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The photosensitivity of silicon is inherently very low in the visible electromagnetic spectrum, and it drops rapidly beyond 800 nm in near-infrared wavelengths. Herein, we have experimentally demonstrated a technique utilizing photon-trapping surface structures to show a prodigious improvement of photoabsorption in one-micrometer-thin silicon, surpassing the inherent absorption efficiency of gallium arsenide for a broad spectrum. The photon-trapping structures allow the bending of normally incident light by almost ninety degrees to transform into laterally propagating modes along the silicon plane. Consequently, the propagation length of light increases, contributing to more than an order of magnitude improvement in absorption efficiency in photodetectors. This high absorption phenomenon is explained by FDTD analysis, where we show an enhanced photon density of states while substantially reducing the optical group velocity of light compared to silicon without photon-trapping structures, leading to significantly enhanced light-matter interactions. Our simulations also predict an enhanced absorption efficiency of photodetectors designed using 30 and 100-nanometer silicon thin films that are compatible with CMOS electronics. Despite a very thin absorption layer, such photon-trapping structures can enable high-efficiency and high-speed photodetectors needed in ultra-fast computer networks, data communication, and imaging systems with the potential to revolutionize on-chip logic and optoelectronic integration., Comment: 24 pages, 4 figures

The study of defect centers in silicon has been recently reinvigorated by their potential applications in optical quantum information processing. A number of silicon defect centers emit single photons in the telecommunication $O$-band, making them promising building blocks for quantum networks between computing nodes. The two-carbon G-center, self-interstitial W-center, and spin-$1/2$ T-center are the most intensively studied silicon defect centers, yet despite this, there is no consensus on the precise configurations of defect atoms in these centers, and their electronic structures remain ambiguous. Here we employ \textit{ab initio} density functional theory to characterize these defect centers, providing insight into the relaxed structures, bandstructures, and photoluminescence spectra, which are compared to experimental results. Motivation is provided for how these properties are intimately related to the localization of electronic states in the defect centers. In particular, we present the calculation of the zero-field splitting for the excited triplet state of the G-center defect as the structure is transformed from the A-configuration to the B-configuration, showing a sudden increase in the magnitude of the $D_{zz}$ component of the zero-field splitting tensor. By performing projections onto the local orbital states of the defect, we analyze this transition in terms of the symmetry and bonding character of the G-center defect which sheds light on its potential application as a spin-photon interface., Comment: 11 pages, 6 figures

Silicon photodiode-based CMOS sensors with backside-illumination for 300–1100 nm wavelength range were studied. We showed that a single hole in the photodiode increases the optical efficiency of the pixel. In near-infrared wavelengths, the enhancement allows 70% absorption in a $3~\mu \text{m}$ thick Si. It is $4\times $ better than that for the flat pixel. We compared different shapes and sizes of single hole and hole arrays. We have shown that a certain size and shape in single hole-based pixels contribute to stronger enhancement of optical efficiencies. The crosstalk was successfully reduced by employing trenches between pixels. We optimized the dimensions of the trenches to achieve minimal pixel separation for $1.12~\mu \text{m}$ pixels.

The growth of high-quality nanostructures using chemical vapor deposition (CVD) normally requires metal catalysts, which when incorporated in the nanostructures may severely affect their properties. Here, we report on the non-catalytic CVD growth of all-inorganic CsPbX3 (X = Br, Cl) perovskite nanowires (NWs) with an emphasis on understanding the growth mechanism via detailed electron microscopy and spectroscopic studies at different stages of the growth. We show that the chemical vapors initiate the nucleation and growth of halide nanoparticles, followed by structural transformations through axial elongation into nano-capsules and dumbbells, and eventually these dumbbells meet and form complete NWs. This growth mechanism is independent of the substrate crystallinity and detailed spectroscopic measurements demonstrate that nanoscale features at different growth stages have similar material properties as the final NWs. We believe that this self-assembly mechanism can be extended to understand the evolution of nanostructures in other semiconductor materials and to tune their characteristics to enhance their functionalities for novel optoelectronic devices.

All-inorganic halide perovskites (IHP), CsPbX3 (X = Cl, Br, I) exhibiting efficient optical emissions within the spectral range of 410 to 730 nm are potential candidates for many optoelectronic devices. Anion alloying of these IHPs is expected to achieve tunable emission wavelength covering the entire visible spectrum. Here, we developed a two-step chemical vapor deposition (CVD) process for growing quaternary IHP CsPbX3 (X = Cl/Br and Br/I) alloys. By exploiting the fast diffusion of halide anions in IHPs, the alloy composition can be precisely controlled by the growth time of the respective layers once the growth of the individual ternary IHP is optimized. Hence complexities in the multi-parameter optimization in the conventional CVD growth of quaternary alloys can be mitigated. Using this process, we synthesized single crystalline, homogeneous and thermally stable CsPbCl3(1−X)Br3x and CsPbBr3(1−X)I3x perovskites alloy microplates and demonstrated continuously tunable emission covering the spectrum from 428 to 715 nm by varying the halide compositions in the alloys. These alloy microplates also exhibit room temperature amplified spontaneous emissions (ASE) along with strong photonic discharges from the microplate’s edges and hence are potentially useful as a gain medium as well as optical cavities for emissions with wavelengths covering the visible spectrum.

Perovskite/silicon tandem solar cells are considered as one of the cost-effective solutions for determining high energy conversion efficiencies. Efficient photon management allows improving light incoupling in solar cells by reducing optical losses. The optics relies upon the interface morphology, and consequently, the growth mechanism of the top cell on the bottom cell is crucial for the implementation of efficient perovskite/silicon tandem solar cells. To describe the interface morphologies of perovskite/silicon tandem solar cells, a three-dimensional surface algorithm is used that allows investigating the perovskite solar cells deposited on the textured crystalline silicon solar cells. We distinguish between two extreme cases in which the film grows only in the direction of the substrate normal or in the direction of the local surface normal. The growth mode has significant influence on the film roughness, the effective thickness of the film, the optics of the solar cell, and the photovoltaic parameters. The optics is investigated by finite-differencetime-domain simulations. The influence of the interface morphology on the photovoltaic parameters is discussed, and guidelines are provided to reach high short-circuit current density and energy conversion efficiency.

The short-circuit current density and energy conversion efficiency of single-junction perovskite and perovskite/perovskite tandem solar cells can be increased by photon management. In this study, optical metasurfaces were investigated as potential light trapping structures oppose to commonly used pyramidal surface textures. Herein, metal oxide-based non-resonant metasurfaces were investigated as potential light-trapping structures in perovskite solar cells. The zinc oxide nanowire-based building blocks of the metasurface can be prepared by a templated electrodeposition through a mask of resist. The phase of the incident light can be controlled by the edge length of the subwavelength large zinc oxide nanowires. An array of zinc oxide nanowires was prepared and characterized in the current study. Three-dimensional (3D) finite-difference time-domain (FDTD) optical simulations were used to compare solar cells covered with non-resonant metasurfaces with commonly used light trapping structures. As compared to the solar cells covered with zinc oxide pyramid surface texture, solar cells with the integrated non-resonant metasurfaces exhibit almost identical quantum efficiencies and short-circuit current densities. Investigations of such metasurfaces will not only improve the photon absorption in perovskite solar cells but also reveal a pathway to make high-efficiency next-generation solar cells. Detailed guidelines for the realization of non-resonant metal oxide metasurfaces will be provided.

Quantum light sources play a fundamental role in quantum technologies ranging from quantum networking to quantum sensing and computation. The development of these technologies requires scalable platforms, and the recent discovery of quantum light sources in silicon represents an exciting and promising prospect for scalability. The usual process for creating color centers in silicon involves carbon implantation into silicon, followed by rapid thermal annealing. However, the dependence of critical optical properties, such as the inhomogeneous broadening, the density, and the signal-to-background ratio, on centers implantation steps is poorly understood. We investigate the role of rapid thermal annealing on the dynamic of the formation of single color centers in silicon. We find that the density and the inhomogeneous broadening greatly depend on the annealing time. We attribute the observations to nanoscale thermal processes occurring around single centers and leading to local strain fluctuations. Our experimental observation is supported by theoretical modeling based on first principles calculations. The results indicate that annealing is currently the main step limiting the scalable manufacturing of color centers in silicon.

Single-aperture cavities are a key component of lasers that are instrumental for the amplification and emission of a single light mode. However, the appearance of high-order transverse modes as the size of the cavities increases has frustrated efforts to scale-up cavities while preserving single-mode operation since the invention of the laser six decades ago

In this study, optical multispectral sensors based on perovskite semiconductors have been proposed, simulated, and characterized. The perovskite material system combined with the 3D vertical integration of the sensor channels allow for realizing sensors with high sensitivities and a high spectral resolution. The sensors can be applied in several emerging areas, including biomedical imaging, surveillance, complex motion planning of autonomous robots or vehicles, artificial intelligence, and agricultural applications. The sensor elements can be vertically integrated on a readout electronic to realize sensor arrays and multispectral digital cameras. In this study, three- and six-channel vertically stacked perovskite sensors are optically designed, electromagnetically simulated, and colorimetrically characterized to evaluate the color reproduction. The proposed sensors allow for the implementation of snapshot cameras with high sensitivity. The proposed sensor is compared to other sensor technologies in terms of sensitivity and selectivity.

Platinum disulfide (PtS2), a member of the recently developed group 10 transition metal dichalcogenide (TMD) materials, exhibits great potential in optoelectronics applications. Nevertheless, its photoluminescence (PL) behavior still remains obscure. Quantum dots (QDs) are believed having the capability to enhance photoluminescence property compared to the bulky or layered structure owing to their quantum confinement effects. Inspired by remarkable PL enhancement works on other TMD materials QDs, the fabrication of PtS2 QDs suspension via a low-cost liquid exfoliation technique is demonstrated in this work. The PtS2 QDs with an average diameter of 3.9 nm and average thickness of 2.9 nm are observed, respectively. For the first time, the PL spectra of PtS2 QDs suspension are successfully obtained and monitored over time. The PL spectra display an excitation-dependent luminescence. The maximum emission peak is observed at 407.2 nm for the excitation wavelength of 330 nm. This PtS2 QDs also shows a decent long-term stability. These results open up encouraging prospects of luminescence applications of PtS2 QDs.

Utilizing solar energy to evaporate water is a green and promising approach in addressing the issue of global freshwater shortage and water pollution. Carbon materials have gained extensive research attention as efficient solar absorbers for solar steam generation owing to the non-toxic nature and environmental friendliness. In this work, the metal-organic framework (MOF) derived porous carbon (MDPC) materials were first employed as solar absorbers for enhancing water evaporation. An efficient surface heating and evaporation system was designed by coating the leaf-like two-dimensional (2D) MOF precursor on stainless steel mesh followed by calcination (MDPC/SS mesh), and then in conjunction with a floating air-laid paper wrapped polyethylene (EPE) foam. The prepared solar evaporator with unique light trapping structures shows a high solar absorption (>97%), excellent hydrophilicity, and great surface heat localization for solar steam generation. Consequently, a photo-thermal conversion efficiency of 84.3% with an evaporation rate of 1.222 kg m−2 h−1 was achieved under one sun illumination. Furthermore, the MDPC/SS mesh shows good recyclability and durability. This work opens a new avenue for the application of MOF derived carbon as photo-thermal material in the field of solar steam generation.

The front contact has a major impact on the electrical and optical properties of perovskite solar cells. The front contact is part of the junction of the solar cell and must provide lateral charge transport to the terminals and should allow for an efficient light incoupling, while having low optical losses. The complex requirements of the perovskite solar front contact will be described and the optics of the front contact will be investigated. It will be shown that the front contact has a distinct influence on the short-circuit current and energy conversion efficiency. Metal oxide films were investigated as potential front contacts. The incoupling of light in the solar cell is investigated by three-dimensional finite-difference time-domain optical simulations and optical measurements of experimentally realized self-textured zinc oxide films. The zinc oxide films were prepared by metal-organic chemical vapor deposition at low temperatures. Furthermore, the influence of free carrier absorption of metal oxide films on the optics of low bandgap and/or tandem solar cells is investigated. Guidelines are provided on how to choose the doping concentration and thickness of the metal oxide films. Finally, it will be shown that by selecting an optimal front contact design the short-circuit current and energy conversion efficiency can be increased by at least 15%.

The short circuit current of perovskite/silicon tandem solar cells has to be increased to realize solar cells with energy conversion efficiencies exceeding the records of single junction solar cells. Photon management allows for increasing the short-circuit current and energy conversion efficiency of perovskite single junction and perovskite/silicon tandem solar cells due to improved light incoupling and/or light trapping. In this study, an electrically flat but optically rough solar cell design is investigated, which combines the benefit of reaching high short-circuit currents, while maintaining the integrity of perovskite films processed on planar substrates or surfaces. Consequently, the perovskite films exhibit electrical properties comparable to planar perovskite solar cells , which allows for achieving solar cells with high open circuit voltage and fill factors. Electrically flat but optically rough perovskite solar cell structures can be successfully implemented because the perovskite material system and the contact materials of the solar cells exhibit comparable refractive indices . This sets the perovskite material system with its low refractive index apart from other high refractive index materials like silicon or germanium . Hence the proposed design of an electrically flat but optically rough solar cell cannot be applied to silicon or germanium solar cells. The design of perovskite single junction solar cells is discussed, and electrically flat but optically rough solar cells are compared to electrically and optically rough solar cells. The design of perovskite/silicon tandem solar cells is investigated by using a hybrid approach, which combines Finite Difference Time Domain optical simulations of perovskite top and experimentally measured crystalline bottom solar cells. Detailed guidelines are provided on how to achieve high short-circuit currents.

Platinum disulfide (PtS2) has recently drawn extensive research interest due to its excellent electronic properties, controllable bandgap over a broad range, and high air stability. Herein, we demonstrate the generation of mode-locked ultrafast laser pulses by using PtS2 nanosheets for the first time, which were fabricated by ultrasonic exfoliation followed by the centrifugation process. The fabricated PtS2 saturable absorber (SA) was used within two different fiber laser systems. Ultrafast laser pulses with pulse duration of 2.1 ps, 3-db bandwidth of 2.5 nm, and repetition rate of 15.04 MHz were produced from an Er-doped fiber laser system with an operational wavelength of 1.572 μm. Additionally, a mode-locking pulse train with repetition rate of 11.2 MHz was obtained by using the fabricated PtS2 SA within Yb-doped fiber laser system with operational wavelength of ∼1 μm. It is expected that these results will trigger further research with wide potential applications of PtS2 in the field of nonlinear optics and ultrafast photonics.

Silicon photodetectors (PDs) operating at near‐IR wavelengths with high speed and high sensitivity are becoming critical for emerging applications, such as light detection and ranging (LIDAR) systems, quantum communications, and medical imaging. However, such PDs present a bandwidth‐absorption trade‐off at those wavelengths that have limited their implementation. Photon‐trapping (PT) structures address this trade‐off by enhancing the light–matter interactions, but maximizing their performance remains a challenge due to a multitude of factors influencing their design and fabrication. Herein, strategies to improve the PT effect while enhancing the speed of operation are investigated. By optimizing the design of PT structures and experimentally integrating them in high‐speed PDs, a simultaneous broadband absorption efficiency enhancement up to 1000% and a capacitance reduction of more than 50% are achieved. Empirical equations correlate the quantum efficiency of PDs with the physical properties of the PT structures, material characteristics, and limitations of the fabrication technologies. The results that are obtained open routes toward designing cost‐effective complementary metal–oxide‐semiconductor (CMOS)‐integrated receivers.

Improving the time resolution and sensitivity of Silicon-based Single Photon Avalanche Photodetectors (Si-SPAD) across the entire visible spectrum is critical to improve image quality in biomedical imaging applications such as positron emission tomography or fluorescence lifetime imaging. This work reports on the feasibility of manipulating the penetration depth of photons with 450 nm wavelengths to enhance absorption in Si-SPAD by means of photon trapping structures. Optical-electrical simulations suggest light can be directed towards critical regions of the semiconductor increasing the absorption from 54 to 90% with only 1.2μm of silicon and enhancing the probability of avalanche by electrons that leads to higher multiplication gain and speed of operation.

Photon management of perovskite solar cells (PSCs) is studied by the use of nanohole front contact, which allows improving the JSC of the PSC by providing an improved light incoupling. The front contact integrated with spherical nanocone shaped holes represent a refractive index grating allowing for light incoupling approaching unity while minimizing reflection losses. Besides, the front contact has a comparable refractive index (n~2.5) with the perovskite absorber, which minimizes the front reflections in PSC. Optics and optimization of front contact and solar cell are investigated by three-dimensional (3D) finite-difference time-domain (FDTD) simulations whereas finite element method simulations are used to study the electrical response of the device. Investigations reveal a maximum light incoupling enhancement of 10~12% for the optimized PSC, leading to 10 to 27% JSC enhancement with respect to the planar reference PSC.

Highlights Industrially viable bottom-up spray pyrolysis deposition technique was used to prepare the highly compact TiO2 film, which is a vital element for the multi-layer front contact.The optimization of the front contact is presented by fabricating reproducible and efficient perovskite solar cellsMulti-layer front contact is applied to realize efficient perovskite single-junction and perovskite/perovskite tandem solar cells, where optics and electrical effects of solar cells are studied by optically coupled 3D electromagnetic simulations. Electronic supplementary material The online version of this article (10.1007/s40820-020-00559-2) contains supplementary material, which is available to authorised users., The photovoltaic performance of perovskite solar cells (PSCs) can be improved by utilizing efficient front contact. However, it has always been a significant challenge for fabricating high-quality, scalable, controllable, and cost-effective front contact. This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells (TSCs). As a critical part of the front contact, we prepared a highly compact titanium oxide (TiO2) film by industrially viable Spray Pyrolysis Deposition (SPD), which acts as a potential electron transport layer (ETL) for the fabrication of PSCs. Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs. As the front contact has a significant influence on the optoelectronic properties of PSCs, hence, we investigated the optics and electrical effects of PSCs by three-dimensional (3D) finite-difference time-domain (FDTD) and finite element method (FEM) rigorous simulations. The investigation allows us to compare experimental results with the outcome from simulations. Furthermore, an optimized single-junction PSC is designed to enhance the energy conversion efficiency (ECE) by > 30% compared to the planar reference PSC. Finally, the study has been progressed to the realization of all-perovskite TSC that can reach the ECE, exceeding 30%. Detailed guidance for the completion of high-performance PSCs is provided. Electronic supplementary material The online version of this article (10.1007/s40820-020-00559-2) contains supplementary material, which is available to authorised users.

In this study, a high-quality TiO 2 compact layer (CL) is prepared by Spray Pyrolysis Deposition (SPD), which is employed as a potential ETL for the realization of PSCs. To optimize the ETL, the thickness of the TiO 2 -CL is varied from 20 nm to 200 nm with a step size of 20 nm, where the photovoltaic performance of each is systematically computed. The optics of the solar cell is investigated by 3D finite-difference time-domain simulations, where electrical parameters are analyzed through finite element method simulations. The optimized thickness of the TiO 2 -CL ETL exhibits a maximum energy conversion efficiency of 19.46%. Detailed guidelines for the optimization process and device design are provided.

Group-10 transition metal dichalcogenide (TMD) materials have recently attracted considerable attention in optoelectronics applications. However, so far their quantum dot (QD) counterparts with photoluminescence (PL) nature still remain to be revealed. In this study, 2 typical types of group-10 TMD material (PdS2 and PdSe2) QDs are fabricated via liquid exfoliation using N-methyl-2-pyrrolidone (NMP) solvent. The absorption and PL spectra of these QD solutions are studied, exhibiting excitation wavelength-dependent behaviors and large Stokes shifts. Furthermore, the quantum yield and decay lifetime are also investigated and analyzed. The obtained results suggest promising optoelectronic applications with group-10 TMD QDs in the future.

Solar cells based on semiconductor materials with low diffusion lengths like organics and amorphous silicon exhibit short circuit currents and energy conversion efficiencies distinctly below the detailed balance limit (commonly called the Shockley Queisser limit). The short circuit current and energy conversion efficiency of such solar cells can be increased by employing a 3D device architecture. The 3D device architecture leads to a distinct gain in the optical thickness of such solar cells compared to a conventional planar solar cell, while the electrical thickness of the investigated 3D and planar solar cells is equal. Hence a short circuit current can be achieved close to the theoretical upper limit. In this study, a 3D organic solar cell is studied. The influence of the 3D architecture on the solar cell performance parameters of a small molecule organic solar cell was investigated. Finite-difference time-domain optical simulations are utilized to determine the quantum efficiency and short circuit current of the 3D solar cell structure. A guideline is provided on how to achieve a high energy conversion efficiency with a 3D solar cell. The proposed approach is not only applicable to organic solar cells. The approach is applicable to all solar energy materials with low diffusion length and/or low charge carrier mobility.

Image sensing technology has a great impact on our daily life as well as the entire society, such as health, safety and security, communication systems, and entertainment. The conventional optical color sensors consist of side by side arranged optical filters for three basic colors (blue, green, and red). Hence, the efficiency of such optical color sensors is limited by only 33%. In this study, a vertically stacked color sensor is investigated with perovskite alloys, which has the potential to provide the efficiency approaching 100%. The proposed optical sensor will not be limited by color Moire error or color aliasing. Perovskite materials with suitable bandgaps are determined by applying the energy shifting model and the optical constants are used for further investigations. Quantum efficiencies and spectral responsivities of the described color sensors are investigated by three-dimensional electromagnetic simulations. Investigated spectral sensitivities are further analyzed for the

Color imaging experiment demonstrates a photochromic behavior of mixed-halide perovskites upon dark and light excitation, while the color emitted by the crystals changes from red to yellow and vice versa with the intensity of excitation light source. Unlike the photochromic property commonly observed in solution-state polymer materials, solid-state perovskite materials with photochromic behavior might open wide applications in consumer products and electronic devices. In the next part, we report on a reversible photoluminescence (PL) peak in iodide-based organic-inorganic lead halide perovskite materials under a 2-photon absorption process, while tuning the excitation wavelength. Intriguingly, two shorter wavelength peaks are visible and become prominent when the excitation photon energy is being tuned in the high energy spectrum, while laser power is remained constant. The same phenomenon of reversible PL peak is also observed in various iodine-based organic-inorganic halides as well as all-inorganic perovskite single crystals and polycrystals. We attribute to the reversible PL peak phenomenon to the photoinduced structural deformation and the associated change in the optical bandgap of iodide perovskites under the femtosecond laser excitation. Our findings will introduce a degree of freedom in future research as well as adding functionalities to optoelectronic applications in these emerging perovskite materials-based devices.

We present a strategy for photon management in front contact of perovskite solar cells (PSCs) compatible with tandem and flexible PSCs capable of optimizing device characteristics while providing an additional mechanism to overcome excessive focusing that affects the device’s photostability. Rigorous validation of the numerical modeling used was performed by fabricating PSCs in a superstrate configuration optimized to reach high performance, ECE = 17.4%, VOC = 1.02 V, JSC = 22.3 mA/cm2, and FF = 77%. These 3D electromagnetic simulations combining the finite-difference time-domain (FDTD) and finite element method (FEM) techniques provide detailed insights of the photonic and electrical effects in PSCs. Numerical optimization of the dual capabilities of a novel nanostructured front contact enables control of the absorbed power density distribution to maximize efficiency while simultaneously minimizing nanostructure-related sub-wavelength focusing effects. In-depth analysis of the proposed photon management reveals enhanced electrical characteristics to maximize charge extraction leading to JSC enhancements of ~15 that can be as high as 33% for ultra-thin active layers suitable for flexible PSCs compared to planar PSCs performance. Furthermore, we show that the design of the front contact layer’s nanostructure enables control of the power density distribution in the device to engineer PSCs' photostability without compromising performance enhancements afforded by the nanophotonic front contact. Details of the nanophotonic front contact, device, and fabrication process are provided.

The perovskite material system allows for the realization of perovskite/silicon tandem solar cells with high energy conversion efficiencies at low cost. To realize such solar cells, the device geometry, the device processing, and the contact materials have to be modified in comparison to single junction perovskite solar cells. In this study, perovskite/silicon tandem solar cells are designed allowing for the generation of short-circuit current densities and energy conversion efficiencies exceeding 20 mA cm−2 and 30%, while using realistic device structures. High short-circuit current densities can be achieved by minimizing reflection losses and optical losses of the contact layers. A hybrid approach is used to investigate the optics by combining finite-difference time-domain simulations with experimental measurements. Details on the nanophotonic design will be provided and discussed.

The abundant waste polyurethane sponge, commonly considered as one of the municipal wastes, can be recycled and converted into the valuable resources of environment. The increasing landfill cost and air-pollutions have made it a great urgent to develop the effective applications of waste polyurethane sponge. Recently, solar vapor generation has attracted extensive attentions, since energy shortage and water scarcity along with water pollution are becoming alarming global issues to be addressed. The solar vapor generation relies on the performance of the solar absorbers which convert the solar energy into heat for the vaporization process. A low cost, efficient and durable solar absorber is vital for the development of solar vapor generation. Here, we report that the recycled self-floating black polyurethane sponges are very promising solar absorber materials. which can efficiently generate water vapor after a simple one-step hydrophilic treatment with dopamine hydrochloride. The evaporating rate was more than 3.5 times higher compared to that of the existing natural evaporation process, exhibiting an evaporation efficiency of above 50%. Furthermore, this black polyurethane sponge can also drive solar ethanol distillation, yielding up to 25 wt% concentration promotion under each distillation cycle.

In thin-film solar cells, the photocurrent conversion productivity can be distinctly boosted-up utilizing a proper back reflector. Herein, the impact of different smooth and textured back reflectors was explored and effectuated to study the optical phenomena with interface engineering strategies and characteristics of transparent contacts. A unique type of wet-chemically textured glass-substrate 3D etching mask used in superstrate (p–i–n) amorphous silicon-based solar cell along with legitimated back reflector permits joining the standard light-trapping methodologies, which are utilized to upgrade the energy conversion efficiency (ECE). To investigate the optical and electrical properties of solar cell structure, the optical simulations in three-dimensional measurements (3D) were performed utilizing finite-difference time-domain (FDTD) technique. This design methodology allows to determine the power losses, quantum efficiencies, and short-circuit current densities of various layers in such solar cell. The short-circuit current densities for different reflectors were varied from 11.50 to 13.27 and 13.81 to 16.36 mA/cm2 for the smooth and pyramidal textured solar cells, individually. Contrasted with the comparable flat reference cell, the short-circuit current density of textured solar cell was increased by around 24%, and most extreme outer quantum efficiencies rose from 79 to 86.5%. The photon absorption was fundamentally improved in the spectral region from 600 to 800 nm with no decrease of photocurrent shorter than 600-nm wavelength. Therefore, these optimized designs will help to build the effective plans next-generation amorphous silicon-based solar cells.

Aluminum-doped and undoped zinc oxide films were investigated as potential front and rear contacts of perovskite single and perovskite/silicon tandem solar cells. The films were prepared by atomic layer deposition (ALD) at low (

Optical color sensors based on perovskites are described. These sensors overcome the limits of conventional image sensors used in smartphones and digital cameras. The sensors allow for detecting the primary colors red, green, and blue without using optical filters. The color sensors consist of vertically stacked diodes using perovskite alloys. The described sensor structure is color aliasing or color moiré error free, while conventional sensors using optical filters are limited by this error. The spectral sensitivity of vertically stacked sensors is up to three times higher than the spectral sensitivity of filter-based color sensors. The optical constants of the required perovskite alloys are determined, and color sensors are electromagnetically modeled. The spectral sensitivities of the sensors are colorimetrically characterized and compared to sensors in the literature including conventional sensors using optical filters. This study, for the first time, shows that a vertically stacked three color sensor exhibits a color error equal to, or smaller than, errors of conventional sensors using optical filters. Details on the used materials, the device design, and the colorimetric analysis are provided.

The tunable bandgap properties of perovskite materials allow attaining highly efficient tandem solar cells. An optimum bandgap for tandem solar cells can be reached by tuning the composition of halide elements in the perovskite material systems. However, realizing efficient tandem solar cells is complex, which needs a considerable understanding of device geometry and associated materials as compared to the single-junction solar cells. In this study, planar perovskite/perovskite and perovskite/silicon tandem solar cells are designed by considering realistic interface morphologies and device geometries, which can exhibit energy conversion efficiencies ~30%. Herein, the optics and optimization of solar cells are investigated by finite-difference time-domain (FDTD) simulations in three dimensions. Contact materials used in the nanophotonic design of tandem solar cells were prepared by the atomic layer deposition (ALD) of zinc oxide films. Investigated solar cells are compared in terms of their quantum efficiencies, short-circuit current densities and calculated power densities. A detailed discussion on nanophotonic device designs is provided.

Color image sensing by a smartphone or digital camera employs sensor elements with an array of color filters for capturing basic blue, green, and red color information. However, the normalized optical efficiency of such color filter-based sensor elements is limited to only one-third. Optical detectors based on perovskites are described, which can overcome this limitation. An efficient color sensor design has been proposed in this study that uses a vertically stacked arrangement of perovskite diodes. As compared to the conventional color filter-based sensors, the proposed sensor structure can potentially reach normalized optical efficiency approaching 100%. In addition, the proposed sensor design does not exhibit color aliasing or color Moire effects, which is one of the main limitations for the filter-based sensors. Furthermore, up to our knowledge, for the first time, it could be theoretically shown that both vertically arranged sensor and conventional color filter-based sensor provide almost comparable color errors. The optical properties of the perovskite materials are determined by optical measurements in combination with an energy shift model. The optics of the stacked perovskite sensors is investigated by threedimensional finite-difference timedomain simulations. Finally, colorimetric characterization was carried out to determine the color error of the sensors.