Incident Sunlight Research Articles

A transparent radiative cooling emitter with multi-band spectral regulation for building energy saving

The radiative cooling technology has gained momentum. Maximizing the reflection of incident sunlight has been the primary approach to enhance radiative cooling properties. However, the fully reflection and opacity of the proposed radiative cooling materials significantly limits their application scope. In this study, a transparent radiative cooling emitter was fabricated by optimizing the concentration of SiX nanospheres embedded in PVDF matrix. The emitter has the capability of multi-band spectral regulation, and exhibits outstanding performance in terms of visible light transmission, near-infrared reflectance, and selective infrared emission. In the cooling experiment, the temperature of the emitter was up to 8.5 °C and 15.1 °C lower than with commercial insulation thermal films and common glass, respectively. The emitter prepared by easy process has potential for large-scale production.

Thermal Moonquake Characterization and Cataloging Using Frequency‐Based Algorithms and Stochastic Gradient Descent

AbstractThermal moonquakes are recurring seismic signals detected on the lunar surface that are temporally correlated with the lunar day‐night cycle, although their precise mechanism is not known. The Lunar Seismic Profiling Experiment (LSPE) was a deployment of four geophones during the Apollo 17 mission to characterize the near‐surface structure of the landing site using explosive shots. The array was reactivated in passive recording mode several times after the mission was completed and recorded thousands of thermal moonquakes. In this study, we expand on an initial detection catalog and determine waveform parameters and source information for the seismic signals. We used a spectrogram‐based approach to obtain fine‐tuned arrival times, quantify the envelope length using emergence, and compute peak‐ground‐velocity. We obtain the incident azimuth direction by applying stochastic gradient descent to a travel‐time misfit equation. We found that thermal moonquakes are split into two main classes: (a) impulsive, high‐amplitude events that are produced by the lunar module descent vehicle located east of the LSPE array in response to rapid temperature transitions during sunrise and sunset and (b) emergent events, that are natural responses to incident sunlight whose duration is directly linked to the temperature of the regolith. We hypothesize that the correlation between temperature and emergence could be due to changes in regolith scattering or higher energy daytime events occurring further away.

Quantitative monitoring of salt stress in rice with solar-induced chlorophyll fluorescence

Under salt stress, rice leaves usually accumulate sodium and chloride ions, causing water loss. The consequent nutrition imbalance and damage to photosynthetic systems ultimately affects growth and development. Therefore, early identification of rice salt stress is important for timely amelioration to reduce rice yield loss. Solar-induced chlorophyll fluorescence (SIF) shows substantial effectiveness for its quick and sensitive response to early-stage stress, suggesting its potential for early crop stress detection. To further assess the capacity of SIF for salt stress detection, this study conducted field plot experiments with a single rice cultivar across two growth stages – jointing and booting. The leaf reflectance spectrum of rice was obtained using an ASD FieldSpec Pro FR portable field spectrometer (Analytical Spectral Devices, Boulder, Colorado, USA) and a leaf clip holder. The leaf solar-induced chlorophyll fluorescence (SIF) spectrum was obtained from an ASD coupling filter and FluoWat, which filters out incident sunlight beyond 650 nm. We calculated nine SIF yield indices (FYs), including ↑FY687 (upward fluorescence yield at 687 nm), ↑FY739 (upward fluorescence yield at 739 nm), ↓FY739 (downward fluorescence yield at 739 nm), totFY687 (total of upward and downward fluorescence yield at 687 nm), totFY739 (total upward and downward fluorescence yield at 739 nm). We also explored the adaptive regulation of three biological rice parameters under salt stress: the net photosynthetic rate (Photo), chlorophyll content (Chl), and maximum photochemical efficiency of photosystem II (Fv/Fm). Photo was the most sensitive to salt stress, and showed significant differences on the first day under salt stress. A salt stress response index (SSRI), which combines physiological and biochemical parameters, was constructed to describe the salt stress level. SSRI showed a significant difference on the first day of salt stress, and the dynamics of SSRI were consistent with that of Photo. In addition, we clarified the change rule of SIF for rice leaves under the salt stress. The gray correlation analysis identified five SIF fluorescence yield indices (FYs) that are highly correlated with SSRI: totFY739, ↓FY739, ↑FY739, totFY687, and ↑FY687. Based on the results of gray correlation analysis, a support vector regression model of SSRI was established, which gave an excellent result as follow: R2 of the calibration for the all dataset, booting dataset, and jointing dataset were 0.74, 0.74, and 0.70, respectively, and R2 of the validation data were 0.71, 0.73, and 0.68. In summary, the proposed method to quantitatively detect rice leaf salt stress based on SIF technology allows the early monitoring of rice leaf salt stress.

Environmental Effects on the Performance of Quantum Dot Luminescent Solar Concentrators.

Luminescent solar concentrators (LSCs) are all-photonic, semitransparent solar devices with great potential in the emerging fields of building-integrated photovoltaics and agrivoltaics. Over the past decade, particularly with the advent of quantum dot (QD) LSCs, tremendous progress has been made in terms of photovoltaic efficiency and device size by increasing solar spectral coverage and suppressing reabsorption losses. Despite these advances in LSC design, the effects of environmental conditions such as rain, dust, and dirt deposits, which are ubiquitous in both urban and agricultural environments, on LSC performance have been largely overlooked. Here, we address these issues by systematically investigating the environmental effects on the solar harvesting and waveguiding capability of state-of-the-art QD-LSCs, namely, the presence of airborne pollutants (dust), water droplets, and dried deposits. Our results show that dust is unexpectedly insignificant for the waveguiding of the concentrated luminescence and only reduces the LSC efficiency through a shadowing effect when deposited on the outer surface, while dust accumulation on the inner LSC side increases the output power due to backscattering of transmitted sunlight. Water droplets, on the other hand, do not dim the incident sunlight, but are detrimental to waveguiding by forming an optical interface with the LSC. Finally, dried deposits, which mimic the evaporation residues of heavy rain or humidity, have the worst effect of all, combining shading and waveguide losses. These results are relevant for the design of application-specific surface functionalization/protection strategies real LSC modules.

Experimental investigation of photovoltaic systems for performance improvement using water cooling

Abstract This research aims to analyse the comparative performance of two identical photovoltaic (PV) panels with load variations and integrating an automated water-cooling process under the climatic conditions of the United Arab Emirates. The work also presents the steps of system design, implementation and performance evaluation of the proposed PV system, and all electrical, control and mechanical components along with how they were integrated within a 100-W PV system. MATLAB®/Simulink® was used only to simulate the behaviours of the PV panel under wide ranges of incident sunlight and ambient temperature. The tests were performed for a day-long operation during a clear summer day. The experimental results demonstrate an improvement in the PV system performance compared with the uncooled system by ~1.6% in terms of total harvested energy using the proposed water-cooling process with a frequency of 2 minutes of cooling operation every 30 minutes during day hours.

Efficient Photovoltaic Unit for Power Delivering to Stand-Alone Direct Current Buildings Using Artificial Intelligence Approach Based MPP Tracker

There are many remote buildings that cannot be supplied by alternating electricity of the utility grid. Due to this, this study proposes adopting Direct Current (DC) appliances for a stand-alone remote building. Direct Current can be supplied from a suitable photovoltaic array which can harvest renewable solar energy. This proposal guarantees an efficient power system by removing the necessity of including an inverter, power filter, insulation transformer, and a complicated controller, which are usually needed for producing Alternating Current (AC) power to feed AC loads using a PV system. When the proposal is applied, the PV system will be more efficient, simple, affordable, and more compact. A detailed power requirement calculation for a typical house uses DC appliances, generalized steps to design a suitable PV array, and an Artificial Neural Network (ANN) algorithm for guaranteeing Maximum Power Point Tracking (MPPT); all of which are introduced for remote buildings. The main contribution of this paper is proposing an integrated design of a DC unit of 11 kW·h PV system for stand-alone buildings that eliminates three stages that improves the system performance compared to AC unit. The introduced study includes PV array calculation based on PV module of 220 W with an intelligent algorithm of four layers. The Mean Squared Error (MSE) of the proposed ANN equals 2.7107 × 10−5 to guarantee a fast and accurate MPP tracking for continuously harvesting maximum power from the incident sunlight. An energy storage unit of 12 batteries 12 V/150 Ah of matrix dimensions 3 × 4 is designed in the DC unit for energy saving to feed the DC appliances during night hours. MATLAB/Simulink Version R2015b is used to simulate the introduced DC power unit and collect the testing records for analyzing the unit performance.

Evaluation the spectral reflectivity of Baghdad city for different bands using R.S and GIS techniques on December 2021

The rapid advancement of remote sensing technology in recent years has made it easier to observe and study the Earth’s surface with greater precision. Satellite remote sensors have poor spatial accuracy and cannot provide accurate details of targets on the Earth’s surface. As a result, spectral accuracy is required to determine target details such as water, vegetation and soil types. Because of the differences in spectral reflectivity, these materials can be distinguished. The amount of randomly incident sunlight scattered on the Earth’s surface at a given wavelength is reflected in spectral reflection with different wavelengths. The amount of light reflected on the Earth’s surface varies, the spectral reflectivity is defined as the ratio of the spectral intensity of the reflected light to the incident light. In this study, 51 locations in downtown Baghdad were chosen for four different types of land cover (water bodies, farms, open areas, and residential areas), and their spectral reflectance was calculated on three different bands (RED, NIR and SWIR) for December 2021. The spectral reflectance was calculated using a mathematical equation using Sentinel 2 satellite images that had been processed and analyzed.

Extreme-environment tolerant superhydrophobic montmorillonite/hollow SiO2 composite coating as building radiative cooler for scale energy conservation

Passive radiative cooling (PRC), as a promising energy-saving strategy can obtain sub-ambient cooling by reflecting solar irradiation and dissipating excessive heat to outer space without any energy consumption. However, for outdoor environment, especially extreme environment, the cooling performance of PRC materials may be affected by dust pollution and acid-alkali corrosion. Herein, we proposed a superhydrophobic radiative cooling composite coating prepared by modified montmorillonite (MMT) and hollow SiO2 (H-SiO2) for all-day cooling with low-cost raw materials. Due to stronger backscattering of hollow structure, this coating can effectively reflect incident sunlight, accounting for the high solar reflectivity (0.93) and the mid-infrared emittance (0.94) originated from the combination of MMT and H-SiO2. Subsequently, it exhibits satisfied cooling performance with the temperature drop of 4.1 ℃ under an averaged solar irradiation of 1020 W/m2 in the daytime and 6.2 ℃ in the nighttime. Moreover, the superhydrophobic surface of the coating prevents the dust pollution and the corrosion of acidic and alkaline solutions, broadening its application in the extreme environment. Thereby, our work lights a path on the novel energy-saving coating for extreme environment.

Robust direct solar water production by integrating interfacial evaporation and membrane distillation

Interfacial solar vapor generation (ISVG) is an important technique for producing water with a minimal carbon footprint. For customers who need a lot of water, the state-of-the-art ISVG devices are unbearable and unacceptable because of their low condensation capacity. This paper introduces a novel configuration that integrates ISVG and direct contact membrane distillation (DCMD) devices to increase the water yield. A carbon nanoparticle-based solar absorber that can collect 94.6 % of incident sunlight and has a substantial water supply capacity is employed for ISVG. For high vapor permeability, moreover, a hydrophobic polyvinylidene fluoride membrane with a moderate pore structure is adopted. The result shows that the ISVG-DCMD device has a water productivity of up to 2.71 kg m−2h−1 under 2 sun illumination. More importantly, the system has a sustainable water productivity of 2.08 kg m−2h−1 when operating in NaCl solution with a concentration of 3.5 % (w/w). This work effectively solves the problem of vapor condensation of the interfacial photothermal evaporator, offering a novel concept for scalable and robust direct solar water production.

Elastocaloric cooler for waste heat recovery from perovskite solar cell with electricity and cooling production

To realize sufficient use of incident sunlight, a novel coupled system involving a perovskite solar cell (PSC) and an elastocaloric cooler (ECC) is established, with the ECC applied to thermally utilize the portion of long wavelength photons unconverted by the PSC. A theoretical model of the proposed system is developed, taking into account various irreversible losses, from which the availability and efficiency of the system is tested. Mathematical expressions for the key performance indicators of the subsystem and coupled system are deduced, and the numerical calculations indicate that the peak output power and its corresponding efficiency of the coupled system are improved by 23.25% and 23.17% compared to the stand-alone PSC, respectively. Furthermore, comprehensive sensitivity analyses are undertaken to derive the effects of critical designing parameters and operating conditions on the overall performance, including operating temperature, perovskite layer thickness, length ratio, Young's modulus ratio, Clausius-Clapeyron coefficient ratio, and the transformation strain ratio. The findings of this study may offer some guidelines for further improving PSC properties with cogeneration technology.

Row orientation influences the diurnal cycle of solar-induced chlorophyll fluorescence emission from wheat canopy, as demonstrated by radiative transfer modeling

Although multiple studies have used solar-induced chlorophyll fluorescence (SIF) of the crop canopy to estimate photosynthetic activity, the effect of canopy geometry (row orientation) on diurnal SIF remains uncertain. Using a combination of 3D canopy radiative transfer modeling and spectroscopic observations collected in a winter wheat field, we investigated (i) the relationships between observed SIF and factors including temperature, humidity, absorbed photosynthetically active radiation (APAR), and row orientation; (ii) the temporal pattern and multi-angle distribution of diurnal canopy SIF; and (iii) the mechanisms influencing components of diurnal SIF under the effect of row orientation. The relationship between observed SIF and APAR was relatively strong at the early growth period, but SIF was influenced by various factors (temperature, humidity, and row–sun angle) at the middle of the growth period. To test an asymmetric crop row effect as a potential cause of this skewness, we evaluated the modeled SIF with a 3D northwestward (315°) crop row alignment and other orientations. Each row orientation resulted in a trough-like depression parallel to the row in simulated canopy SIF, which could cause a diurnal asymmetry of canopy SIF, a fraction of fluorescence escape, and a fraction of APAR. View angles, the dimension of canopy objects (1D/3D), inter-row width, and leaf structure parameters impacted the representativeness of these simulations. An increased shade SIF, synchronized with the time when row–sun angles become zero at the incident sunlight being parallel to the crop row, was linked to decreasing canopy SIF emissions and would cause a non-linear SIF–APAR relationship at certain row orientations especially facing diagonally to the south. The concept of row orientation provides a novel viewpoint of diurnal canopy SIF from which to test the effect of row geometry in cropland, and will promote a mechanistic understanding of photosynthesis and canopy light use.

Solar Thermoelectricity for Power Generation

AbstractThermoelectric materials convert waste heat into electricity, making sustainable power generation possible when a temperature gradient is applied. Solar radiation is one potential abundant and eco‐friendly heat source for this application, where one side of the thermoelectric device is heated by incident sunlight, while the other side is kept at a cooler temperature. This is known as solar thermoelectric generation. Various thermoelectric materials are used for different solar thermoelectric applications, and different methods are explored to enhance the temperature gradient across the material. Solar optical concentrators, thermal and selective absorbers, and other tools are proposed to improve the performance of solar thermoelectrics. Despite continuous research and development, experimental solar thermoelectric efficiencies remain below 10%, and theoretical efficiencies do not surpass 20%. In this review, the different designs of solar thermoelectric generators are examined within the context of thermoelectric elements, optical concentrators, solar absorbers, and other techniques to enhance their performance. Last, an overview of the current state of solar thermoelectrics is provided, areas for improvement are suggested, and the future of these devices is predicted.

Effect of scattering angle on DSCOVR/EPIC observations

The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) routinely captures reflected radiation from the whole sunlit side of the Earth in the near backward direction to monitor the changing planet. The instrument had routinely operated until 27 June 2019, when the spacecraft was placed in an extended safe hold due to degradation of an inertial navigation unit. DSCOVR returned to full operations on 2 March 2020. Since then, the range of scattering angles between the incident sunlight and sensor direction has been larger than before and the largest scattering angle reaches ∼178°, only 2° from perfect backscattering, proving a unique opportunity to study the top-of-atmosphere (TOA) reflectance under such extreme conditions. In the paper, we compare EPIC global spectral reflectances in 2021–2016. We found that there are four occasions when the scattering angle reaches about 178° and associated with them enhanced global daily average spectral reflectances in 2021. The scattering angle related reflectance enhancements are not found in 2016 data when the maximum scattering angle is about 174.5°. CERES data do not show such occasions in global daily reflected shortwave flux. As a result, those enhanced reflectance occasions are primarily due to the change in scattering angle. The enhancement due to changes in scattering angle depends strongly on wavelength, primarily because of wavelength dependence of cloud scattering phase function. Radiative transfer calculations show that the change in scattering angles has the largest impact on reflectance in the red and NIR channels at 680 nm and 780 nm and the smallest influence on reflectance in the UV channel at 388 nm, consistent with EPIC observations. The change of global average cloud amount also plays an important role in the reflectance enhancement. The influence of the cloud effect depends on whether the change is in phase or not with the change of scattering angle.

A Review on Solar Photovoltaic Technology and Its Future Trends

A source of radiant energy is the Sun. Only a small part of the energy we receive from the Sun is actually used by us. Sunshine that reaches the surface of the Earth has the capacity to meet all of our rising energy needs. The process of converting incident sunlight energy into electrical energy is known as solar photovoltaic technology. The original generation of solar cells were made of silicon. Further advancements are required, according to research, for solar cells to operate more efficiently and to absorb large amounts of incident sunlight. To achieve these requirements, amorphous Silicon sola r cells and thin film technology were further developed. From first-generation solar cells to dye-sensitized solar cells, quantum dot solar cells, and some more current technologies, we have examined a gradual progression in solar cell technology in this review. The potential for these many generations of solar cell technologies to establish themselves is also discussed in this article. Keywords: Solar Photovoltaic, Dye sensitized solar cells, Quantum dot solar cells, Tandem solar cells, Hybrid Perovskite solar cell.

Solar-Driven Production Of Hydrogen Peroxide And Benzaldehyde In Two-Phase System By An Interface-Engineered Co9 S8 -CoZnIn2 S4 Heterostructure.

Coupling the photoproduction of solar fuel and value-added chemicals is highly attractive, as it maximizes the utilization of incident sunlight and the economic value of photocatalytic reactions. Constructing intimate semiconductor heterojunction for these reactions is highly desirable due to accelerated charge separation at the interfacial contact, but is challenged by material synthesis. Here, an active heterostructure bearing intimate interface, consisting of discrete Co9 S8 nanoparticles anchored on cobalt doped ZnIn2 S4 using a facile in situ one-step strategy, can drive photocatalytic co-production of H2 O2 and benzaldehyde from a two-phase water/benzyl alcohol system with spatial product separation is reported. The heterostructure yields a high production amountof 49.5 and 55.8mmolL-1 for H2 O2 and benzaldehyde under visible-light soaking, respectively. The synchronous elemental Co doping and intimate heterostructure establishment substantially improve the overall reaction kinetics. Mechanism studies reveal that H2 O2 generated in the aqueous phase undergoes photodecomposition forming hydroxyl radical, which is subsequently transferred into the organic phase to oxidize benzyl alcohol into benzaldehyde. This study offers fertile guidelines for creating integrated semiconductors and broadens the avenue toward the coupled production of solar fuels and industrially important chemicals.

Numerical performance investigation of a photovoltaic-thermal hybrid collector-evaporator with different tube configurations for heat pumps

Surface temperature build-up due to the continuous conversion of incident sunlight to heat deteriorates the power output, efficiency, and life of photovoltaic panels. Photovoltaic-thermal (PV-T) systems provide a potential solution to avoid excessive heating of PV panels, simultaneously providing useful heat energy. A heat extraction unit is attached to the PV panel in PV-T systems that extract and convert the waste heat into useful heat. Therefore, design and material selection are keys to better performance in the system-level approach. Additionally, it is a cumbersome task dealing with refrigerant-based heat and fluid flow interactions in a system-level approach. With this in perspective, this paper analyzes different materials and flow configurations of PV-T systems. A transient, three-dimensional turbulence solver coupled with heat transfer through solids and liquids physics is modeled using COMSOL Multiphysics software. R-32 refrigerant acts as the heat transfer fluid in the system loop. The conservation equations are discretized using the finite element method. The present study involves two different plate materials (aluminum and copper) and three flow configurations (serpentine, roll-bond, and spiral) with and without absorber plates. A total of eight different configurations are being investigated here. The obtained results suggest that with the absorber plate, the performance increases significantly with a PV panel temperature decrease of 4–5 K, and the outlet fluid temperature increase by 2–8 K. It was observed that the performance difference between copper and aluminum plate is minimal (2%). Roll-bond flow configuration has scope for further research since it is more efficient than others because of the larger contact area for heat transfer.

A flexible PDMS@ZrO2 film for highly efficient passive radiative cooling

Passive daytime radiative cooling (PDRC) technology can make objects cooling down without energy consumption by radiating out heat through the atmospheric transparent window (ATW, 8–13 μm) and simultaneously reflect incident sunlight to avoid heated. In this work, a flexible radiative cooling film (FRCF) was fabricated by embedding zirconium dioxide (ZrO2) particles into polydimethylsiloxane (PDMS). It exhibited a high emissivity over 0.95 in ATW and a high reflectance beyond 0.92 in range of visible light. It achieved better cooling performances and yields an average temperature drop of 16.1℃ compared to the air around the film under the solar intensity of 735 W/m2. Because of its good cooling performance, great flexibility and acid resistance, this FRCF will have a wide application of radiative cooling in buildings and equipment.

Preface

Green energy refers to energy that can be directly used in production and life. It includes nuclear energy and renewable energy. With the continuous growth of energy demand and the increasing awareness of environmental protection in the countries around the world, it is urgent and imperative to establish a green energy innovation research and development, promotion and application system, and electricity will play a huge role in the development of green energy.2023 2nd International Conference on Green Energy and Power Systems (ICGEPS 2023) was held virtually under such a background in Changsha, China on January 6th to 8th, 2023. The aim of the symposium was to provide an opportunity for international experts, academics, researchers, practitioners and students working in the areas of green energy and power system to exchange information on the R&D and commercialization of green energy and power system. New developments, concepts, future research trends and potential commercialization areas were also discussed.The topics covered in the proceedings of ICGEPS 2023 are as follows: Power Systems and Its Automation, Measurement Technology and Instrumentation, Sensors and Micro Machines, Clean Energy Technology, Sustainable Coal Utilization and Clean Coal Technology, etc. Approximately 100 experts and scholars from almost 10 countries participated in the conference. The conference featured keynote speeches, oral presentations, and poster presentations.During the keynote speech part, three well-known professors delivered expertise lectures by imparting the latest findings from their respective research domains. Among them, Prof. Chong Kok Keong from Universiti Tunku Abdul Rahman, Malaysia addressed a keynote speech on Performance Analyses of Photovoltaic Module under Different Spectral Irradiances by Considering both Photonic and Electrical Characteristics. The solar spectral irradiance varies significantly for different locations and time due to latitude, humidity, cosine effect of incident sunlight, etc. To predict the actual performance of photovoltaic module under local climate conditions, he and his team proposed a methodology to compute the power-conversion efficiency of organic photovoltaic cells based upon indoor measurement with a solar simulator, the measured local solar spectrum, and making use of both optical and electrical factors. It was a wonderful opportunity for all the participants to interact with the experts and specialists to get their advice or suggestions.We would like to express our gratitude to all the participants for their presentations and discussions, which made the conference very successful indeed. We are also grateful to the Conference Chair, the Program Committee Chair, the Publication Chair, the Organizing Committee, and the Technical Program Committees for their fruitful work. We would like to express our thanks to all the authors for their time and genuine efforts, and to the reviewers for their fruitful comments during the preparation of this volume.The Committee of ICGEPS 2023List of Committee Member is available in this pdf.

Evolution of the microstructure and reflectance of the surface scattering layer on melting, level Arctic sea ice

The microstructure of the uppermost portions of a melting Arctic sea ice cover has a disproportionately large influence on how incident sunlight is reflected and absorbed in the ice/ocean system. The surface scattering layer (SSL) effectively backscatters solar radiation and keeps the surface albedo of melting ice relatively high compared to ice with the SSL manually removed. Measurements of albedo provide information on how incoming shortwave radiation is partitioned by the SSL and have been pivotal to improving climate model parameterizations. However, the relationship between the physical and optical properties of the SSL is still poorly constrained. Until now, radiative transfer models have been the only way to infer the microstructure of the SSL. During the MOSAiC expedition of 2019–2020, we took samples and, for the first time, directly measured the microstructure of the SSL on bare sea ice using X-ray micro-computed tomography. We show that the SSL has a highly anisotropic, coarse, and porous structure, with a small optical diameter and density at the surface, increasing with depth. As the melting surface ablates, the SSL regenerates, maintaining some aspects of its microstructure throughout the melt season. We used the microstructure measurements with a radiative transfer model to improve our understanding of the relationship between physical properties and optical properties at 850 nm wavelength. When the microstructure is used as model input, we see a 10–15% overestimation of the reflectance at 850 nm. This comparison suggests that either a) spatial variability at the meter scale is important for the two in situ optical measurements and therefore a larger sample size is needed to represent the microstructure or b) future work should investigate either i) using a ray-tracing approach instead of explicitly solving the radiative transfer equation or ii) using a more appropriate radiative transfer model.

The Properties of the CH3NH3PbI3/TiO2 Composite Layer Prepared from PbO-TiO2 Mesoporous Layer under Air Ambience

In TiO2-based perovskite solar cells (PSC), the preparation of the CH3NH3PbI3/TiO2 composite layer is very important, since the morphology of the perovskite adsorbed onto the surface of the TiO2 nanoparticles has decisive significance for the absorption of the incident sunlight and separation of the generated carrier. The traditional two-step spin-coating method for the deposition of CH3NH3PbI3 into the porous mesoporous TiO2 layer usually suffers from filling block problems. In this study, the PbO-TiO2 mesoporous layer was prepared with various ratios of Pb:Ti in the raw materials. Morphological, optical, and element analysis of the prepared thin films indicated that Pb was gradually mixed into the TiO2 mesoporous layer with the increased Pb:Ti ratios. The element distribution characteristics of the optimal thin films showed that the distribution of Pb was uniform throughout the whole TiO2 thin film, which indicates the successful mixing of Pb into the TiO2 electrode layer. Combined with dip coating, the PbO-TiO2 mesoporous layer was prepared into a CH3NH3PbI3/TiO2 composite layer and subsequently to a solar cell device. The prepared solar cell shows a short-circuit photocurrent density of 16.4 mA/cm2, an open-circuit voltage of 900 mV, a fill factor of 61%, and a power conversion efficiency (PCE) of 9.00%. The PCE of the PSC is promoted by nearly 25% when compared with that prepared with the traditional method. The proposed preparation method that combines TiO2 nanoparticle electrode with a mixing and dip coating provides a new effective way to improve the deposition of perovskite into the mesoporous TiO2 layer, which is very helpful for the fabrication of high-efficiency and low-cost PSC.