Back-Contact Ionic Compound Engineering Boosting the Efficiency and Stability of Blade-Coated Perovskite Solar Cells.

Surface defect passivation, which plays a vital role in achieving high-efficiency perovskite solar cells (PSCs) in a spin-coating process, is rarely compatible with a printing process. Currently, printing PSCs with high efficiency remains a challenge, as only a few laboratories realized an efficiency of over 20%. In this work, zwitterionic compounds 2-hydroxyethyl trimethyl ammonium chloride (HETACl) and butyltrimethylammonium chloride (BTACl) were introduced, both of which can spontaneously adsorb on the surface perovskite and form an ultrathin passivation layer by a dip coating method.

F-Type Pseudo-Halide Anions for High-Efficiency and Stable Wide-Band-Gap Inverted Perovskite Solar Cells with Fill Factor Exceeding 84.

The quality of wide-band-gap (WBG) perovskite films plays an important role in tandem solar cells. Therefore, it is necessary to improve the performance of WBG perovskite films for the development of tandem solar cells. Here, we employ F-type pseudo-halogen additives (PF or BF) into perovskite precursors.

General heterostructure strategy of photothermal materials for scalable solar-heating hydrogen production without the consumption of artificial energy.

Solar-heating catalysis has the potential to realize zero artificial energy consumption, which is restricted by the low ambient solar heating temperatures of photothermal materials. Here, we propose the concept of using heterostructures of black photothermal materials (such as BiTe) and infrared insulating materials (Cu) to elevate solar heating temperatures. Consequently, the heterostructure of BiTe and Cu (BiTe/Cu) increases the 1 sun-heating temperature of BiTe from 93 °C to 317 °C by achieving the synergy of 89% solar absorption and 5% infrared radiation.

High-performance broadband position-sensitive detector based on lateral photovoltaic effect of PbSe heterostructure.

PbSe has attracted considerable attention due to its promising applications in optoelectronics and energy harvesting. In this work, we explore the lateral photovoltaic effect (LPE) of PbSe films with a simple PbSe/Si heterostructure under nonuniform light illumination and zero-bias conditions. The LPE response is strongly dependent on the thickness of the PbSe film, but always shows a linear dependence on the laser spot position in an ultra-large working size of 5 mm and exhibits a wide photoresponse ranging from visible to near-infrared.

Additive Engineering for Efficient and Stable MAPbI-Perovskite Solar Cells with an Efficiency of over 21.

The high density of defects in MAPbI perovskite films brings about severe carrier nonradiative recombination loss, which lowers the performance of MAPbI-based perovskite solar cells (PSCs). Here, methylamine cyanate (MAOCN) molecules were introduced into MAPbI solutions to manipulate the crystallizatsion of the MAPbI films. MAOCN molecules can slow down the volatilization rate of the solvent and delay the crystallization process of the MAPbI film.

High-Responsivity, Fast, and Self-Powered Narrowband Perovskite Heterojunction Photodetectors with a Tunable Response Range in the Visible and Near-Infrared Region.

In recent years, narrowband photodetectors (PDs) have been widely used in color imaging, spectral detection or discrimination, defense, and scientific research due to their special spectral selective responses. In this work, by combining organic-inorganic hybrid perovskite layers of different band gaps and thicknesses, a series of narrowband perovskite heterojunction PDs with a continuously adjustable spectral range in the visible and near-infrared range are designed and prepared. The PDs can achieve a narrowband photoresponse with a full width at half-maximum (FWHM) of less than 50 nm and a light rejection ratio (between 780 and 532 nm) of over 1100 and exhibit excellent photoresponse performances with an external quantum efficiency (EQE), responsivity (), and detectivity (*) as high as 50.

Ambient sunlight-driven photothermal methanol dehydrogenation for syngas production with 32.9 % solar-to-hydrogen conversion efficiency.

Methanol dehydrogenation is an efficient way to produce syngas with high quality. The current efficiency of sunlight-driven methanol dehydrogenation is poor, which is limited by the lack of excellent catalysts and effective methods to convert sunlight into chemicals. Here, we show that atomically substitutional Pt-doped in CeO nanosheets (Pt-CeO) exhibit excellent methanol dehydrogenation activity with 500-hr level catalytic stability, 11 times higher than that of Pt nanoparticles/CeO.

Photoluminescence characterization of wetting layer and carrier dynamics for coupled InGaAs/GaAs surface quantum dot pair structures.

The optical properties are investigated by spectroscopic characterizations for bilayer InGaAs/GaAs quantum dot (QD) structures consisting of a layer of surface quantum dots (SQDs) separated from a layer of buried quantum dots (BQDs) by different GaAs spacers with thicknesses of 7 nm, 10.5 nm and 70 nm. The coupling from the BQDs to SQDs leads to carrier transfer for the two samples with thin spacers, 7 nm and 10.

Type-II GaSb quantum dots grown on InAlAs/InP (001) by droplet epitaxy.

GaSb quantum dots (QDs) have been grown by droplet epitaxy within InAlAs barrier layers on an InP (001) substrate. The droplet growth mode facilitates a larger size (average height ∼4.5 nm) and a lower density (∼6.

Lateral bipolar photoresistance effect in the CIGS heterojunction and its application in position sensitive detector and memory device.

Cu(In,Ga)Se (CIGS) based multilayer heterojunction, as one of the best high efficiency thin film solar cells, has attracted great interest due to its outstanding features. However, the present studies are primarily focused on the structure optimization and modulation in order to enhance the photoelectric conversion efficiency. Here, we exploit another application of this multilayer heterostructure in photoresistance-modulated position sensitive detector by introducing lateral photoresistance effect.

Enhanced Light-Induced Transverse Thermoelectric Effect in Tilted BiCuSeO Film via the Ultra-thin AuNPs Layer.

Significant enhancement of light-induced transverse thermoelectric (LITT) effect in tilted BiCuSeO film has been achieved via introduction of an ultra-thin layer of gold nanoparticles (AuNPs) with the thickness of a few nanometers. In both cases of pulsed and continuous light irradiation, about two times increment in the LITT voltage sensitivity is observed for the BiCuSeO film coated with 4-nm-thick AuNPs layer. This can be ascribed to the increased photo-thermal conversion efficiency in the LITT effect owing to the efficient usage of the incident light of AuNPs layer.

Interplay Effect of Temperature and Excitation Intensity on the Photoluminescence Characteristics of InGaAs/GaAs Surface Quantum Dots.

We investigate the optical properties of InGaAs surface quantum dots (SQDs) in a composite nanostructure with a layer of similarly grown buried quantum dots (BQDs) separated by a thick GaAs spacer, but with varied areal densities of SQDs controlled by using different growth temperatures. Such SQDs behave differently from the BQDs, depending on the surface morphology. Dedicated photoluminescence (PL) measurements for the SQDs grown at 505 °C reveal that the SQD emission follows different relaxation channels while exhibiting abnormal thermal quenching.

Correlation between photoluminescence and morphology for single layer self-assembled InGaAs/GaAs quantum dots.

Single layer self-assembled InGaAs quantum dots (QDs) are manipulated by using different arsenic species on GaAs (100) surface. The As molecules are experimentally observed to be more promising than As to promote the formation of one-dimensionally-aligned QD-chain arrays. The lateral alignment of QDs and the corresponding formation of dot chains are explained by the anisotropic surface kinetics in combination with the different reactivities of the two molecules with bonding sites on the GaAs (100) surface.

Ultrahigh, Ultrafast, and Self-Powered Visible-Near-Infrared Optical Position-Sensitive Detector Based on a CVD-Prepared Vertically Standing Few-Layer MoS/Si Heterojunction.

MoS, as a typical transition metal dichalcogenide, has attracted great interest because of its distinctive electronic, optical, and catalytic properties. However, its advantages of strong light absorption and fast intralayer mobility cannot be well developed in the usual reported monolayer/few-layer structures, which make the performances of MoS-based devices undesirable. Here, large-area, high-quality, and vertically oriented few-layer MoS (V-MoS) nanosheets are prepared by chemical vapor deposition and successfully transferred onto an Si substrate to form the V-MoS/Si heterojunction.

High-Efficiency and Stable Organic Solar Cells Enabled by Dual Cathode Buffer Layers.

Various cathode interface materials have been used in organic solar cells (OSCs) to realize high performance. However, most cathode interface materials have their respective weaknesses in maximizing the efficiency or stability of OSCs. Herein, three kinds of alcohol-soluble cathode interfacial materials are combined with bathocuproine (BCP) to serve as multifunctional bilayer cathode buffers for the regular OSCs, and thus greatly enhanced power conversion efficiencies over 10.

Ultrahigh power factors in P-type 1T-ZrX (X = S, Se) single layers.

The thermoelectric performances of 1T-ZrX (X = S and Se) single layers were investigated using a combination of density functional calculations and semi-classical Boltzmann transport theory. Because of the high hole mobilities at 300 K, ultrahigh power factors (PF=Sσ) were found in the P-type compounds; these values were ∼ 11.95 and ∼13.

SbS thickness-dependent lateral photovoltaic effect and time response observed in glass/FTO/CdS/SbS/Au structure.

As an interesting one dimensional ribbon material, SbS has recently attracted much attention in recent years due to its exciting optical properties. However, SbS-based photovoltaic or photoelectronic devices are still in research, and there are many things unknown to us and need to be well studied. In this work, the glass/FTO/CdS/SbS/Au structures were successfully prepared with different SbS thicknesses, and the lateral photovoltaic effect (LPE) was firstly observed in this structure, suggesting its great potential in position sensitivity detectors (PSD).

Large Lateral Photovoltage Observed in MoS Thickness-Modulated ITO/MoS/p-Si Heterojunctions.

Molybdenum disulfide (MoS), as a typical two-dimensional (2D) material, has attracted extensive attention in recent years because of its fascinating optical and electric properties. However, the applications of MoS have been mainly in photovoltaic devices, field-effect transistors, photodetectors, and gas sensors. Here, it is demonstrated that MoS can be found another important application in position sensitive detector (PSD) based on lateral photovoltaic effect (LPE) in it.

Photoluminescence Study of the Interface Fluctuation Effect for InGaAs/InAlAs/InP Single Quantum Well with Different Thickness.

Photoluminescence (PL) is investigated as a function of the excitation intensity and temperature for lattice-matched InGaAs/InAlAs quantum well (QW) structures with well thicknesses of 7 and 15 nm, respectively. At low temperature, interface fluctuations result in the 7-nm QW PL exhibiting a blueshift of 15 meV, a narrowing of the linewidth (full width at half maximum, FWHM) from 20.3 to 10 meV, and a clear transition of the spectral profile with the laser excitation intensity increasing four orders in magnitude.

Lateral photovoltaic effect observed in doping-modulated GaAs/AlGaAs.

For photovoltaic effect (PE), both barrier height and carrier lifetime are all very important factors. However, how to distinguish their contributions to the PE is very difficult. In this paper, we prepared a series of GaAs/AlGaAs two dimensional electron gas (2DEG) with typical AlGaAs doping concentration of 0.

Variations of thermoelectric performance by electric fields in bilayer MX (M = W, Mo; X = S, Se).

A gate electrode is usually used to controllably tune the carrier concentrations, further modulating the electrical conductivity and the Seebeck coefficient to obtain the optimum thermoelectric figure of merit (ZT) in two-dimensional materials. On the other hand, it is necessary to investigate how an electric field induced by a gate voltage affects the electronic structures, further determining the thermoelectric properties. Therefore, by using density functional calculations in combination with Boltzmann theory, the thermoelectric properties of bilayer MX (M = W, Mo; X = S, Se) with or without a 1 V nm perpendicular electric field are comparatively investigated.

Thermoelectric properties of fullerene-based junctions: a first-principles study.

This study is built on density functional calculations in combination with the non-equilibrium Green's function, and we probe the thermoelectric transport mechanisms through C molecules anchored to Al nano-electrodes in three different ways, such as, the planar, pyramidal, and asymmetric surfaces. When the electrode is switched from the planar and pyramidal surfaces, the electrical conductance (σ) and electron's thermal conductance (κ) decrease almost two orders of magnitude due to the reduction of the molecule-electrode contact coupling, whereas the Seebeck coefficients (S) are reduced by ∼55%. Furthermore, the maximum electron's thermoelectric figure of merit (ZT = SσT/κ, assuming a vanishing phonon's thermal conductance) is about 0.

Enhanced thermoelectric performance of CdO : Ag nanocomposites.

CdO : Ag nanocomposites with metallic Ag nanoparticles embedded in the polycrystalline CdO matrix were synthesized by the solid-state reaction method. The addition of Ag led to increased grain boundaries of CdO and created numerous CdO/Ag interfaces. By incorporating Ag into the CdO matrix, the power factor was increased which was probably due to the carrier energy filtering effect induced by the enhanced energy-dependent scattering of electrons.

Synthesis of Na-doped ZnO hollow spheres with improved photocatalytic activity for hydrogen production.

The fabrication of p-type doped ZnO nanostructures is key in opening up substantial opportunities for the application of ZnO nanostructures. Owing to their stable p-type property, Na ions are the best candidates for ZnO p-type doping. However, Na-doped ZnO nanostructures had never been prepared until now.

Strain and electric field co-modulation of electronic properties of bilayer boronitrene.

The electronic properties of bilayer strained boronitrenes are investigated under an external electric field using density functional methods. Our result is just the same as the previous conclusion: ie, that the electric field will reduce their band gaps. Except for the decrease of their band gaps, the degeneracy of π valence bands at K points will be lifted and the degenerate gap will increase with the electric field increasing.