-doped SiN/SiN multilayer thin films with various SiN layer thickness were fabricated respectively. Si-QDs with controllable and nearly uniform size were formed in SiN layers, and found that the optical band gap of the films can be adjusted by changing the thickness of SiN layer. On the basis of this, the Si-QDs/c-Si heterojunction solar cells were prepared. It is found that the larger the band gap is, the higher the cell efficiency is. The best performance device is obtained with average QD size of ~3.5 nm, which has the highest efficiency of 7.05 % compared with the other two devices. This difference is caused by the difference of the spectral response of these devices. [ABSTRACT FROM AUTHOR]

Si/SiCO multilayers have been prepared by magnetron sputtering technique. Effects of annealing temperature ( T ) on the microstructural and electrical properties of Si/SiCO multilayer films were systematically investigated using high resolution transmission electron microscope, grazing incident X-ray diffraction, Raman spectroscopy, UV-Vis-NIR spectroscopy, and Hall measurements. The T has great effects on the optical properties of Si/SiCO multilayer thin films. It is found that the onset of nanocrystalline Si phase (Si quantum dots) formation occurs at 800 °C. SiC crystalline phases are not formed in Si/SiCO multilayer film even at the T 1000 °C. It is indicated that the method of depositing a Si/SiCO multilayer followed by thermal induced crystallization gives flexibility to suppress the crystallization of an a-SiC phase. With increasing T the grain size, dot density, and optical bandgap increase, the conductivity also increase. These results demonstrate that high quality Si QDs embedded in Si/SiCO multilayer films deposited by magnetron sputtering can be obtained by properly controlling the annealing condition. [ABSTRACT FROM AUTHOR]

Pursuit of an efficient strategy for quantum dot-sensitized photoanode has been a persistent objective for enhancing photovoltaic performances of quantum dot-sensitized solar cell (QDSC). We present here the fabrication of the indium sulfide (In 2 S 3 ) quantum dot-sensitized titanium dioxide (TiO 2 ) photoanode by combining successive ionic layer adsorption and reaction (SILAR) with solvothermal processes. The resultant QDSC consists of an In 2 S 3 sensitized TiO 2 photoanode, a liquid polysulfide electrolyte, and a Co 0.85 Se counter electrode. The optimized QDSC with photoanode prepared with the help of a SILAR method at 20 deposition cycles and solvothermal method yields a maximum power conversion efficiency of 1.39%. [ABSTRACT FROM AUTHOR]

Over the last few years silicon quantum dots (Si QDs) have come under intensive research because of their interesting physical properties and their potential use in future electronic and optoelectronic applications. Focusing on photovoltaic applications, we review recent progress in silicide-embedded Si QDs films with different fabrication techniques and different characteristics. Some avenues for further material improvements are discussed. The performances of several photovoltaic devices reported in the literature are also reviewed and discussed. We assess the state of the art in the area of Si QDs layer deposition, including fabrication technologies and film properties, and highlight the challenges that need to be overcome. Finally, some existing problems and future work are pointed out. [ABSTRACT FROM AUTHOR]

Si-rich silicon nitride (SRSN) (SiN, x ≈ 0.49) films were deposited on Si (100) and quartz substrates by magnetron co-sputtering. For comparison, two sets of identical samples were then treated in a nitrogen atmosphere by conventional rapid thermal processing (CRTP) and light-filtering rapid thermal processing (LRTP) at temperature in a range of 950-1,100 °C, respectively. Raman spectroscopy, grazing incident X-ray diffraction, transmission electron microscope, photoluminescence (PL) and Hall measurements were used to analyze the structure, luminescence, and conductivity of the films. Experimental results show that the samples treated with LRTP posses higher dot number density, crystalline volume fraction, PL intensity and conductivity than the CRTP samples. The quantum effects in rapid thermal processing have a negative influence on the formation and density of Si quantum dots (QDs) in SRSN films. The present work opens new strategy for the formation of high density Si QDs embedded in SRSN films. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells are regarded as promising candidates to resolve the energy and environmental issues in recent years, arising from their solution-processable fabrication technology and high power conversion efficiency. However, there are still several problems regarding how to accelerate the development of this type of photovoltaics, including the limited light-harvesting ability and high-production cost of molecular dye. In the current work, we have systematically studied the role of nitrogen-doped carbon quantum dots (N-CQDs) as co-sensitizers in traditional dye sensitized solar cells. A series of N-CQDs have been prepared by employing chitosan as a precursor via one-pot hydrothermal technology for various times, demonstrating a maximized efficiency as high as 0.089% for an only N-CQDs-based device. Moreover, the co-sensitized solar cell based on N719 dye (C58H86N8O8RuS2) and optimized N-CQDs shows significantly enhanced performance, yielding a solar-to-electric conversion efficiency of up to 9.15% under one standard sun (AM 1.5G) irradiation, which is much higher than the 8.5%-efficiency of the controlled device without N-CQDs. The matched characteristics of energy level, excellent up-convention, and FRET (Förster resonance energy transfer) abilities of N-CQDs are responsible for their improved power conversion efficiency. [ABSTRACT FROM AUTHOR]

Black phosphorus quantum dots (BPQDs) have recently obtained great attention due to their high mobility and tunable bandgap features, which are beneficial for their potential application in photoelectronic devices. However, a precise synthesis of high-quality BPQDs is still a great challenge owing to the formation of an impurity phase when employing traditional methods. Herein, we demonstrate the scalable fabrication of BPQDs from mineralization-derived bulk black phosphorus (BP) single crystals by means of a microwave (MW)-assisted liquid-phase exfoliation method in ethanol. The primary results demonstrate that ethanol plays a crucial role in determining the final properties of BPQDs, such as their excellent tolerance to oxygen, good crystallinity, and uniform size. Furthermore, the mechanism behind the formation of BPQDs is proposed, revealing that a layer-by-layer disintegration process of bulk BP crystals under microwave-energy stimuli is responsible. This work may provide a novel path for the further development of BPQDs and corresponding devices. [ABSTRACT FROM AUTHOR]

A correction is presented to the article "Size-controlled Si quantum dots embedded in B-doped SiNx/Si3N4 superlatice for Si quantum dot solar cells," by Xiaobo Chen and others, published in a 2017 issue.

Abstract Although organometal halide perovskites have garnered enormous interest as solution-processed absorbing layers in solar cells with power conversion efficiencies breaking 20%, nonetheless seldom effort has been made to light emitting devices fabricated from formamidinium lead halide perovskite quantum dots (QDs). Herein we demonstrate a facile and low-cost room-temperature synthesis of highly luminescent and color-tunable formamidinium lead halide perovskite QDs (FAPbX 3 , X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) using inexpensive commercial precursors. Through compositional engineering, the photoluminescence emission spectra are readily tunable in the range of 430–690 nm, covering most of the visible spectral region. The photoluminescence (PL) spectra of FAPbX 3 QDs are of the characteristics including narrow emission line-widths of 16–34 nm largely, high quantum yields (QYs) of as high as 88%, and radiative lifetimes in the range of 19.8–53.0 ns. Furthermore, FAPbBr 3 QDs exhibit single decay dynamics and nearly non-blinking at single-dot level have been observed. We also demonstrate the green light emitting diodes (LEDs) based on the as fabricated highly efficient perovskite QDs, which shows a high efficient luminance of 403 cd m−2, and a moderately high max external quantum efficiency (EQE) of 2.8% after optimizing the thickness of the perovskite QD layer. Additionally, the LEDs based on FAPbBr 3 QDs demonstrate good stability of emission peaks with increasing applied voltage. These results indicate that FAPbX 3 QDs have great potential application in lighting devices. Graphical abstract Here we have applied for the first time the modified nonaqueous emulsion synthesis approach to produce the highly luminescent FAPb(Br x X 1-x) 3 (X = Cl, Br, I) quantum dots (QDs) at room-temperature. The resulted FAPbBr 3 QDs deliver a photoluminescence (PL) maximum around 538 nm, a high PL quantum yield (QY) of about 88%, which is believed to be the highest one, and full-width of half-maximum (FWHM) of ∼22 nm. By varying the thickness of QD layers, we have demonstrated the highly efficient perovskite QD-based light emitting diodes (PLEDs) based on FAPbBr 3 QDs. Additionally, with the applied voltage increasing from 4 to 6 V, the peak location of the EL spectra of the PLEDs based on FAPbBr 3 QDs demonstrates good stability. These excellent results indicate that FaPbX 3 QDs have great potential application in lighting devices. Image 1 Highlights • Through compositional engineering, the photoluminescence spectra of FAPbX 3 QDs is readily tunable from 430 to 690 nm. • FAPbBr 3 QDs exhibit single decay dynamics and nearly no blinking at single-dot level. • EL spectra of the QLEDs based on FAPbBr 3 QDs demonstrate nearly no red-shift with increasing applied voltage. [ABSTRACT FROM AUTHOR]

• Composite MXene/CoS based CE is first time used in QDSSCs. • The novel MXene/CoS CE shows better charge transfer and catalytic properties.. • The QDSSC with MXene/CoS CE exhibit a high efficiency of 8.09%. • A better photovoltaic performance than most of reported similar composite CEs. Low electrocatalytic activity and/or high charge transfer resistance of counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSSCs) are the main reasons for the low photovoltaic performance. Herein, the CoS nanoparticles are anchored on the MXene (Ti 3 C 2 T x) via a simple in-situ hydrothermal reaction process. It is the first attempt to use the MXene/CoS as a highly electrocatalytic CE for QDSSCs. The QDSSCs with a MXene/CoS CE shows a significant enhancement in cell performances and yields a promising power conversion efficiency (PCE) of 8.09% compared with that of the QDSSCs with bare CoS (5.77%) and bare MXene (4.25%) CEs. The significant enhancement of PCE value is mainly attributed to the synergistic effects of the unique layered morphology of conductive MXene nanosheets and its cocatalysis with CoS nanoparticles. The coupling of layered MXene with small CoS nanoparticles (~15 nm) provides abundant catalytic active sites. The improved mesoporous morphology contributes a high specific surface area and fast electron transfer channels for S x 2− reduction. Consequently, the MXene/CoS nanocomposite can be utilized as an effective agent to boost up the photovoltaic performance of QDSSCs. [ABSTRACT FROM AUTHOR]

Pursuit of low-cost and large-scale method to prepare carbon quantum dots (CQDs) is a persistent objective in recent years. In this work, we have successfully synthesized a series of nitrogen-doped carbon quantum dots (N-CQDs) under different hydrothermal temperature employing Eichhornia crassipes (ECs) as precursors. Considering the pollution ability to water and low-cost, this study may direct the novel path to convert waste material to useful quantum dots. After measurements such as TEM, XRD, Raman, XPS, PL as well as the UV–vis absorbance ability, outstanding optical properties have been discovered. In this fashion, solar cells are tentative to be fabricated, yielding the maximized solar-to-electrical conversion efficiency of 0.17% with a good fill factor of 67%. Meanwhile, the above-mentioned quantum dots also show the up-conversion ability, suggesting the potential application in infrared detection or broadening light-absorbing devices. [ABSTRACT FROM AUTHOR]

A dual-mode fluorescent probe based on new carbon dots have good linear relationships with the polarity of solvents both in down-conversion luminescence and up-conversion luminescence (R 2 = 0.9909, 0.9374). [Display omitted] • Down-conversion and up-conversion luminescence based detection mode. • New carbon dots based on 1,10-phenanthroline for detecting solution polarity. • Good linear relationships for the polarity of solvents in two modes. Fluorescent probes always attract huge attention. In particular, carbon dots, due to their unique biocompatibility and variable fluorescence characteristics, can be used in multiple fields and were fulled of expectation by researchers. Since the advent of the dual-mode carbon dots probe, which greatly improved the accuracy of quantitative detection, there are higher hopes for dual-mode carbon dots probes. Herein, we have successfully developed a new dual-mode fluorescent carbon dots probe based on 1,10-phenanthroline (Ph-CDs). Ph-CDs detect the object to be measured based on both down-conversion luminescence and up-conversion luminescence at the same time, different from the reported dual-mode fluorescent probes which are based on the wavelength and intensity changes in down-conversion luminescence. As-prepared Ph-CDs have good linear relationships with the polarity of solvents in down-conversion luminescence (R 2 = 0.9909) and up-conversion luminescence (R 2 = 0.9374), respectively. Hence, Ph-CDs provide a new in-depth insight into the design of fluorescent probes with dual-mode detection and they can give more accurate, reliable and convenient detection results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PAMPS/NQDs with higher hole mobility and conductivity improves hole transport. • Modifying PAMPS/NQDs induced lower interfacial energy barrier boosts hole extraction. • The PAMPS/NQDs heals the defects of CsPbBr 3 film and enhances the hydrophobicity. • The unsealed device achieves a best PCE of 10.21% and excellent long-term stability. The regulation of the interface energetics and the simultaneous passivation of the surface defects of perovskite (PVK) film play an important role in improving the efficiency and stability of perovskite solar cells (PSCs). Here, a composite modification of poly(2-acrylamide-2-methylpropanesulfonic acid) (PAMPS)/NiFe 2 O 4 quantum dots (NQDs) that is formed by the light-triggered polymerization of AMPS monomer in homogeneous AMPS/NQDs is launched at the interface of PVK/carbon in all-inorganic CsPbBr 3 PSCs. Due to the higher hole mobility and conductivity of PAMPS/NQDs and its interface modification induced better energy level alignment and interfacial contact, the hole transport and extraction are significantly promoted. Combined with the simultaneous passivation of cations and anions (Cs+, Pb2+ and Br-) defects on CsPbBr 3 PVK surface by the S O, C O, N H and O H groups in PAMPS, the non-radiative recombination is effectively restrained, rendering a champion power conversion efficiency of 10.21 % with excellent high humidity and temperature (85 % RH, 85 °C) and light soaking tolerances for PAMPS/NQDs composite modified carbon-based CsPbBr 3 PSCs without encapsulation in air, which is markedly higher than the 6.81 % efficiency of the control device. [ABSTRACT FROM AUTHOR]

Pursuit of a high efficiency and stability has been a persistent objective for quantum dot-sensitized solar cells (QDSCs). Here we launch a strategy of synthesizing graphene implanted polyacrylamide (PAAm-G) conducting gel electrolytes for quasi-solid-state QDSCs. With an aim of elevating the dosage of S 2− /S x 2− redox couples and therefore charge-transfer ability, both osmotic press across the PAAm-G and capillary force within the three-dimensional micropores are utilized as driving forces. A promising power conversion efficiency of 2.34% is recorded for the QDSCs by optimizing graphene dosage in the conducting gel electrolyte. The enhanced conversion efficiency of solar cell is attributed to the expanded catalytic area from counter electrolyte/electrolyte interface to both interface and the conducting gel electrolyte. [ABSTRACT FROM AUTHOR]