Maximum Solar Cell Efficiency Research Articles

Modeling of Photovoltaic Characteristics of a TiO<sub>2</sub>/Porous-Si/Si-Based Heterojunction Solar Cell

This work is focused on the study of photosensitive structures based on porous Si and film TiO2, which are promising for solar energy. For numerical simulation of the transportation and accumulation of charge carriers in the considered heterostructure, the drift-diffusion approximation of the semiclassical approach was proposed. A device scheme of a solar cell model based on TiO2/porous-Si/Si heterostructures is proposed. Production of photoconverters of solar cells based on the TiO2/porous-Si/Si heterostructure can be carried out according to the standard method supplemented by additional technological operations. Ohmic contacts are formed in the upper and lower parts of the structure above the TiO2 and Si layers. The strip system of contacts is a contact grid, with hatching, the surface coefficient should not exceed 5%. The thickness of the applied layer of photoresist should be 1 μm. Using the PC1D program, the light characteristics of the fabricated structure were calculated (open circuit voltage VOC, short circuit current ISC, fill factor FF and efficiency η), and current-voltage characteristics were plotted. The influence of the thickness and doping level Nd and Na of porous Si and TiO2 layers on the productivity of a heterojunction solar cell TiO2/porous-Si/Si was studied in order to obtain a device with a good conversion efficiency. It was found that the energy conversion efficiency of a TiO2/porous-Si/Si solar cell can reach 22.5 %. Based on the optimized simulation conditions, it was found that the maximum solar cell efficiency is achieved at thicknesses of 100 and 200 nm and donor concentration of Nd=1∙1017 cm-3 and acceptor concentration of Na=1∙1018 cm-3 for TiO2 and porous Si buffer layer, accordingly.

Elucidating the coherent and incoherent reflection of plane-waves in finite thickness media: a practical pedagogical application

The propagation of light through a thin film interfaced between two semi-infinite media serves as a compelling illustration for elucidating electromagnetic wave interactions with matter at the undergraduate level. Despite its pedagogical significance and diverse technological applications, this model often receives inadequate attention in foundational electromagnetism literature, limiting early student exposure to this emblematic concept. In this pedagogical initiative, we present a comprehensive analysis of electromagnetic wave propagation through a dielectric medium positioned between semi-infinite media. We examine interference phenomena arising from back-and-forth reflected waves within the dielectric, focusing on the coherent and incoherent reflection regimes as limiting cases. Employing rigorous analytical treatment, we delineate transmittance and reflectance profiles, offering students a lucid understanding of how the refractive index’s real and imaginary components compete and manifest under specific conditions. This analytical approach enhances students’ comprehension of electromagnetic wave behavior within diverse mediums. Furthermore, we extend this theoretical foundation to practical applications, emphasizing renewable energy contexts. By calculating absorptance, we estimate the maximum photo-generated current and power conversion efficiency of a prototype solar cell, establishing a tangible link between theoretical knowledge and real-world solar energy utilization.

Numerical simulation of Cu2Te based thin film solar cell with Cu2O HTL for high efficiency

Copper telluride (Cu2Te) is an attractive semiconductor absorber material for thin film solar cells due to its excellent opto-electronic properties. However, the maximum experimental conversion efficiency of the Cu2Te thin film solar cell remains at about 6%. In the present study, the cuprous oxide (Cu2O) material as the hole transport layer (HTL) has been proposed in the Cu2Te based thin film solar cell. The purpose of this work is to enhance the device performance by inserting widely available Cu2O material as HTL into the basic heterojunction structure. The effects of several material parameters such as thickness, carrier concentration, defect density and back contact metal work function on the device performance of the proposed Cu2Te thin film solar cell consisting of FTO/WS2/Cu2Te/Cu2O/metal have been studied and numerical investigated using the wxAMPS program. Optimized conversion efficiency of the proposed Cu2Te thin film solar cell with Au as back contact metal has been obtained to be 30.32%. These results reveal that the Cu2O material as HTL can be employed to fabricate low cost and highly efficient Cu2Te thin film solar cells.

Establishment of Justified Parameter Optimization Sequence for obtaining Maximum Solar Cell Efficiency

This paper questions the validity of t-NA/D-Nt technique for solar cell optimization and establishes the scientifically and experimentally-justified NA/D-Nt-t parameter optimization sequence for the same. Fundamental mathematical formulations considering numerous physical perspectives are presented for scientific justification of newly proposed optimization procedure. This is followed by an in-depth comprehensive analysis on sequence of parameter optimization applied in numerous widely-implemented solar cell fabrication techniques. It is found that, in each fabrication technique, the same optimization sequence of NA/D-Nt-t is implemented. Along with this, simulation study of sample solar cell is presented for further analysis of our conceptualization. It is identified that the time at which initial values of NA/D and Nt are replaced by the optimized ones to convert the initial solar cell to an optimized one, the value of absorber thickness at which solar cell produces maximum yield also changes. It was observed that NA/D-Nt-t optimization sequence increased device efficiency from 6.97% to 17.05% (144.6% increment) as compared to 55.8% increment from 6.97% to 10.86% in case of conventional t-NA/D-Nt optimization sequence. Moreover, only the NA/D-Nt-t approach produced EQE graph that matches with the experimentally-observed EQE curves of device. Hence, the newly proposed scientifically and experimentally-justified NA/D-Nt-t optimization sequence proposed for first time in this paper, truly optimizes solar cell device so that it offers maximum-possible efficiency reliably.

Numerical Simulation Study of CIGS-based Thin Film and Heterojunction Solar Cells: Doping and Buffer/Absorber Layer Optimization for Maximum Efficiency

In this work we present the results of the numerical simulation study of the electrical characteristics of a CIGS-based thin film and heterojunction solar cell and their interpretations. First, we will simulate two solar cells of structures: ZnO/CdS(n)/CIGS(p)/Mo and ZnO/ZnS(n)/CIGS(p)/Mo using the SCAPS-1D software. We will compare the results of the electrical simulation of the CdS cell with those found experimentally. Next, we will compare the electrical simulation results of the CdS cell with the ZnS cell. After that, we will choose the best cell to study the effect of doping and buffer/absorber layer thickness on the photovoltaic parameters () of the solar cell with the aim of achieving maximum efficiency of the CIGS-based solar cell.

(Invited, Digital Presentation) Photovoltaic Applications Using Energy Transfer Characteristics from Quantum Dots

Silicon-related materials are most commonly used in solar cells and become now an invaluable material. However, a reported maximum energy conversion efficiency of Si solar cell is close to reaching its theoretical limits. To further improve the cell performance and create new functions, it will become increasingly important to functionalize Si materials using nanostructures. One- and zero-dimensional Si nanostructures called Si nanowires (SiNWs) and Si quantum dots (Si QDs) are increasingly being used as new solar cell materials. Our group has shown that the conversion efficiency of solar cells can be increased by the non-radiation energy transfer (NRET) from Si QDs [1]. Recently, research has been developed on compound semiconductor QDs and perovskite QDs, and the conversion efficiency has been successfully increased [3-7].n-type SiNW arrays were fabricated by electroless etching and Bosch & nanoimprint lithography followed by CVD process. The CVD process was performed to form p-type Si layer for pn homojunction. Hybrid heterojunction cells of PEDOT:PSS and n-SiNWs were also fabricated. Passivation by ozone and hydrogen were applied to improve the solar cell properties [2]. After the cell fabrications, the solar cells were coated with Si QDs, CdZnS/ZnS QDs, CdZnSe/ZnS QDs and perovskite QDs. The fabrication methods and conditions of QDs have been reported elsewhere [1-7]Energy transfer effects such as NRET are new ways of increasing solar cell efficiency. To effectively use the NRET effect, the surface of Si QDs should be fully passivated by ligand molecules. The NRET process is a highly distance-dependent phenomenon, and its dependence on the length of the passivation ligands clearly showed this. NRET efficiency was increased by shortening the ligand length from 1-octadecene to 1-octene, resulting in higher JSC, ultimately providing higher energy conversion efficiency. The efficiency was increased about 1-2 % by adding SiQDs. We also observed the same effect for CdZnS/ZnS QDs, CdZnSe/ZnS QDs and perovskite CsPbCl3 QDs. In these cases, in addition to the NRET effect, the radiative energy transfer (RET) effect also contributes to the increase in conversion efficiency.

Photonic crystals for highly efficient silicon single junction solar cells

The maximum achievable silicon single junction solar cell efficiency is limited by intrinsic recombination and by its limited capability of absorbing sun light. For Lambertian light trapping the maximum theoretical solar cell efficiency is around 29.5%. Recently a new approach for light trapping has been proposed for silicon photovoltaics. Highly regular structures with a size in the range of the wavelengths of the incident light act as so-called photonic crystals. Such structures allow wave-interference light trapping beyond the Lambertian limit. Applying these photonic crystals to silicon solar cells can help to reduce the absorber thickness and thus to minimizing the unavoidable intrinsic recombination. From a simulation study, we can conclude that 31.6% is the maximum possible single junction solar cell efficiency for a 15 μm-thin substrate. Furthermore, we present a process flow for the preparation of regular inverted pyramid structure, that acts as photonic crystal. Finally, regular inverted pyramid structures are prepared on polished and shiny-etched, i. e. on surfaces with a certain roughness, substrates. Surface passivation of these structured surfaces shows as good lifetimes as on conventional randomly pyramid textured surface. Excellent total saturation current densities on asymmetric samples of 4 ± 2 fA/cm2 for n-type and of 4.5 ± 2.2 fA/cm2 on p-type substrates are obtained.

Ab initio calculation of the detailed balance limit to the photovoltaic efficiency of single p-n junction kesterite solar cells

The thermodynamic limit of photovoltaic efficiency for a single-junction solar cell can be readily predicted using the bandgap of the active light absorbing material. Such an approach overlooks the energy loss due to non-radiative electron-hole processes. We propose a practical ab initio procedure to determine the maximum efficiency of a thin-film solar cell that takes into account both radiative and non-radiative recombination. The required input includes the frequency-dependent optical absorption coefficient, as well as the capture cross sections and equilibrium populations of point defects. For kesterite-structured Cu2ZnSnS4, the radiative limit is reached for a film thickness of around 2.6 μm, where the efficiency gain due to light absorption is counterbalanced by losses due to the increase in recombination current.

Biotemplated Synthesis of Titanium Oxide Nanoparticles in the Presence of Root Extract of Kniphofia schemperi and Its Application for Dye Sensitized Solar Cells

Metal oxide nanoparticles prepared by biological route using green plant parts as a template are eco-friendly as well as yield good results than the conventional methods. This present study focusses on biosynthesis and characterization of TiO2 NPs using root extract of Kniphofia schemperi for dye-sensitized solar cells. TiO2 NPs were synthesized using 0.25 M titanium tetra butoxide in the presence of root extract of Kniphofia schemperi with the volume ratios. The analysis result revealed that the synthesized TiO2 NPs were thermally stable above 500°C and have spherical morphology, with the average crystalline size of 11.7, 8.3, and 8.6 nm, and band gap energy of 3.35 eV, 3.33 eV, and 3.36 eV, respectively, for the TiO2 NPs prepared at the volume ratios of 2 : 3, 1 : 1, and 3 : 2. Biosynthesized TiO2 NPs were used as photoanode in dye-sensitized solar cells (a device used for converting absorbed light into electricity). Solar cell devices were fabricated using roots of Kniphofia schemperi sensitizer in the presence of TiO2 NPs biosynthesized within (2 : 3, 1 : 1, and 3 : 2) volume ratio, which showed power conversion efficiency of 0.039%, 0.117%, and 1.3%. Incident photon to current conversion efficiency (IPCE) analysis using TiO2 (2 : 3, 1 : 1, and 3 : 2) photoelectrodes showed 6.64%, 2.66%, and 18%. Among the biosynthesized TiO2 different volume ratios, TiO2 (3 : 2) NPs showed relatively maximum solar cell efficiency and IPCE value due to its uniform spherical shape that enables to absorb large dye molecules on its surface, and this intern improves device efficiency.

Calculation of electronic and optical properties of methylammonium lead iodide perovskite for application in solar cell.

Organic-inorganic metal halide perovskite materials, i.e., ABX3 (A = methylammonium, B = Pb, X = Cl, Br, I) have been proved to be outstanding for solar energy conversion. They provide a solution to renewable energy problems with good efficiency and cost-effective technology. Here, we report the initial calculations done by solving Kohn-Sham equations by the use of density function theory. The electronic structural and band gap of CH3NH3PbI3 material are obtained by using different exchange-correlation potential (PBE, PBE-sol, GGA). Further, solar cell devices with CH3NH3PbI3 as absorption layer and CdS/TiO2/ZnTe as buffer layer have been modeled; device physics is discussed and performance of solar cell structure is analyzed in terms of short circuit current density, open circuit voltage, efficiency, fill factor, and quantum efficiency. The maximum efficiency of CH3NH3PbI3 solar cell is found to be 19.6% with TiO2 buffer layer, whereas efficiency with ZnTe buffer layer is also comparable which is 19.5%. Further the effect of layer thickness and temperature are analyzed for maximum efficiency.

Challenges in tin perovskite solar cells.

Perovskite solar cells are the rising star of third-generation photovoltaic technology. With a power conversion efficiency of 25.5%, the record efficiency is close to the theoretical maximum efficiency of a single-junction solar cell. However, lead toxicity threatens commercialization efforts and market accessibility. In this context, Sn-based perovskites are a safe alternative. Nevertheless, the efficiency of Sn-based devices falls far behind the efficiency of Pb-based counterparts. This concise review sheds light on the challenges that the field faces toward making Sn-based perovskites the perovskite photovoltaic benchmark. We identified four key challenges: materials and solvents, film formation, Sn(II) oxidation, and energy band alignment. We illustrate every single challenge and highlight the most successful attempts to overcome them. Finally, we provide our opinion on the most promising trends of this field in the future.

Thickness dependence of solar cell efficiency in transition metal dichalcogenides MX2 (M: Mo, W; X: S, Se, Te)

Bulk transition metal dichalcogenides are indirect gap semiconductors with optical gaps in the range of 0.7–1.6 eV, which makes them suitable for solar cell applications. In this work, we study the electronic structure, optical properties, and the thickness dependence of the solar cell efficiencies of MX2 (M: Mo, W; X: S, Se, Te) with density functional theory and GW + BSE. Through this analysis, we find a change in solar cell efficiency trends at slab thicknesses of 3 μm. For thin films solar cells (thicknesses smaller than 3 μm), the tellurides present the highest efficiencies (about 20% for a 100 nm thick slab). In contrast, for thicknesses greater than 3 μm, our results indicate that a maximum solar cell efficiency can be achieved in WS2. For instance, a 100 μm slab of WS2 presents a solar cell efficiency of 36.3%, making this material a promising candidate for solar cell applications.

With PBDB-T as the Donor, the PCE of Non-Fullerene Organic Solar Cells Based on Small Molecule INTIC Increased by 52.4.

At present, most high-performance non-fullerene materials are centered on fused rings. With the increase in the number of fused rings, production costs and production difficulties increase. Compared with other non-fullerenes, small molecule INTIC has the advantages of easy synthesis and strong and wide infrared absorption. According to our previous report, the maximum power conversion efficiency (PCE) of an organic solar cell using PTB7-Th:INTIC as the active layer was 7.27%. In this work, other polymers, PTB7, PBDB-T and PBDB-T-2F, as the donor materials, with INTIC as the acceptor, are selected to fabricate cells with the same structure to optimize their photovoltaic performance. The experimental results show that the optimal PCE of PBDB-T:INTIC based organic solar cells is 11.08%, which, thanks to the open voltage (VOC) increases from 0.80 V to 0.84 V, the short circuit current (JSC) increases from 15.32 mA/cm2 to 19.42 mA/cm2 and the fill factor (FF) increases from 60.08% to 67.89%, then a 52.4% improvement in PCE is the result, compared with the devices based on PTB7-Th:INTIC. This is because the PBDB-T:INTIC system has better carrier dissociation and extraction, carrier transportation and higher carrier mobility.

High-Efficiency Multiple Quantum Well Triple-Junction Tandem Solar Cell

This work shows the design of a high-efficiency solar cell in an indium-gallium-arsenide/–gallium-arsenide multiple quantum well (MQW) structure. The main concerns regarding the solar cell are its fabrication complexity, design complexity, and efficiency. Tandem solar cells are designed to absorb the maximum amount of solar energy. In a tandem structure, different positive-negative junctions are responsible for absorbing different portions of the solar spectrum. Besides this, the embedded MQW structure also helps to increase the efficiency of the solar cell. The maximum efficiency of the tandem solar cell in the different material structures is reported to be around 45%–46%. Proper matching of different material parameters such as the lattice-matched semiconductor and thickness of the tandem solar cell can increase the efficiency of the solar cell. This paper introduces a tandem solar cell having an efficiency of around 50%. This comparative study shows the improved performance of the proposed solar cell. A graphical user interface is also developed for solar cell simulation.

Reducing lead toxicity in the methylammonium lead halide MAPbI3 : Why Sn substitution should be preferred to Pb vacancy for optimum solar cell efficiency

Methylammonium lead halide $({\mathrm{MAPbI}}_{3})$ perovskite has emerged as one of the frontier optoelectronic semiconductors. To avoid lead toxicity, the role of Sn substitution and Pb vacancy (Pb-$\ensuremath{\boxtimes})$ are addressed in regulating stability and solar cell efficiency of ${\mathrm{MAPb}}_{1\ensuremath{-}X\ensuremath{-}Y}{\mathrm{Sn}}_{X}{\ensuremath{\boxtimes}}_{Y}{\mathrm{I}}_{3}$ perovskite using hybrid density functional theory (DFT). The role of spin-orbit coupling (SOC) and the electron's self-interaction error are examined carefully. We find to reduce the Pb content from pristine ${\mathrm{MAPbI}}_{3}$, Sn substitution has a more favorable thermodynamic stability than creating Pb-$\ensuremath{\boxtimes}$. Moreover, on substituting Sn, due to strong $s\text{\ensuremath{-}}p$ and $p\text{\ensuremath{-}}p$ couplings, the lower parts of the conduction band gets shifted downwards, which results in the reduction of the band gap (direct). This further helps us to get a high optical absorption coefficient (redshifted) and maximum solar cell efficiency in ${\mathrm{MAPb}}_{1\ensuremath{-}X}{\mathrm{Sn}}_{X}{\mathrm{I}}_{3}$ for $0<X\ensuremath{\le}0.5$.

Characteristics of Perovskite Solar Cell with Nano-Structured MoO3 Hole Transfer Layer Prepared by Hydrothermal Synthesis

MoO3 metal oxide nanostructure was formed by hydrothermal synthesis, and a perovskite solar cell with an MoO3 hole transfer layer was fabricated and evaluated. The characteristics of the MoO3 thin film were analyzed according to the change of hydrothermal synthesis temperature in the range of 100 ℃ to 200 ℃ and mass ratio of AMT : nitric acid of 1 : 3 ~ 15 wt%. The influence on the photoelectric conversion efficiency of the solar cell was evaluated. Nanorod-shaped MoO3 thin films were formed in the temperature range of 150 ℃ to 200 ℃, and the chemical bonding and crystal structure of the thin films were analyzed. As the amount of nitric acid added increased, the thickness of the thin film decreased. As the thickness of the hole transfer layer decreased, the photoelectric conversion efficiency of the perovskite solar cell improved. The maximum photoelectric conversion efficiency of the perovskite solar cell having an MoO3 thin film was 4.69 % when the conditions of hydrothermal synthesis were 150 ℃ and mass ratio of AMT : nitric acid of 1 : 12 wt%.

Current progress in Cu 2 BaSn(S, Se) 4 thin film

The inexhaustible solar energy is regarded as a candidate to displace the diminishing fossil fuel resources and reduce greenhouse emissions. Photovoltaic and photoelectrochemical process provide a pathway for directly converting solar light into electricity power and clean hydrogen energy. It is significant to explore a promising and abundant material for utilization the solar energy. Cu2ZnSn(S, Se)4 has a direct bandgap, suitable bandgap (1.0–1.5 eV), high absorption efficient, which has been used as a absorbed layer in thin film solar cell achieving a power conversion efficiency of 12.6% and a photocathode gaining a photocurrent density of 13 mA/cm2. However, the close ionic sizes between Cu+ (0.91 A) and Zn2+ (0.88 A) in Cu2ZnSn(S, Se)4 leads to the antisite disorder and associated band tailing, and limits the performance improvement. According to the theoretical calculation, substituted the Cu or Zn with the large radius atom can efficiently reduce the antisite disorder. The large Ba substitutes Zn in Cu2ZnSn(S, Se)4 forming Cu2BaSn(S, Se)4, which can suppress the antisite defects. According to the Schockley-Queisser theory, the photocurrent density of the photocathode based on bare Cu2BaSn(S, Se)4 thin film is 14.5 mA/cm2 under AM 1.5G illumination and the maximum power conversion efficiency of the thin film solar cell based on a pure Cu2BaSn(S, Se)4 ( E g =2.0 eV) is 22%. Therefore, it has attracted a great deal of attentions in Cu2BaSn(S, Se)4 thin films. From a special perspective, this review summarizes the progress of Cu2BaSn(S, Se)4 thin films in recent years. First, we outline the physical properties of Cu2BaSn(S, Se)4. According to the experimental and theoretical results, it reveals that the Cu2BaSn(S, Se)4 has less cationic disordering and associated band tailing than that in Cu2ZnSn(S, Se)4, which indicates the Cu2BaSn(S, Se)4 will be a promising candidate to Cu2ZnSn(S, Se)4. Moreover, the Cu2BaSn(S, Se)4 has two crystal structures and the phase transition from trigonal ( P3 1 ) to orthorhombic ( Ama 2 ) with a increasing Se/(S+Se) ratio. Due to the phase transition, the bandgap decreases with an increasing Se/(S+Se) ratio, achieved a lowest bandgap, then the bandgap increases with an increasing Se/(S+Se) ratio. In other word, the bandgap of Cu2BaSn(S, Se)4 can be controlled by adjusted the Se/(S+Se) ratio. Meanwhile, the Cu2BaSn(S, Se)4 shows a direct bandgap which is beneficial to the performance of photoelectrical devices. Therefore, Cu2ZnSn(S, Se)4 will be an excellent semiconductor material in photoelectrical field. Second, the methods for preparing Cu2BaSn(S, Se)4 thin films is a hot topic. Here, we classified the methods for growing Cu2BaSn(S, Se)4 thin films to physical deposition approach and chemical solution approach. The advantages and disadvantages of the method are summarized in this review. It is worth to noting, the morphology of the thin films is related with the composition of Cu2BaSn(S, Se)4. Third, we summarized the application field of Cu2BaSn(S, Se)4 thin films. For example, the solar cells based on Cu2BaSn(S, Se)4 get a highest power efficiency conversion of 5.2% (total area 0.425 cm2) and the Cu2BaSn(S, Se)4 applied in photoelectrochemical electrode achieved a current-density of 12.08 mA/cm2 at 0 V vs. reversible hydrogen electrode. Finally, we conclude the prospective and challenge in the future.

Integrated Photon Upconversion Dye-Sensitized Solar Cell by Co-adsorption with Derivative of Pt-Porphyrin and Anthracene on Mesoporous TiO2.

Photon upconversion via triplet–triplet annihilation (TTA-UC) is a process that converts two lower-energy photons to a higher-energy photon, which is expected to increase the maximum solar cell efficiency beyond the Shockley–Queisser limit. To incorporate TTA-UC into a dye-sensitized solar cell (DSSC), we used a co-adsorption approach, in which both a TTA-UC donor with an alkyl carboxylic acid chain and a TTA-UC acceptor dye were adsorbed onto mesoporous TiO2. Incident photon-to-current conversion efficiency spectra and excitation intensity dependence indicated that a photocurrent was generated under irradiation at wavelengths above 490 nm by the TTA-UC mechanism. The power-conversion efficiency of the DSSC was increased to 0.72%, and the photocurrent contributed by TTA-UC was 0.036 mA cm–2 under 1 sun irradiation.

Effect of sputtered Cu2ZnSnS4 film thickness on dye sensitized solar cell counter electrode performance

Cu2ZnSnS4 (CZTS) films were deposited on the fluorine doped tin oxide substrates using a two-step process. First step, the Cu/Zn/Sn precursors were coated on conductive glass using a direct-current magnetron sputtering method. Second step, Cu/Zn/Sn films were annealed at 600 °C for 1 h under a sulfur atmosphere. X-ray diffraction and Raman spectroscopy indicated kesterite Cu2ZnSnS4 formation. CZTS films were used as the counter electrodes (CEs) of dye-sensitized solar cells. The solar cell efficiency and the short circuit current density increased with increasing CZTS film thickness. The maximum solar cell efficiency based on CZTS CEs reached 6.27% at film thickness of 3.7 ± 0.8 μm, compared to a Pt based dye-sensitized solar cell of 7.52%.

A promising concept to push efficiency of pn-junction photovoltaic solar cell beyond Shockley and Queisser limit based on impact ionization due to high electric field

This paper studies the implication of impact ionization due to a high electric field on the improvement of the photovoltaic solar cell efficiency. A high electric field existing in the space charge region (SCR) of the solar cell induces the generation of additional free carriers by accelerating the photogenerated electron-hole pairs which collide with the lattice of the semiconductor material. The resultant current taking into account this carriers’ multiplication (CM) is calculated and the maximum efficiency of the photovoltaic solar cell is evaluated. The found results show that CM in photovoltaic solar cell occurs in a definite range of the electric field near to the pn-junction and could improve significantly his efficiency for more than 5% at an electric field less than 4 × 105 V/cm, depending on the width of the space charge region or the multiplication region. The usable range of the electric field for CM in solar cell is linked to the type of semiconductor material used.