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A unique procedure to model and simulate a 36-cell-50 W solar panel using analytical methods has been developed. The generalized expression of solar cell equivalent circuit was validated and implemented, making no influential assumptions, under Simulink/MATLAB R2020a environment. The approach is based on extracting all the needed parameters by exploiting the available parameters from the data sheets of commercial PV panels and by estimating the slopes at both short-circuit and open-circuit conditions of the current–voltage characteristic, usually provided by most solar panels manufacturers under standard test conditions (STC). The effects of solar irradiance and temperature were both considered in the modeling. A system of coupled nonlinear simultaneous equations for diode saturation current, diode ideality factor, and series and shunt resistances has been solved. To accurately model the PV module used in our simulation and analysis, the needed temperature- dependent parameters have been extracted for the first time. At STC irradiance of 1000 W/m2, the modeled I-V curve was found identical to the experimental one which is provided by the solar panel manufacturer. The maximum power output of the PV module increases from 8.75 W to 50 W when irradiance varies from 200 W/m2 to 1000 W/m2 at STC temperature. At temperatures higher than STC and for the same solar irradiance, the power output of the PV module came down about 14.5% only when the operating temperature reached a value of 65 °C. However, as temperature is below STC, the power output went up of about 7.4% beyond the maximum power of the rated PV panel. The calculated power temperature coefficient was about −0.39%/ oC which is quite close to the one provided by the solar panel manufacturer.

Compared with monofacial photovoltaic (PV) modules, the output power of bifacial modules is higher since they can utilize additional sunlight of backside. Therefore, the backside irradiance distributions have a great influence on the performance of the bifacial modules. In this article, the backside irradiance distributions of the bifacial PV modules were studied according to the view factor models. Based on irradiance nonuniformity of the PV module backside and single diode model of solar cell equivalent circuit, the micromismatch losses were calculated by the IV curve superposition method. In addition, simulations and experiments of the backside irradiance nonuniformity is designed in Changzhou, China, to verify the theoretical calculation model. According to simulation and experiment result, the micromismatch losses of bifacial modules under different conditions (including grassland, cement floor, snowfield, with and without crossbeam) were analyzed. In the simulation, the micromismatch loss of bifacial PV module in PV system is less than 3%, which depends on field surrounding ground of PV modules. The losses in grassland, cement floor, snow ground is 0.3%–0.5%, 0.5%–1%, 1%–3%, respectively. Due to the shadows of PV module mounting frame, the micromismatch loss will increase by 0.5%–3.3%.

The article outlines the problems of reducing the efficiency of solar modules and their degradation due to overheating of surfaces in working conditions at elevated temperatures. It is shown that the temperature coefficient of power depends on environmental conditions, the type and material of solar cells and their quality and determines the degree of degradation of solar modules. Options for improving the reliability and durability of solar modules due to the correct choice of module installation locations, the use of high-quality modules and films protecting devices from mechanical damage and pollution are given. Based on the solar cell equivalent circuit, the basic energy parameters of the solar module are calculated. It was found that the short circuit current is practically independent of the ambient temperature and the surface heating of the module. The output power of the solar module is proportional to the voltage, which largely depends on the heating temperature of each solar cell. To maintain the efficiency of the solar module near the point of maximum power, it is necessary to provide thermal protection of the surface from the influence of high temperatures. A structural calculation scheme has been drawn up taking into account external parameters that affect the operational parameters of the modules, in which thermal protection of its surface is an important element in calculating the energy characteristics of solar modules.

In this paper, a scaling study of heterojunction solar cells based on p-type silicon quantum wires with rectangular cross sections in the sub-10-nm regime and graphene (p-SiQWs/G) is presented. The scaling issues in p-SiQWs/G solar cells performance focusing on SiQWs diameter, the distance between SiQWs, and the number of graphene layers is investigated by a coupled optical and electrical model taking into account the quantum effects of SiQWs. A minimum efficiency of p-SiQWs/G solar cells is obtained for SiQWs with moderate diameter. The p-SiQWs/G solar cell with small diameter shows high efficiency because of wide band gap of SiQWs with small diameter. On the other hand, p-SiQWs/G solar cell with large diameter also shows high efficiency because of strong light absorption of SiQWs resulted from high surface area. The results also show that the denser packing of SiQWs and monolayer graphene improve the efficiency of p-SiQWs/G solar cells.

Perovskite solar cells are considered as an up-and-coming substitute for the next generation solar cells. Despite of significant increase of its photon-electric conversion efficiency, a definitive direction for further increment remains ambiguous. In this paper, we quantitatively assess the energy losses in planar perovskite solar cells in terms of the underlying physical mechanisms. The coupled optical and electrical modeling is developed to explore the working principle of the perovskite solar cells. A comparison between simulation results and experimental data under different operating conditions is investigated to elucidate the reliability of the device modeling. With the aid of the accurate device modeling, we explore the energy loss mechanisms in planar perovskite solar cells. Five energy loss mechanisms are quantified, such as thermalization loss, below bandgap loss, optical loss, recombination loss, and spatial relaxation loss. The effects of the optical properties, carrier diffusion length, surface recombination velocity, and series resistance on the performance of the perovskite solar cells are analyzed to identify the dominant loss contributors limiting the power conversion efficiency of the perovskite solar cells. Our results indicate that more efforts should be paid to enhance the optical absorption of the perovskite layer, improve the surface passivation, and reduce the series resistance. Based on the theoretical analysis, a roadmap to promote the device performance of the perovskite solar cells is summarized. Our work provides a detail guideline for design and innovation of perovskite-based device.

The use of p-type silicon (p-Si) as hole transport materials (HTM) has been suggested to enhance the stability of perovskite-based solar cell (PSC). We design and simulate the CH3NH3PbI3/p-Si planar heterojunction perovskite solar cell and the power conversion efficiency exceeding 18%. In the solar cell, the metal electrode work function of perovskite solar cells is a decisive factor for built-in voltage (Vbi). The device simulation revealed that the Vbi and VOC increases when rear electrode work function (фM−rear) decreasing from −4.3 eV to −4.7 eV, the Vbi almost saturate to the plateau and the performance is optimal when фM−rear = −4.8 to −5.2 eV. However, the work function of the front electrode (фM−front) also has a significant effect on the performance of p-Si perovskite solar cell. When фM−front decreasing from −3.4 to −4.0 eV, a higher performance can be obtained and the Vbi almost saturate to the plateau. The results showed the importance of the фM matching to maintain Vbi, which is useful guideline for the design of the p-Si perovskite solar cell.

In a single-bandgap solar cell, efficiency is limited by the inability to efficiently convert the broad range of energy that photons possess in the solar spectrum. One of the effective ways of enhancing the efficiency of solar cells is to split the broad solar spectrum into smaller energy ranges and to utilize each range with a photovoltaic (PV) cell of the appropriately tuned bandgap. The conventional approach to implementing this idea is to use stacks of PV cells sequentially placed in the order of increasing bandgap energy, with the highest bandgap cell at the top. Lateral spectrum splitting can avoid many of the disadvantages of this conventional approach. We demonstrate that spectrum splitting with a prism and a lens can achieve enhanced efficiency with a combination of GaAs and c-Si solar cells.

Maximizing the conversion of sunlight to electricity by theoretically optimizing the utilization of lattice-matched multi-junction photovoltaic cells of the incident solar radiation was attempted. The lattice constant matching among the layers is important to avoid the internal thermal stress. In the proposed model the current mismatching, the thermalization losses, and the fill factor were all introduced to the conversion efficiency equation. The current matching can be achieved not only by suitable choice of bandgap energies, which directly decides the photon count distribution among the junctions, but also, by the absorbed amounts of those photons that could be controlled effectively by optimal choice of thicknesses; which is the significance of this research since such additional design freedom is essential to overcome the possible imperfect choice of bandgap energies that is dictated by the lattice matching requirement. Numerical search method was employed to find the optimal thicknesses for two- and three-junction PV solar cells in order to maximize the conversion efficiency. The performance of the proposed model is tested for various lattice-matched MJ samples. The results revealed that employing well-chosen bandgap energies for the active media in these samples leads to promising and efficient electricity generation using MJ solar cells. For example, 41.6% and 46.7% solar to electricity conversion efficiency can be obtained from double and triple junction solar cells, respectively, under concentrated sun regime.

A solar cell device architecture with top-illumination, where the light does not pass through the substrate, is advantageous for many applications. It is also specifically useful for the construction of tandem or multiple junction photovoltaic devices, with illumination through the top solar cell. Here, a top-illuminated colloidal quantum dot solar cell (TI-CQDSC) is demonstrated and compared with a conventional colloidal quantum dot solar cell (C-CQDSC) constructed on a FTO (fluorine doped tin oxide) glass substrate both theoretically and experimentally. The optical electric field distribution in the solar cells with different configuration is simulated using transfer matrix formalism and a more intense optical electric field was observed in TI-CQDSC, leading to a higher exciton generation rate within the colloidal quantum dot solid. The TI-CQDSCs are constructed on both nonconductive glass and flexible substrates, and a maximum power conversion efficiency of 6.4% and 5.6% is achieved, respectively, comparing to that of 5.9% for the C-CQDSC. The improved performance of the top illuminated solar cell is attributed to a combination of enhanced optical electric field intensity in the colloidal quantum dot solid and superior conductivity of the transparent metal film electrode.

The solar flux distribution on the receiver of a solar power tower is usually not uniform, which can cause a number of problems for the energy efficiency and system safety, particularly, the local hot spot and the thereby caused thermal stress and thermal deformation. Therefore, homogenization of the solar flux distribution is critical and important. The objective of the present study is to homogenize the solar flux distribution while keeping the optical loss (reflection loss) as low as possible through optimization of the distribution of the solar absorptive coating. An integrated approach coupling the Monte-Carlo ray tracing method and the Gebhart method is applied to simulate the process of the solar radiation transfer in the solar power system. The multi-objective optimization of the distribution of solar absorptivity is performed by using the non-dominated sorting genetic algorithm. The following conclusions are drawn from the study. (1) The improvement of the uniformity of the distribution of solar flux can lead to more reflection loss due to the fact that more solar energy is distributed on the position with greater view factor to the aperture; (2) The Pareto optimal front obtained from the multi-objective optimization provides the trade-off between the non-uniformity of the solar flux distribution and the reflection loss. (3) The optimal solar absorptivity distribution provided by the Pareto optimal front can significantly flatten the solar flux distribution at a minimum cost of optical loss. (4) The optimal distribution of the solar absorptivity is approximately opposite to the distribution of solar flux projected onto the active surfaces from the heliostat fields.

In this work, advanced photon-management composite subwavelength structures are fabricated to manage solar energy in the full-spectrum (300–2500 nm) wavelength range for the application of the photovoltaic-thermoelectric hybrid systems to fully utilize the solar energy. This proposed photon-management method will simultaneously realize efficient light trapping for the photons with above-bandgap energy in solar cells and the utilization of the below-bandgap photons and the waste heat resulting from the thermalization effect in solar cells with bottom thermoelectric devices. The typical structure is designed: Top ordered hexagonal nanohole arrays can trap above-bandgap photons to enhance the absorption in the silicon wafer, and TiO 2 /SiO 2 bilayer films are deposited on the bottom side of the wafer to improve the transmission of the below-bandgap photons. ∼97% total absorptance for wavelengths of 300–1100 nm is achieved with optimized diameters of central nanoholes. The total transmittance, on the other hand, is improved to ∼60% from 1200 nm to 2500 nm. The results indicate that the structures realize the appropriate allocation of photons within different wavelength ranges to different devices for sufficient utilization of full-spectrum solar energy. This novel full-spectrum photon management benefits from the strong scattering effect among the nanoholes and the gradient refractive index of bilayer films. Moreover, the photon-management performance shows angle-independent and polarization-insensitive characteristics. This method can be applied to various kinds of solar cells for photovoltaic-thermoelectric hybrid systems and may provide thoughts for other solar harvesting applications.

Comparative study of GaAs and CdTe solar cell under low-intensity light irradiance was carried out to study the cell device performance in response to the changed light irradiance intensity. For highly efficient GaAs solar cell, the series Rs and the shunt Rp resistance were found to be low/high enough to have almost undetectable negative effect on the cell device performance at low-intensity light irradiance. The robust diode parameters guaranteed good cell performance at low-intensity light irradiance. An ideal logarithmic function was established to describe the variation of cell efficiency with light irradiance intensity for GaAs solar cell. For CdTe polycrystalline solar cell, the relatively large series resistance Rs and small shunt resistance Rp, compared to that of the GaAs solar cell, significantly decreased the cell fill factor. With increased light illumination intensity, both the diode ideality factor A and the reverse saturation current density J0 were increased due to the high density of interface states at the CdS/CdTe junction. The comparative study and conclusions drawn in this work provide device fabrication improvement direction for the CdTe solar cell.

High-efficiency silicon solar cells are well known to have high “capacitance,” in the sense of having a slow time response to changes in voltage or current. This is often seen during power measurements of cells or modules. This issue is increasingly important as high-efficiency cells such as p -type passivated-emitter rear contact (PERC) and n -type heterojunction cells become more common within the industry. A fundamental understanding of solar cell device physics is essential to evaluate the various test methods used to accurately measure device power output under transient conditions during flash testing. This paper offers a simple device physics framework that is sufficient to understand a wide variety of test conditions and evaluate test solutions for cell or module output power measurements.

The effective use of solar energy has become significantly important due to unnatural weather changes and fossil fuel exhaustion. Concentrating Solar Power (CSP) technology is a promising approach to harvest solar energy in the form of heat using solar selective absorber coating. These coatings are expected to absorb maximum incoming solar radiation (α ≥ 0.95) and prevent loss of the absorbed energy as infrared radiation (e ≤ 0.05). Efficiency of the absorber coating can be evaluated by a metric called “Solar selectivity (α/e)”. In recent years, a number of attempts have been made to achieve remarkable selective property and high temperature stability of the absorber coating using the concept of Surface Plasma Polaritons (SPPs). The SPPs have the capability to capture solar energy by confining electromagnetic field at the metal-dielectric interface. Solar absorption, can be maximized by tailoring the optical constants of the metal and dielectric. In this review, we have described different types of solar absorber coatings with particular emphasis on dielectric-metal-dielectric (DMD) -based absorber coatings. We have presented a brief theoretical overview to comprehend physics of DMD coatings. This review additionally highlights some of the case studies based on the DMD -based absorber coatings with the high temperature stability and their importance in the context of CSP technologies.

The use of the back surface field BSF within the thin film cells isn't elaborated in a current state of research. In this article we try to adapt it to the Cu(In,Ga)Se2 thin film solar cells. The theoretical study is based on the resolution in one dimension of the equations which govern the behaviour of a photovoltaic cell. The spectrum used is the AM 1.5. The experimental method takes into account all physical phenomena which happen in the solar cell. The comparison of the macroscopic electric parameters of the two cells with BSF and without BSF enabled us to obtain a conversion efficiency of 21.95% for the cell with BSF whereas it is equal to 20.78% for the cell without BSF. The use of the BSF presents a broad maximum absorption band which extends from 0.4µm to 1µm through the study of the quantum efficiency of the cell. The spectral response of the layer reaches a value of 0.7A.W-1 for an incidental wavelength of approximately 1000nm which corresponds to the gap of the absorber of the solar cell of 1.2eV. The improvement of the thickness of the p+ CIGS up-doped, indicates an optimal thickness of 0.5.µm. We find for this thickness an open circuit voltage of 0.71V, a short-circuit current density of 37.409mA.cm-2 and a conversion efficiency of 21.95%. The optimization of the doping concentration acceptors of the p+ CIGS, shows that the optimal concentration corresponds to 10E18cm-3. We find with this acceptors density an open circuit voltage of 0.69V, a short circuit current density of 37.40mA.cm-2 and a conversion efficiency of 21.74%.

As a high potential renewable power source, solar energy is becoming one of the most important energies of the future. Recently, there has been an enormous increase in the understanding of the operational principle of photovoltaic devices, which has led to a rapid increase in the power conversion efficiencies of such devices. Solar cells vary under temperature changes; the change in temperature will affect the power output from the cells. This paper discusses the effect of light intensity and temperature on the performance parameters of monocrystalline and polycrystalline silicon solar devices. In this paper, the performance and overview use of solar cells is expressed. The role of temperature on the electric parameters of solar cells has been studied. The experimental results show that all electrical parameters of the solar cells, such as maximum output power, open circuit voltage, short circuit current, and fill factor, have changed with temperature variation. Solar cell performance decreases with increasing temperature, fundamentally owing to increased internal carrier recombination rates caused by increased carrier concentrations. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a photovoltaic (PV) module depend linearly upon the operating temperature. Solar cells vary under temperature changes; the change in temperature will affect the power output from the cells.

In this work, the effect of circular nanocavity on light trapping in a c-Si solar cell was studied by finite difference time domain (FDTD) simulation. The structure of the solar cell was considered to be Si3N4/c-Si/Ag, where the Ag layer was pattered and conformal growth of Si and Si3N4 was considered. The absorption spectra in the thin Si layer were determined and found 40 times higher at the infrared region (beyond 800 nm). For qualitative analysis, the short-circuit current of the solar cell was determined computationally by AM 1.5G solar illumination and found to be 2.1 times higher in the case of nanocavity as that compared to un-patterned solar cell. The enhancement in absorption in the solar cell is attributed to the different plasmonic modes coupled in the thin c-Si layer. The incident angle-dependent study was performed to observe the effect on enhancement in wide-angle incidence. The thickness-dependent study confirms 2.1 to 1.75 times enhancement in short-circuit current in 100- to 250-nm-thick c-Si layer. Therefore, this observation suggests that this structure has good prospect in achieving high conversion efficiency while reducing the device cost.

A spatially resolved absolute electroluminescence (EL) imaging method was utilized to analyze the photovoltaic properties and resistive loss properties of a GaAs thin-film solar cell. The I–V relation was extrapolated from the absolute EL efficiency measurements in conjunction with the external-quantum-efficiency (EQE) measurements; the EL extrapolated I–V relation has a merit over the conventional I–V relation measured with a solar simulator that it could eliminate the series resistance effect caused by external probe contact. Then, the mapping of the internal voltage of the solar cell and the sheet resistance of the window layer of the solar cell were obtained from the calibrated absolute EL imaging method. Finally, optic electroconversion losses of the solar cell including radiative loss, nonradiative loss, thermalization loss, transmission loss, and junction loss were quantified given by the EL and EQE measurements.

Could transparent solar cells work as the invisible power generator? Is it possible, in order to satisfy the on-site energy production, to install the transparent solar cell into the window of buildings and vehicles without recognizing the existence of energy harvesting entities? Here we propose and demonstrate the wide energy bandgap materials for visible light transmittance and UV photon absorption for power generation. All-transparent solar cell was achieved by the heterojunction of metal oxide layers. By using the solid-state sputtering method, transparent heterojunction (p-type NiO/n-type ZnO) was realized. A unit cell gave the record-high conversion efficiency of 6% with the enormous current density (2.7 mA/cm 2 ) and open circuit voltage of 532 mV. The remarkable transparent solar power is mainly attributed to the absolute UV absorption to induce the substantial excitonic effect for ZnO/NiO heterojunction. For integration, the transparent solar cell units were fabricated on a glass substrate to demonstrate the module of unit solar cells. Using the 3 × 3 unit cell solar module, a significant output voltage (> 2 V) was achieved to confirm the excellent connection manipulation of transparent solar cell units. By putting the transparent solar cells on buildings and vehicles, the electric power is spontaneously supplied from the Sun power but human eyes have no visible scarification. Transparent solar cells would provide a route for on-site energy generation.

Recent development in band-gap engineering technology has lead researches in the field of tandem photovoltaic solar cells to examine the feasibility of low-dimensional multi-junction solar cell. This is achieved by the combination of only two materials with different band-gaps, piled vertically with different thicknesses. It is theoretically possible to tailor a set of effective band-gaps responding to the requirement of tandem solar cells with a maximum efficiency. In the present work we investigate the potential of tandem solar cells based on GaPAs/GaInAs multiple quantum well structure. Efficiency limit has been previously calculated using the detailed balance principle for multi-junction solar cells. Adjusting the number of wells and their widths and barrier depth gives the possibility of varying the effective band-gap. Numerical resolution of Schrodinger equation for GaPAs/GaInAs multiple quantum well demonstrates the potential of this III–V compound to achieve a wide range of effective band-gaps varying from 2.27 to 0.70 eV. However, this material could be used to manufacture low-dimensional tandem solar cells and can achieve tandem solar cells up to six sub-cells, that can yield an efficiency limit up to 59% for series constrained AM 1.5 global radiation.

Although hybrid solar cells take advantages of both inorganic and organic semiconductors for high performance, there have not been comparably photoelectric conversion efficiencies as expected from this kind of solar cells till now. The photoelectric response behavior of inorganic/organic hybrid solar cells has been explained on the theory of inorganic solar cells, but the distinctive wavelength dependent photoelectric character of organic semiconductors has not been well considered. In this work, Ag2S/organic bulk heterojunction solar cell devices were designed and fabricated in-situ on indium tin oxide (ITO) based on the direct metal surface elemental reaction (DMSER) method, to understand the corresponding photoinduced charge carrier dynamics under different wavelength light. The commonly used small molecule Spiro-OMeTAD and polymeric PTB7-Th were selected as the organic components of the fabricated solar cells. In Ag2S/Spiro-OMeTAD, Ag2S donated the charge carriers and controlled the photoinduced charge carrier dynamics of the devices at both 355 nm and 532 nm lights. Under 532 nm light, the PTB7-Th acted as hole transport materials (HTM) rather than charge carrier donor. These results indicated that hybrid thin films without wavelength dependent charge carrier dynamics is preferred for high performance solar cells.

Highly luminescent CsPbBr3 perovskite quantum dots (QDs) have gained huge attention in research due to their various applications in optoelectronics, including as a light absorber in photovoltaic solar cells. To improve the performances of such devices, it requires a deeper knowledge on the charge transport dynamics inside the solar cell, which are related to its power-conversion efficiency. Here, we report the successful fabrication of an all-inorganic CsPbBr3 perovskite QD sensitized solar cell and the imaging of anomalous electrical potential distribution across the layers of the cell under different illuminations using Kelvin probe force microscopy. Carrier generation, separation, and transport capacity inside the cells are dependent on the light illumination. Large differences in surface potential between electron and hole transport layers with unbalanced carrier separation at the junction have been observed under white light (full solar spectrum) illumination. However, under monochromatic light (sin...

The effect of quantum confinement potential on the performance of a silicon-based heterojunction solar cell with an intrinsic thin-layer of a-Si:H is studied using numerical simulations. The presence of defects at c-Si/a-Si:H interface is studied quantitatively and, an analytical solution is investigated to interpret experimental results. Moreover, the impact of defect density at c-Si/a-Si:H interface on the solar cell operation is explained. By the use of a theoretical model, the effect of intrinsic amorphous layer thickness, and interface defect density on quasi-Fermi level are studied and the mechanisms of open circuit voltage (V oc ) variations, are interpreted successfully. It is shown that the best performance of heterojunction silicon solar cell with a single passivation layer is obtained when the thickness of (i)a-Si:H is 3–9 nm and heterojunction interface defect density is lower than 1010 cm−2 eV−1.

A highly efficient (>40%) ARC less dual junction solar cell is designed with low band gap GaSb. Use of GaSb as the bottom cell increases the spectral response of the cell up to 1800 nm. The simulation is performed by using Silvaco ATLAS device simulator under 1 and 1000 sun respectively. A detail discussion on obtained results like electric field generated, potential developed, photon’s generated in each layer, quantum efficiency and spectral response of the cell are provided in the result and discussion section. Other important parameters of the cell like open circuit voltage, short circuit current density, fill factor and efficiency are compared with previously reported results. This model shows an enhancement of 7.9% in its performance as compared to other reports.

There is increasing evidence that the presence of mobile ions in perovskite solar cells can cause a current-voltage curve hysteresis. However, it is still subject of ongoing debates how exactly mobile ions influence the device operation. We use drift-diffusion simulations incorporating mobile ions to describe IV-curves of preconditioned methylammonium lead iodide perovskite solar cells and compare them with experimental results. Our simulation results show that the hysteresis depends on the extent of surface recombination and on the diffusion length of charge carriers. We provide a detailed explanation for the reduced hysteresis of perovskite solar cells with high power conversion efficiencies. We find that in high-efficiency solar cells ion migration is still present, but does not cause a hysteresis effect. In these devices charge extraction is mainly driven by diffusion of free electrons and holes.

Small signal analysis for Al/ZnO/c-Si/Ag heterojunction solar cell structure is investigated in this simulation work. Effect of signal frequency, device temperature and junction interface defect state density on the junction diffusion capacitance and device conductance are thoroughly examined. Built in potential measurement highlights variation from 0.8 to 2.1 eV for the range100 Hz to 8 MHz which showing a good agreement with the practical value. Low temperature (10–100 K) conductance measurement at 2 V biasing results a localised Fermi level state density 9.54 × 1040 cm−3eV−1and evidences variable range hopping conduction. Excellent improvement of short circuit current density and efficiency is observed using MgxZn1-xO window layer. The increase in short circuit current density and efficiency due to the use of the window layer are 31.85 mA cm−2 and 19.17% respectively. For all the study illumination of 400 nm monochromatic light with photon flux 2.8 × 1017 cm−2s−1 and spectral width 10 nm are applied. Uses of 400 nm light is due to study of temperature dependency on open circuit voltage of solar cell. Using 1000 wt/m2 the efficiency of solar cell is enhanced from 19.88% to 23.15%.

We numerically study and analyze the light absorption enhancement in thin crystalline silicon solar cell with dual interface gratings. The structure combines the front dielectric nanowalls and the sinusoidal plasmonic grating at back reflector. We show that having specific interfaces with well-chosen period, fill factor and height can allow more efficient dielectric and plasmonic modes coupling into active layer and can improve the solar cell performance. For 1 µm active layer case, the optimal result for the proposed structure achieves short-circuit current of ~23.6 mA/cm 2 , which performs over 50% better than flat solar cell structure, the short-circuit current of which is ~15.5 mA/cm 2 . In addition, the active layer thickness and angular analysis show that the proposed structure maintains its advantage over flat structure.

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.

Sensitizer loading level is one of the key factors determined the performance of sensitized solar cells. In this work, we systemically studied the influence of photo-anode thicknesses on the performance of the quantum-dot sensitized solar cells. It is found that the photo-to-current conversion efficiency enhances with increased film thickness and peaks at around 20 μm. The optimal value is about twice as large as the dye counterparts. Here, we also uncover the underlying mechanism about the influence of film thickness over the photovoltaic performance of QDSSCs from the light harvesting and charge recombination viewpoint.

There are great improvements in III-V semiconductor solar cells including GaAs single junction solar cell and tandem solar cells in last decades. The common commercially used triple-junction solar cell mostly utilize a Ge bottom cell with an (In)GaAs and InGaP middle and top cell respectively. The (In)GaAs middle cell absorbs limited solar spectrum and show minimum short-circuit current in multiple junction solar cell, which determine the overall current of the cell. Theoretically, higher energy conversion efficiency will be obtained when introducea subcell with 1.0 eV band gap in series to the InGaP/GaAs/Ge tandem structures. Lattice-matched GaInNAs and lattice-mismatched In0.3Ga0.7As are two common choices for achieving 1.0 eV band gap. However, the addition of N to GaAs has detrimental effects on the material quality, limiting its utility to approaches that required photocurrent. And the lattice mismatch makes thick In0.3Ga0.7As heterogeneous epitaxial difficult. The incorporation of low band gap nanoscale materials, such as quantum well and quantum dots, into current limiting junction of a multijunction solar cell can tuning the effective bandgap and enhance the low-energy photon absorption, thereby increasing the short-circuit current. The samples are grown by solid-source molecular beam epitaxy (V80H) on p-GaAs (001) substrates using an As4 source. Sample A is a standard GaAs solar cell with PIN structure. Sample B contains 10 period 8 nm In0.15Ga0.85As QW and sample C contains 10 period InAs dots-in-well structure. The intrinsic region of these samples was at the same length of 630 nm to obtain the same build-in electric field. Besides the instinct region, the three samples are designed the same. The ohmic contact layer’s doping concentration is N D/ N A=3×1018 cm−3 and its thickness is 300 nm. The emitter doping concentration is N D=5×1017 cm−3 and its thickness is 150 nm; The base doping concentration is N A=5×1017 cm−3 and its thickness is 300 nm. The As4 pressure and the InAs QDs growth rate are 1×10−5 Torr and 0.1 ML/s, respectively. The XRD pattern of sample B (QWSC) shows clearly defined and intense satellite peaks indicating steep interface and periodicity quantum well. However, the XRD pattern of sample C (the InAs dots in well solar cell) shows blurring diffraction peaks which means increased interface roughness. Uniform QD structure with density of 2×1010 cm−2 can be observed in SEM. From the STEM, we can see well-defined unrelated pyramidal quantum dots separated by a nominal 50 nm GaAs spacing. From the contrast, the pyramid InAs QDs are estimated to have the lateral dimension of 27 nm and the height of 12 nm. The PC response of sample A rise at 600 nm and fall off at 870 nm, which is corresponding to the GaAs bandgap according to the PL peak position; the PC response of QWSC (sample B) rise at 600 nm and fall off at 990 nm, which is corresponding to the In0.15Ga0.85As bandgap in PL spectrum. The incorporation of In0.15Ga0.85As quantum wells in GaAs standard solar extend the absorption of solar spectrum from 900 nm to 1000 nm. The wavelength region from 700 nm to 900 nm in PC of QWSC is weaker than the GaAs standard solar cell. The insertion of InAs QDs into QWSC can extend the infrared photon absorption to the wavelength of 1300 nm. The insertion of InAs quantum dots into In0.15Ga0.85As/GaAs quantum well solar cell extend the absorption of infrared light and the J sc reaches 13.68 mA/cm2, giving a 37.8% increase in short-circuit current over the baseline solar cell current. Because the voltage of multiple junction solar cell is the sum of the sub cell’s voltage. The voltage decreasement with the insertion of InAs quantum dots do not influence the overall voltage of multiple junction solar cell. In summary, the incorporation of quantum well and quantum dots in GaAs solar cell result in extended solar spectrum absorption and contribute to the sub-band gap current gains for GaAs solar cell. Especially, InAs dots-in-well solar cell can extend the absorption spectrum to the wavelength of 1300 nm, and increase by 37.8% in short-circuit current, which shows great potential in mitigating current mismatch of multiple junction solar cell. Furthermore, designing new multiple junction solar cell becomes possible.

In this paper a novel solar cell based on MEMS technology has been proposed. The process of converting solar energy to electrical energy has been done using MEMS solar cell which is able to convert heat to voltage with temperature variation and direct piezoelectric effect. First, a bimaterial cantilever (with Al and SiO2 materials) is deflected by absorbing solar energy and thus solar energy is converted to mechanical energy. Then the produced mechanical vibration is converted to electrical energy using a piezoelectric layer of aluminum nitride. Compared with conventional solar cells, this structure is able to absorb whole solar radiation spectrum, the produced electrical voltage is AC with 0.75 V amplitude, therefore no need inverters and the size of our MEMS solar cell (400 µm2) is smaller than the previous works.

Photonic nanostructures are now widely investigated as light trapping textures to achieve significant absorption in thin film solar cells. In this paper, we quickly designed a high efficiency photonic structure for thin film silicon solar cells. Based on the coupled mode theory, we compared classic lattice photonic structures and demonstrated triangular lattice structure exhibits better light trapping performance. Through analysis of short circuit current density, unit cells with heart-pentagon polygon arrangement were verified to offer superior absorption in entire silicon absorption spectrum. Finally, the comparisons with other reported textures validated our design.

Replacing the present-day commercial single junction silicon (Si) solar cells with low cost, high efficiency solar cells is imperative, in order to compete with other existing energy technologies. Many research groups have looked into using III–V materials, tandem junction solar cells and thin-film technologies to reach higher efficiencies. However, many of these techniques involve expensive materials or costly manufacturing processes. In this research, we focus on a tandem junction solar cell design that is based on a thin-film perovskite top cell and wafer-based Si bottom cell. In order to analyze the performance of the tandem cell, an analytical model is needed to compute the quantum efficiency and characteristic solar cell data. The highly versatile Matlab-based analytical model presented in this work is capable of modeling different kinds of tandem cells based on a variety of solar absorber combinations. The model allows user to adjust input parameters, such as reflectivity, material thickness, donor and acceptor densities, and carrier lifetimes in order to optimize the quantum efficiency, maximum power output, open circuit voltage, and short circuit current quantities of the cell. Using this analytical model, we were able to design a perovskite and black Silicon (bSi) tandem cell, which reached an efficiency of greater than 30%.

Amorphous silicon thin film solar cells exhibit a degrading effect during the first hours of illumination. This phenomenon is worsen by thick intrinsic layers, thus light trapping strategies are employed to increase optical absorption. We use a method developed to measure the performance of these techniques. The procedure allows us to approximate both, the effective path of light inside the cell and the collection length of carriers, out of the internal quantum efficiency. Simulated and experimental data were compared finding good agreement.

Improvement of solar cell efficiency beyond the Shockley–Queisser limit requires introduction of new physical concepts. One such concept is hot carrier solar cell, proposed more than three decades ago and still not impressively demonstrated in experiment. Here we show that hot carrier solar cell may be considered as thermoelectric device based on Seebeck effect. This enables one to describe the operation of hot carrier solar cell in a simple way. We fabricated a prototype of the hot carrier solar cell showing open circuit voltage at room temperature larger than the band gap in the absorber material. Extrapolation of open circuit voltage to absolute zero temperature results in barrier height depending on light intensity, interpreted by splitting of quasi-Fermi levels between the regions of different carrier temperature. Properties of the prototype solar cell may be described by kinetic transport theory as well as from the point of view of the thermoelectric theory.

In this work we report the characterization of perovskite solar cells with mesoscopic TiO2/Al2O3/NiO/carbon architecture by analyzing the dependence of photovoltaic parameters on temperature and illumination intensity. This perovskite device shows impressive power conversion efficiency at room temperature (>14 %) and at low temperature of 80 K (>5 %). This enables unequivocal identification of the contribution of CH3NH3PbI3 to construction of the built-in electric field, and thus, the temperature dependent photovoltaic parameters. The typical feature of this type solar cell is that open-circuit voltage follows behaviour of the dielectric constant of CH3NH3PbI3. In addition, the dependence of current on light intensity shifts from the space-charge-limited to diffusion-limited mechanisms as increasing temperature. By using the observed significant short-circuit current density of 12.76 mA cm−2 at 80 K the exciton-binding energy of CH3NH3PbI3 is evaluated to be less 6.9 meV in an operating device, which can be further verified with Elliott's formula.

Herein, the open-circuit voltage (V[OC]) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of V[OC] in order to discuss the difference in the primary loss mechanism of V[OC] between them. As a result, the photon energy loss for polymer solar cells is in the range of 0.7–1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of V[OC] in both solar cells are further discussed on the basis of the experimental data.

InGaN has been predicted to be an efficient photovoltaic material. However, the high-density polarization charges and large potential barrier at the i-InGaN/n-GaN interface create an electric field that severely decreases the collection efficiency of p-InGaN/i-InGaN/n-GaN heterostructure solar cells. We demonstrate that, according to numerical simulations, utilizing a p-InGaN/i-InGaN/n-ZnO heterostructure can greatly reduce the piezoelectric field in the absorption layer and reduce the potential barrier between the n-type layer and the absorption layer interface, thus improving the performances of the solar cell. Moreover, we studied the influence of the band alignment on the ZnO/InGaN interface on the performance of the solar cell. We found that the band alignment of the ZnO/InGaN interface can keep the solar cells at a very high efficiency over a wide scope.

A record-high efficiency of 16.92% was realized by using microscale-patterned Si solar cells. Si microwire (SiMW) solar cells were designed to compare their performances with the standard flat-Si solar cell. The diameter and period of SiMWs were tuned to investigate the effects on the operation and the electrical properties of the solar cells. The highest efficiency SiMW solar cell has a width of 1.57 µm to provide the significantly enhanced efficiency of 16.92% from 10.15% of the flat-Si solar cell, due to the improved values of open circuit voltage (608 mV), short circuit current density (36.47 mA/cm 2 ) and fill factor (76.29%). Impedance spectroscopy and capacitance-voltage studies were carried out to obtain series and shunt resistances, built-in potential, acceptor carrier density, depletion width and flat band potential. Optical properties of SiMW solar cells were analyzed by external and internal quantum efficiencies. The carrier lifetime was measured by using open circuit voltage decay technique. Systematic analyses were performed to reveal the optical and electrical features of SiMW solar cells. These findings may provide efficient design schemes for high-performing solar cells using structured platforms.

The irradiance concentrated along the edges of a planar luminescent solar concentrator (LSC) is not uniform across their length. This geometrical effect results in a deviation of up to 40% between the extreme ends and the middle of an edge for a large-area LSC. Consequently, the typically in-series interconnected solar cells attached to the edges of the LSC are not illuminated equally resulting to current mismatch. It is shown that by reducing the lengths of the more central solar cells so that current matching is achieved, more cells can be attached to each edge. This way, the voltage and power output of the string can be increased. In this work, a 60 cm × 60 cm × 0.3 cm LSC with 26 solar cells mounted to its edges was constructed and characterized. These dimensions result in geometrical concentration of 50×, while the LSC exhibited average irradiance concentration of 4.8×. An increase of 15% in power output and efficiency is demonstrated via the reduction of the length of central cells, current matching, and the consequent connection of one more cell to the string of an edge. A solar-to-electric power conversion efficiency of 1.55% is reported for the large-area LSC module.

Absorption of amorphous-Si hydrogenated (aSi-H) solar cells can be enhanced by using dielectric nanostructures made of Si3N4 that work like antireflection coatings. The analysis focus on the short-circuit current delivered by the cell under solar irradiance, and it is made taking into account every layer and structure of an aSi-H cell. A customized design of the antireflection coating in the form of nanostructured dielectric layers, produces a short-circuit current enhancement of 15.2% with respect to the reference flat solar cell, and a lower reflectivity of the cell. Three different geometries of linear nanostructures have been analyzed and compared with quite similar results among them. An improvement in performance has been also obtained for realizable geometrical dimensions that could be fabricated while maintaining electric conductivity of the front contact.

Trap-assisted recombination, despite being lower as compared with traditional inorganic solar cells, is still the dominant recombination mechanism in perovskite solar cells (PSCs) and limits their efficiency. We investigate the attributes of the primary trap assisted recombination channels (grain boundaries and interfaces) and their correlation to defect ions in PSCs. We achieve this by using a validated device model to fit the simulations to the experimental data of efficient vacuum-deposited p-i-n and n-i-p CH3NH3PbI3 solar cells, including the light intensity dependence of the open circuit voltage and fill factor. We find that, despite the presence of traps at interfaces and grain boundaries (GBs), their neutral (when filled with photogenerated charges) disposition along with the long-lived nature of holes leads to the high performance of PSCs. The sign of the traps (when filled) is of little importance in efficient solar cells with compact morphologies (fused GBs, low trap density). On the other hand, solar cells with noncompact morphologies (open GBs, high trap density) are sensitive to the sign of the traps and hence to the cell preparation methods. Even in the presence of traps at GBs, trap-assisted recombination at interfaces (between the transport layers and the perovskite) is the dominant loss mechanism. We find a direct correlation between the density of traps, the density of mobile ionic defects, and the degree of hysteresis observed in the current voltage (J-V) characteristics. The presence of defect states or mobile ions not only limits the device performance but also plays a role in the J-V hysteresis.

In this paper, we have analyzed the antireflection, diffraction order, distribution of light field energy density and the photoelectric conversion efficiency of thin film solar cell with the silicon square nanoconical hole (SiSNH) decorated on its surface under different polarization modes and different top diameters (Dtop). The results show that when the incident azimuthal angle (φ) of the transverse electric (TE) polarization takes the value of 30°, an ultimate efficiency of thin film solar cells with optimized SiSNH array is up to 42.83%, which is 3.09 times of the 2.33 μm thick film solar cell. The results also show that the enhanced ultimate efficiency of the thin film solar cell with SiSNH array is insensitive to Dtop and incident light zenith (θ) angle.

The heating of a solar cell has significant adverse consequences on both its efficiency and its reliability. Here to fully exploit the cooling potential of solar cells, we experimentally characterized the thermal radiation and solar absorption properties of current silicon solar cells and, on the basis of such experimental characterization, propose a comprehensive photonic approach by simultaneously performing radiative cooling while also selectively utilizing sunlight. In particular, we design a photonic cooler made of one-dimensional photonic films that can strongly radiate heat through its thermal emission while also significantly reflecting the solar spectrum in the sub-band-gap and ultraviolet regimes. We show that applying this photonic cooler to a solar panel can lower the cell temperature by over 5.7 °C. We also show that this photonic cooler can be used in a concentrated photovoltaic system to significantly reduce the solar cell temperature or required cooling power. This photonic cooler can be r...

In recent years, the development of quantum well solar cells QWSCs (Quantum Well Solar Cells) has generated a great deal of interest. These configurations have shown good promise to optimize the low conversion efficiency of conventional solar cells because of the high rate of absorption losses present in them. In this work, we are interested in modeling and simulation of two different structures of solar cells, a simple solar cell based on silicon Si and a quantum well solar cell SiGe/Si. When a solar cell is compared to 80 quantum well layers of Si 0.8 Ge 0.2 with a pin solar cell based on Si. The short circuit current J sc increases from 23.55 to 37.48 mA/cm 2 with a relative increase of 59.15% found. In addition, the limit of the absorption band of the lower energy photons extends from 1100 nm to 2000 nm.

This paper presents a possible solution to improve the efficiency of photovoltaic solar cells. An external electric field is applied on a silicon photovoltaic solar cell, inducing band-trap ionization of charge carriers. Output current is then monitored and the thermodynamic efficiency is calculated. Results show on the one hand a significant increase in efficiency for a certain margin of applied electric field, and on the another hand the instabilities of efficiency. A simple approach is then suggested for the implementation of these results. An efficiency of 67% has been reached for an applied electric of 1586 V/Cm.

The characterization and modeling of silicon solar cells under nonstandard conditions is an essential task in order to predict and optimize the annual yield when installed in the field. In this paper, focus is set on the temperature dependence of fundamental physical models for numerical device simulation of silicon solar cells. A wide range of industrially relevant solar cell concepts is simulated and compared to experimental data. The influence of fundamental physical models on the temperature dependence of the simulated devices is investigated. It is found that our simulations are in good agreement with experimental results for silicon solar cells that are limited by extrinsic defect or surface recombination. This is not the case for solar cells featuring carrier-selective contacts where intrinsic recombination processes, such as Auger recombination and radiative recombination, have a significant influence.

In this work, the performance of solar cell based on CdS-n/Cu 2 ZnSnS 4 -p hetero-junction is numerically simulated. The aim of the study is to investigate the influence of thickness, defects density and bandgap energy of absorber layer CZTS and the thickness of the buffer layer CdS of the solar cell on electrical parameters J sc , V oc , FF and efficiency η of the cell. The results of our simulation allowed us to optimize the parameters above mentioned in order to get the best efficiency at the optimal band gap which corresponds to the maximum of the solar spectrum with optimal values of the electrical performances of the cell. This results lead to develop CZTS solar cells with high efficiency and low cost and give a help full indication for fabrication process.

In this paper, the effects of random Ag nanoparticle used within the active layer of Si based thin film solar cell are investigated. To avoid the complexity of taking into account all random nanoparticles, an effective dielectric function for random Ag nanoparticles and Si nanocomposites is used that is the Maxwell–Garnet theory along with Percus–Yevick correction term. Considering the energy reservation law and using the effective dielectric function, the absorbance of the active layer, therefore, the solar cell's maximum short current density is obtained. Also, the maximum external quantum efficiency of the solar cell is obtained using the optimum values for the radius and filling fraction of Ag nanoparticles.

Summary A novel multi-junction GaP/InP/Si solar cells with improved p++AlGaAs/n++ AlGaAs tunnel junction model is designed using the Synopsys/RSoft/Solar cell utility software. The optical and electrical simulations of this cell are performed using the 2D full-wave and solar cell utility, resulting in an open circuit voltage of 3.02 V, short circuit current density of 15.942 mA/cm2, fill factor of 82.7%, and power conversion efficiency of 44.23%. Then, an optimization study of a function of variation in thickness of different layers is performed. Simulation results of the optimized structure under AM 1.5G condition showed a small improvement in the short circuit current density by 0.38%, efficiency by 0.375%, whereas the fill factor and open circuit voltage are maintained the same. The proposed multi-junction solar cell has reported the highest power conversion efficiency of 44.397% among the III–V triple junction solar cells designed already. Copyright © 2017 John Wiley & Sons, Ltd.