Solar Absorber Layer Research Articles

Nickel-doped silver nanoclusters as a mechanism to capture photons

Narrow width of optical absorption of conducting polymers and photons energy losses have been the challenges for fabricating highly efficient thin-film organic solar cell. Nickel-doped silver nanoclusters (Ni/Ag NCs) are employed here to capture more photons using polymers blend solar absorber medium to improve solar cell performances. The poly-3-hexylthiophene and (6-6)phenyl-C61-butyric acid methyl ester molecules blend were used a solar absorber layer in this investigation. The solar cells fabricated with NCs exhibited enhanced opt-electronic properties compared to the reference solar cell. Consequently, the experimental results suggest that the power conversion efficiency (PCE) has substantially increased with the incorporations of NCs in absorber layer, which is dependent on the concentrations of NCs in the medium. The maximum PCE achieved, in this work, is η\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta $$\\end{document} = 6.2% at 2% of NCs by weight, which has exhibited to the lowest energy losses compared to other doping levels. This improvement in PCE is attributed to the occurrence of local surface plasmon resonance effect due to the inclusion of Ni/Ag NCs in polymer matrix. The results provide valuable insights on the use of Ni/Ag NCs for efficient photons capture in thin-film polymers blend medium.

Toward improving the performance of Cu2ZnSnS4-based solar cells with Zr, W or sulfurized layers at the SnO2:F/Cu2ZnSnS4 rear interface

The photovoltaic performance of Cu2ZnSnS4 (CZTS)-based thin film solar cells with transparent back contacts is mainly constrained by the ohmic loss due to degradation of the back contacts at high temperatures required for the growth of the CZTS absorbers. This work has attempted to use ultrathin Zr and W interlayers at the SnO2:F (FTO)/CZTS interface with the purpose of improving the ohmic properties of FTO and hence the performance of solar cells. 20 nm thick Zr and W layers were coated on FTO using direct current magnetron sputtering, followed by heating at 550 °C in a sulfur atmosphere for some of the samples. Inclusion of Zr and W interlayers compromised the transmittance of the FTO back contact, however heating of the samples in a sulfur atmosphere improved the transmittance to values comparable to or better than those of un-heated FTO. Furthermore, heated W/FTO showed a significant improvement in electrical conductivity as observed from Hall effect measurements. To make complete solar cells, CZTS absorber, buffer (CdS) and window (i-ZnO/ZnO:Al) layers were sequentially deposited on the un-heated FTO, Zr/FTO, W/FTO and Mo back contacts. Glow discharge optical emmision spectroscopy confirmed that Zr and W did not diffuse into the absorber and also prevented Na diffusion into the absorber. From the scanning electron microscopy cross sectional analysis, an impovement in the absober grain size and a clear junction between the absorber and FTO with W interlayer were observed. Grazing incident X-ray diffractometry confirmed the polycrystalline nature of the CZTS thin films and indicated the presence of other phases, particularly SnS2. On the resulting solar cell parameters, the inclusion of a W interlayer reduced the series resistance from 4.5 Ωcm to 3.7 Ωcm2. An improvement in short circuit current density (JSC) is also observed, enhancing the efficiency of the solar cells with CZTS/W/FTO to 3.1 % compared to that with CZTS/Mo at 2.7 % and CZTS/FTO at 3.0 %. W was found to improve the external quantum efficiency response and JSC of the solar cells for both backside and frontside light illumination. On the other hand, inclusion of a Zr interlayer (Zr/FTO) only slighlty improved the open circuit voltage, but compromised the JSC compared to FTO and W/FTO back contacts. Thus, the findings of this study demonstrate the prospect for improving the performance of the CZTS-based thin film solar cells through the inclusion of ultrathin Zr and W interlayers between the FTO back contact and CZTS absorber.

Modeling and optimization of numerical studies on CuSbS2 thin film solar cell with ∼ 15% efficiency

In this paper, the Silvaco TCAD simulation tool is utilized for modeling of ternary chalcostibite copper antimony sulfide (CuSbS2) thin film solar cells (TFSCs). The earth-abundant CuSbS2 is a promising material as a solar absorber and hole transport layer due to its high optical absorption coefficient, and low cost. CuSbS2 based solar cell can be fabricated in vacuum-free environment. Mostly CdS is used as electron transport layer (ETL) in CuSbS2 based solar cell but the efficiency is low due to creation of Schottky barrier at the back-contact and substantial carrier recombination at the CuSbS2/CdS interface. Hence, a (ITO/n-TiO2/p-CuSbS2/Au) np heterojunction-based solar cell has been developed. The observed maximum power conversion efficiency (PCE) of 15.26% (open circuit voltage (Voc) = 823 mV, short circuit current (Jsc) = 28.48 mA/cm2, fill factor (FF) = 65.1%) is achieved by optimizing the absorber thickness (400 nm) of the solar cell. Different parameters like effect of absorber thickness, back contact, bandgap, carrier concentration, temperature, and defect density are optimized to find the best possible efficiency of the solar cell. The device also exhibits good performance stability at high temperatures. Based on results, a (ITO/n-TiO2/p-CuSbS2/Au) np heterojunction-based fabricated solar cell device is possible in future.

Improvement in spectral range of Sb 2 Se 3 absorption layer on Bi addition

Antimony selenide (Sb 2 Se 3) is a versatile material used in solar cells. The alteration in the physical properties of Sb 2 Se 3 alloys on Bi addition has been analysed. (Sb 2 Se 3)100-x Bi x (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0, and 1.2) system has been studied to examine the structural alterations by computing physical parameters. The increase in parameters, i.e., average coordination number 〈Z〉, total number of constraints per atoms (N c ), and crosslinking density (D cl ) reflect an increase in rigidity of the Sb 2 Se 3 on Bi incorporation. The computed band gap decreases on Bi addition, from 1.095 eV to 1.079 eV, indicating an approximate increase in absorption wavelength from 1132.42 nm to 1149.21 nm. An increase in rigidity reflects reduction in defect states decreasing the recombination rate within absorption layer. There are variations in cohesive energy, electronegativity, and average single-bond energy. The study reveals that this composition can be utilized to develop novel solar absorber layer materials.

Characterization of high-temperature figure of merit for solar-thermal absorbers

The figure of merit (FOM) is a widely used metric to characterize the solar-thermal conversion performance of solar absorber layers. Many of previous works have reported FOMs estimated from the radiative properties measured at room temperature. However, advanced concentrated solar power (CSP) plants operate at very high temperatures (∼750°C), which can strongly affect the absorber’s radiative properties. The present work proposes using a 1-D conduction-based reference bar technique to directly measure the converted thermal energy to determine the FOM at high absorber temperatures (≳750°C) while operating under a large solar concentration (∼1200× suns). Using the finite difference method, we carefully analyze several key parameters influencing the design of the experimental setup, such as temperature distribution, material properties, heat loss, and sensor accuracy. In addition, a rigorous uncertainty analysis is incorporated into the FOM to ascertain the confidence level of the result. We validate this new technique on a custom-built tungsten reference bar with an oxidized Inconel 625 solar-thermal absorber. A good agreement between the model and the experiment shows the reliability of the FOM measurement with a well-defined uncertainty. The same method can be implemented to measure the high-temperature FOM of most surface or volumetric solar absorbers for CSP.

Suppressing charge recombination in disordered polymers blend medium

Charge recombination is one of the critical factors that influences the performance of thin film polymer solar cells (TFPSCs). In this investigation, metal, plasmonic nano-particles are employed to suppress charge recombination and energy loss in TFPSC. Trimetallic nano-composite (NC) was successfully synthesized and composed of copper, nickel, and silver (Cu/Ni/Ag) using wet chemistry. The NC was incorporated into polymer-based solar absorber layers at different concentrations. The absorber layer is a fullerene-based bulk-heterojunction design using poly-3-hexylthiophene (P3HT) donor polymer. The results show that the power conversion efficiency of the device doped with NC has improved by 85% compared to the undoped one. The incorporation of tri-metallic NC into the polymer blend solar absorber resulted in enhanced optical absorption and improved collection of photo-current as reflected by the recorded high short circuit current density (J ) and fill factor. The enhancement of the performance is due to the occurrence of local surface plasmon resonances in the polymer medium. The experiment indicated that there is some increment in an open circuit voltage, which is attributed to the low energy losses as a result of improved exciton dissociation, charge carrier transport, and collection.

New spectrally selective coatings for CSP linear receivers operating in air at high temperature

AbstractAn attractive candidate to reduce dependence on fossil fuels and replace them by renewable sources is represented by concentrated solar power (CSP) technology, whose wide deployment is still hindered by its high investment costs. In CSP linear collector plants, a key component with high technological content may be identified in receiver tubes, that are traversed by heat transfer fluid and located on focal line on which solar radiation is concentrated by mirrors. The proposed work aims at developing spectrally selective coatings for receiver tubes able to overcome state‐of‐the‐art technological limitation in terms of both vacuum encapsulation and maximum operative temperature, currently limited at 550°C for molten salts CSP plants. To this aim, a multilayer structure was designed and developed for coating a receiver tube to be employed in open‐air environment at temperature of 600°C. The multilayer coating is based on tungsten chromium titanium infrared reflector and includes a solar absorber layer developed with two alternative methods of reactive sputtering and thermal oxidation respectively, finally covered by antireflective and barrier bi‐layer of aluminum oxide and silica. Thermal stability was demonstrated of the new developed coatings, since only small variations were measured of the optical parameters after more than 2000 h of aging in open air conditions at temperature of 600°C (on average less than 5%), with final measured solar absorptance αs of 73% and 87% and thermal emissivity εth at 600°C of 18% and 27% for aged multilayer structures including the absorber layer obtained through thermal oxidation and sputtering process, respectively. These results pave the way for further improvement in terms of both optical performance and operative temperature increase, allowing to enhance efficiency and lower costs, thus contributing to ease to deployment of CSP technology.

Vertical profiling of ultrafast carrier dynamics in partially strain relaxed and strained InGaN grown on GaN/sapphire template of different In composition

InGaN is one of the important ternary alloys which enables the nitrides to have bandgap energy in a wide range of 0.77–3.44 eV corresponding to the photon wavelength of 360–1610 nm by simply adjusting In content. However, the research on the InGaN has primarily focused on low-dimensional structures though knowledge of the physical properties of bulk InGaN thin-film is important in designing optoelectronic applications that utilize thick InGaN layers. In this study, we revisited partially strain relaxed bulk InGaN thin-films of different In compositions. We found that fast carrier decay was caused by hot carrier cooling due to the presence of oxygen impurity, and the slow carrier decay was governed by the carrier localization initiated by V-shape defects which concentrated at the bottom of the InGaN layer starting at InGaN/GaN interface. We also observed that the V-shape defects became severe, and the slow decay carrier lifetime decreased as In composition of the InGaN layer increased. Our observation gives guidance in designing optoelectronic applications using partially relaxed thick InGaN layers, such as buffer layers for long-wavelength InGaN light emitting diodes as well as solar absorber layer for InGaN photovoltaic cells.

Ternary atoms alloy quantum dot assisted hole transport in thin film polymer solar cells

Quantum confinement effects and multiple exciton generation (MEG) were explored in this investigation to assist the hole transport and improved trapping of light in thin film solar cells (TFOSCs). The popular organic transport material Poly (3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT:PSS) is employed here for effective electron blocking and hole transport processes through doping with quantum dots (QD). Alloyed CdTeSe QD is used, at different concentrations, in PEDOT:PSS layer to fabricate TFOSCs in the convectional device structure consisting of molecules blended as poly (3-hexylthiophene): (6, 6)-phenyl- C61-butyric acid methyl ester (P3HT: PCBM) solar absorber. A remarkable increase in performance of the devices was achieved from TFOSC whose HTL doped with QDs that resulted in an optimal boost in power conversion efficiency (PCE) as high as 111.7% relative to the reference cell. The results suggest that the doping of HTL with the alloy of CdTeSe quantum dots assisted in electron blocking, and improved hole collection as well as improved light trapping at the interface between the solar absorber layer and HTL.

Insights into post-growth doping and proposals for CdTe:In photovoltaic devices

This paper is motivated by the potential advantages of higher doping and lower contact barriers in CdTe photovoltaic devices that may be realized by using n-type rather than the conventional p-type solar absorber layers. We present post-growth doping trials for indium in thin polycrystalline CdTe films using the diffusion of indium metal with indium chloride. Chemical concentrations of indium up to 1019 cm−3 were achieved and the films were verified as n-type by hard x-ray photoemission. Post-growth chlorine treatment (or InCl3) was found to compensate the n-doping. Trial structures comprising CdS/CdTe:In verified that the doped absorber structures performed as expected both before and after chloride treatment, but it is recognized that this is not an optimum combination. Hence, in order to identify how the advantages of n-type absorbers might be fully realized in future work, we also report simulations of a range of p–n junction combinations with n-CdTe, a number of which have the potential for high V oc.

Characteristics of Al & Ti oxide-thin films for thermal solar energy selective absorption applications

Controlled oxidation of sputtered layers of Ti and Al results oxide layers with nano-sized thickness comparable to thermal solar selective absorber layers. In this work, RF magnetron sputtering was used to obtain thin layers of Al and Ti on substrates of stainless steels (St. St). Deposited thin films were oxidized at 400 °C and 800 °C for 4 hours and 1 hour, respectively. The as-deposited Ti, and Al layers were air–oxidized and their optical absorbance and emittance were studied. Microstructure, surface topography, structure and new phases formed after oxidation were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD). Thin films optical properties were investigated by spectrophotometer & Fourier Transform Infrared (FTIR) Spectroscopy. The new microstructures exhibited a dual metallic and oxide nature. Deposited thin film of Ti had maximum absorbance and lowest emittance about 90% and 1.8% respectively; while after oxidation, the deposited layers changed their selective absorbance pattern. The absorbance values increased, and the emittance values decreased for all wave lengths in the infrared (IR) range. The effect of the oxidation process of both Ti thin film and Al thin film was compared. The Al thin film showed lower absorbance in as-deposited and oxidized states.

Plasmon assisted optical absorption and reduced charge recombination for improved device performance in polymer solar cell

Silver and Calcium (Ag:Ca) bi-metallic nano-partices have been successfully synthesized using a chemical reduction processes. The nano-partices were intended to be used in the solar absorber layer of thin film organic solar cell (TFOSC) to assist in improving optical absorption and charge transport processes in polymers blend medium. The nanocomposite (Ag:Ca) is expected to exhibit local surface plasmon resonance (LSPR) and far-field scattering from the interaction with the incident photons. The absorber layer of TFOSC, in this investigation, is prepared from the mixture of poly-(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PC61BM). Devices were fabricated at various concentration of metal nano-particles in the solar absorber layer, as 1%, 3%, and 5% by weight, to be able to determine the optimum concentration of the dopant. Hence, the experimental evidences clearly showed that performance of the solar cell is dependent on the concertation of the metal nano-particles. Consequently, the power conversion efficiency (PCE) value has increased by 75% with a remarkable improvement in device fill factor of 53.4% at an optimum doping level of 3%. The optical and morphological properties of the synthesized nano-particles are well presented and discussed in terms of the data collected using transmission and scanning electron microscopy (TEM & SEM) and other complimentary methods.

Operation of Wearable Thermoelectric Generators Using Dual Sources of Heat and Light

A wearable thermoelectric generator (WTEG) that utilizes human body heat can be a promising candidate for the wearable power generators. The temperature difference (ΔT) between the body and the environment is a stable source driving the WTEG, but this driving force is limited by the ambient temperature itself at the same time. Here, a novel WTEG that can be operated using the dual source of body heat and light with exceptionally high driving force is fabricated. The printable solar absorbing layer attached to the bottom of the WTEG absorbs ≈95% of the light from ultraviolet to far infrared and converts it into heat. To optimize the power density of WTEGs, the fill factor of the thermoelectric (TE) leg/electrode is considered through finite‐difference time‐domain (FDTD) simulation. When operated by the dual sources, the WTEG exhibits a power density of 15.33 µW cm−2, which is the highest under “actual operating conditions” among all kinds of WTEGs. In addition, unlike conventional WTEGs, the WTEG retains 83.1% of its output power at an ambient temperature of 35 °C compared to its output power at room temperature. This study will accelerate the commercialization of WTEGs by introducing a novel method to overcome their limitations.

Effect of Annealing on the Structure, Morphology and Optical Properties of Co3o4 Thin Films as a Solar Absorber Layer

Effect of Annealing on the Structure, Morphology and Optical Properties of Co3o4 Thin Films as a Solar Absorber Layer

Effective energy harvesting in thin film organic solar cells using Ni:Zn as bimetallic nanoparticles

This article explores the effect of bimetallic plasmonic nanocomposites in the solar absorber layers of thin-film organic solar cells (TFOSCs) for possible improvement in harvesting solar energy. To achieve this goal, a new nanocomposite composed of Nickel and Zinc (Ni: Zn) was successfully synthesized by the use of a chemical reduction processes. The effect of bimetallic nanocomposites was studied using a photoactive medium, which comprises of poly-(3-hexylthiophene) (P3HT) [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) blend and doped with Ni:Zn at different concentrations. Consequently, an improved power conversion efficiency value up to 4.78% was found at 1% Ni:Zn bimetallic concentration by weight compared to reference solar cell. This is a clear indication of the influence of Ni:Zn bimetallic nanoparticles on the performance of TFOSC. These effects have been realized by the occurrence of local surface plasmon resonance (LSPR) phenomenon caused by Ni: Zn nanoparticles in polymer medium.

Metal nano-composite induced light trapping and enhanced solar cell performances

A tri-metallic nano-particles (NPs) involving Silver, Iron and Nickel (Ag:Fe:Ni) was successfully synthesized using a wet chemical reduction method. The synthesized nano-composite (Ag:Fe:Ni) has exhibited polycrystalline morphology in powder form, which was used as nano-composite in a P3HT:PCBM blend solar absorber layer of the thin film organic solar cell (TFOSC) to enhance the collection of photons. Consequently, the power conversion efficiency (PCE) of the thin film organic solar cells grew by 42% due to the incorporation of NPs in the devices structure. However, the concentration of metal nano-particles was varied from 0% to 3% by weight to determine the optimum doping level of the NPs for maximum effect in the solar absorbers. The effect of the metal nano-particles is clearly evident by high short circuit current (Jsc) of TFOSC which is attributed to improve the dissociation of exciton and charge transport processes in the medium. The optical and morphological characteristics of the nanoparticles were discussed in terms of the measured parameters.

Characteristics of Perovskite Solar Cells with ZnGa2O4:Mn Phosphor Mixed Polyvinylidene Fluoride Down-Conversion Layer

To reduce the manufacturing cost of perovskite solar cells, soda-lime glass and transparent conducting oxides such as indium tin oxide and fluorine-doped tin oxide are the most widely used substrates and lighttransmitting electrodes. However, the transmittance spectra of soda-lime glass, indium tin oxide, and fluorinedoped tin oxide show that all light near and below 330 nm is absorbed; thus, with the use of these substrates, light energy near and below 330 nm cannot reach the perovskite light-absorbing layer. It is expected that the overall solar cell can be improved if the wavelength can be adjusted to reach the perovskite solar cell absorbing layer through down-conversion of energy in the optical wavelength band. In this study, a polyvinylidene fluoride transparent film mixed with a ZnGa2O4:Mn phosphor was applied to the incident side of the perovskite solar cell with the intent to increase the light conversion efficiency without changing the internal bandgap energy and structure. By adding a phosphor layer to the external surface of PSC exposed to incident light, the efficiency of the cell was increased by the down-conversion of ultraviolet light (290 nm) to the visible region (509 nm) while maintaining the transmittance. To manufacture the perovskite solar cell, a TiO2-based mesoporous electron transport layer was spin-coated onto the substrate. The perovskite layer used in this experiment was CH3NH3PbI3 and was fabricated on a TiO2 layer. Spiro-OMeTAD solution was spin-coated as a hole-transport layer.

Self-contained Janus Aerogel with Antifouling and Salt-Rejecting Properties for Stable Solar Evaporation.

Janus structural interfacial vaporization by separating the solar absorber from the bulk working fluid has attracted tremendous attention due to its low heat losses and high solar conversion efficiency for desalination, water purification, energy generation, etc. However, a totally separated double-deck structure with a discontinuous interfacial transition and inefficient photothermic materials undermines its long-term use and large-scale practical exploitation. Herein, a low-cost Janus monolithic chitosan aerogel with continuous aligned run-through microchannels has been demonstrated to have a highly efficient photothermic effect on seawater desalination and wastewater purification. The top solar absorber layer enhances broadband light absorption and photothermal conversion efficiency via the multiple internal reflection of incident light in the aligned microchannels. Moreover, the insulating/hydrophilic bottom layer promotes water transportation and heat localization, and simultaneously prevents salt/fouling accumulation. As a result, a long-term solar vaporization rate of ∼1.76 kg m-2 h-1 is achieved, corresponding to a light-to-vapor efficiency of ∼91% under 1 sun irradiation. Notably, the large-vessel microchannels throughout the aerogel and favorable swelling property provide sufficient water replenishment and storage for completely isolating self-contained evaporation, illustrating an enhanced and time-extended self-contained solar steam generation. Such a low-cost bilayer aerogel with remarkable cycling stability in various fluids offers potential opportunities for freshwater production in remote rural areas.

The effect of bromide precursor on the properties of organolead halide perovskite for solar cell fabricated under ambient condition

Hybrid CH3NH3PbI3 − xBrx have drawn a tremendous interest as light harvesters in mesoscopic and planar heterojunction solar cells due to their high coefficient absorption. Herein, we investigated the difference between the effect of different bromide precursor on the properties of prepared CH3NH3PbI3 − xBrx thin film. In this study, the CH3NH3PbI3 − xBrx perovskite films were made by two processes. The first process consist in adding PbBr2 in the PbI2 with different molar ratios (x = 0, 0.05, 0.1) followed by depositing MAI in isopropanol. The second process resides in depositing CH3N3Br in isopropanol on the top of PbI2 − xBrx followed by dropping a solution of MAI in isopropanol. The study revealed that the prepared thin film using the first process with molar ratio 0.05 exhibited high crystallinity, suitable morphology, high absorption with non-radiative recombination. These attractive properties of the thin film prepared by the first process should heighten interest in its use as a solar absorber layer for increasing of solar cells efficiency.

Silver doped nickel oxide nanocomposite and photon harvesting enhancement in bulkheterojunction organic solar cell

Silver doped nickel oxide (Ag:NiOx) nanocomposites (NC) were synthesized using a thermal decomposition method for possible application in thin-film organic solar cells. Two different synthesis products were found from the experiment, which have exhibited different characteristics in terms of colour, structure, and optical properties. These nanocomposites (Ag:NiOx) have two distinct colours namely green and black. The green powder contains a trace of carbon element while the black powder is pure Ag:NiOx. Both products were used in device fabrication to assist in photons harvesting at a various concentration of the NC by weight. In all cases, an optimum concentration of 1 wt% of the Ag:NiOx powders were found to yield a maximum power conversion efficiency (PCE) of 4.9% and 5.1% for the green and black powders, respectively. Higher concentrations of Ag:NiOx in the solar absorber layers were found to be unfavorable in improving device performances. Overall, both synthesized metal NCs performed fairly similar and they have improved device performance substantially compared to the reference cells. The experimental results are discussed in terms of optical and electrical properties of the absorber layer as well as charge transport processes.