Quantum Efficiency Of Solar Cells Research Articles

The Fabrication and Characterization of Silicon Surface Grooving Using the CV Etching Technique for Front Deep Metallic Contact Solar Cells

This study experimentally investigated the use of the chemical vapor etching method for silicon surface grooving for regular front deep metallic contact solar cell applications. The thickness of silicon wafers is a crucial parameter in the production of solar cells with front and back buried contacts, because silicon surface grooves result in a larger contact area, which in turn improves carrier collection and increases the collection probability for minority carriers. A simple, low-cost HNO3/HF chemical vapor etching technique was used to create grooves on silicon wafers with the help of a highly effective anti-acid mask. The thick porous layer of powder that was produced was easily dissolved in water, leaving patterned grooved areas on the silicon substrate. A linear dependence was observed between the etched thickness and time, suggesting that the etching process followed a constant etch rate, something that is crucial for ensuring precise and reproducible etching results for the semiconductor and microfabrication industries. Moreover, by creating shorter pathways for charge carriers to travel to their respective contacts, front deep contacts minimize the overall distance they need to traverse and therefore reduce the chance of carrier recombination within the silicon material. As a result, the internal quantum efficiency of solar cells with front deep metallic contacts improved by 35% compared to mc-Si solar cells having planar contacts. The use of front deep contacts therefore represents a forward-looking strategy for improving the performance of silicon solar cells. Indeed, this innovative electrode configuration improves charge carrier collection, mitigates recombination losses, and ultimately leads to more efficient and effective solar energy conversion, which contributes to sustainable energy development in the areas of clean energy resources. Further work needs to be undertaken to develop energy sustainably and consider other clean energy resources.

Experimental Confirmation of the Optoelectronic Reciprocity Theorem in High-Efficiency CuIn1−xGaxSe2 Solar Cells

The optoelectronic reciprocity theorem has been proposed as a theorem relating electroluminescence (EL) and photovoltaic external quantum efficiency in solar cells. The theorem is vital for a fundamental understanding of solar cell operation and its application to device evaluation. Furthermore, with this theorem, it is also possible to estimate the open-circuit voltage (${V}_{\mathrm{OC}}$) of solar cells using the external radiative efficiency (${\ensuremath{\eta}}_{\mathrm{ext}}$) obtained from the absolute value of EL emission intensity, even for solar cells for which we cannot directly measure ${V}_{\mathrm{OC}}$, such as subcells of multijunction solar cells or individual $\mathrm{Si}$ cells in modules and arrays. However, it is not a priori obvious that the optoelectronic reciprocity theorem holds for the various solar cells that exist. In this study, we report the results of qualitative and quantitative confirmation of the validity of the optoelectronic reciprocity theorem for high-efficiency ${\mathrm{Cu}\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}{\mathrm{Se}}_{2}$ (CIGS) solar cells fabricated by us. The results confirm that our CIGS solar cells qualitatively and quantitatively satisfy the optoelectronic reciprocity theorem within the limits of measurement uncertainty. Also, we experimentally confirm that the value of the diode ideality factor for the applied voltage dependence of the EL emission intensity is exactly unity when the emission mechanism is the band-edge emission due to the direct recombination of electron-hole pairs. Finally, the importance of the ${\ensuremath{\eta}}_{\mathrm{ext}}$ for improving solar cell efficiency is explained.

Numerical and Experimental Study of the Front Surface Recombination Velocities and Base Widths Effect in Multi-Crystalline Silicon Solar Cell Quantum Efficiency

Photovoltaic research activities are related to material innovation that can be obtained at a comparatively low cost. Semiconductor p-type multi-crystalline Czochralskyc (CZ)-grown silicon wafers were used in this study. The effects of front surface recombination velocities and base thickness in solar cells’ quantum efficiency are theoretically calculated. The results denote that both the surface recombination velocities and the base widths significantly impact the quantum efficiency. The results are of universal technical importance in designing solar cells and their surface structures. The main goal of this paper was to confirm the validity of the above theoretical calculations; for this purpose, silicon solar cells with front-thin porous silicon and rear interdigitated contact have been produced. A good agreement was obtained between experimentally obtained solar cells’ quantum efficiency data and the theoretical results. Therefore, the quantum efficiency of the mc-Si solar cells with porous silicon and rear interdigitated contact was enhanced up to 25% at 580–1100 nm wavelength range and up to 50% at short wavelength (400–570 nm), compared to reference mc-Si solar cells. The obtained results indicate that the rear interdigitated contact maximizes the surface area of the metal contact and improves the current collection. At the same time, the porous silicon layer passivates the front surface and reduces recombination losses.

Rapid thermal oxidation of nano silver film for solar cell fabrication

In this paper, the nano Silver dioxides films have been deposited using the reactive pulsed laser deposition method (RPLD) using the tattoo removal Q-swithing Nd-Yag laser, at the value of the wavelength of 1064nm, pulseduration of 6 sec, and 800 mJ energy of laser have been applied for ablated an extra purity of the Silver target then deposited the nano siver oxide particles on the silicon substrates, synthesize and studying of the rapid thermal annealing (RTA) effects on the structural properties, the morphological properties, the Optical properties, the electrical properties and finally the solar cell properties for the prepared samples. Both X-ray diffraction and electron microscopy studies show that the structure of the film depends on the annealing teamperatures effects of the deposited film. The nano silver oxide is present in different crystalline stages, where the particle sizes have been increases with increasing heat treatment from 45nm to 75 nm. The analized Results of the optical aprove the improvements of the absorption lead to decreasing the reflection values compared with the surface of the silicon (crystalline Si), where the transparency for the range of larger than 300 nm and the values of the optical band gap of 2.12 eV. The synthesized results for the solar cell fabrications present a clear improvement in the solar cell quantum efficiency values in the case of silver nano oxide deposition and annealed with the high degree, where the value of the efficiency about of 4.22.

Refined optoelectronic properties of silicon nanowires for improving photovoltaic properties of crystalline solar cells: a simulation study

Tremendous works have been devoted on reducing the materials costs and searching a low-cost antireflection (AR) layer in silicon (Si) solar cells. This work reports on the surface architectural of Si wafer (p-type) by growing the nanowires (NWs)-like structures through cost-effective wet-controlled etching method. The nanostructures over Si wafer were optimized in terms of sizes, lengths and densities by changing the etching conditions and thoroughly examined their growth and optoelectrical properties. The well-defined grown NWs textured on Si wafer exhibited the low average reflectance of ~ 2.25% in the full visible-NIR spectrum from 400 to 1000 nm which was well matched to the simulated average reflectance of 2.23%. A model was designed using PC1D simulation to evaluate the photovoltaic (PV) parameters of NWs textured Si wafer-based solar cells without AR layer. In this simulation, the length of SiNWs and reflectance were selected as input parameters to instigate the power conversion and quantum efficiencies of solar cells. The highest conversion efficiency of ~ 16.2% is observed when the average length of SiNWs and reflectance were ~ 2.52 μm and ~ 2.25%, respectively. Experimentally, the fabricated SiNWs-based solar cell with etching time of 20 min attained the highest conversion efficiency of 15.9% and the value was very close to simulated results. PV parameters of SiNWs-based solar cells without AR layer were comparable to commercial c-Si solar cells with SiNx AR layer. Thus, the controlled wet etching is an easy, facile method for fabrication of nanowires on Si wafer with low reflectance. The enhancement in optical and electrical properties would be expected to a great prospect in developing low-cost c-Si solar cells without AR layer.

Manual Method for Measuring The External Quantum Efficiency for solar cells

Nowadays, the research related to the solar cells is oriented to the solar cell’s quantum efficiency (QE) or the Incident Photon to Charge Carrier Efficiency (IPCE) development. The determination of the external quantum efficiency (EQE) is fundamental to photovoltaic research [10]. This article proposes a fast conventional method to determine the external quantum efficiency (EQE) of a solar cell using a measuring bench (IPCE), such as the instruments and the measuring principle. The foundations necessary to study the important parts of EQE are built. The main equations and guiding principles of this measurement are reviewed.

Perovskite Single-Crystal Thin Film Devices Using Lithography Assisted Epitaxy

Strain engineering is an emerging technique to physically manipulate and enhance semiconductor device performance. Chen et al. recently combined strain engineering with halide perovskites, demonstrating a novel approach toward improvement in optoelectronic properties.

Towards intermediate-band photovoltaic absorbers: theoretical insights on the incorporation of Ti and Nb in In2S3

Creation of a partially filled intermediate band in a photovoltaic absorber material is an appealing concept for increasing the quantum efficiency of solar cells. Recently, we showed that formation of a partially filled intermediate band through doping a host semiconductor with a transition metal dopant is hindered by the strongly correlated nature of d-electrons and the antecedent Jahn–Teller distortion, as we have previously reported. In present work, we take a step forward and study the delocalization of a filled (valence-like) intermediate band throughout the lattice: a case study of Ti- and Nb-doped In2S3. By means of hybrid density functional calculations, we present extensive analysis on structural properties and interactions leading to electronic characteristics of Ti- and Nb-doped In2S3. We find that Nb creates an occupied doublet, which can become delocalized onto the crystal at high but feasible concentrations (around 2.5 at% and above). As a consequence, doping In2S3 with adequately high concentrations of Nb allows the subgap intermediate band to conduction band absorption, which leads to higher photocurrent densities compared to pure In2S3. Ti on the other hand forms an occupied singlet intermediate band, which remains strongly localized even at high concentration of 5 at%.

Establishment and evaluation of photovoltaic quantum efficiency system at central metallurgical research and development institute

A system for measuring the spectral responsivity and quantum efficiency of solar cells is described. We have developed and characterized a traceable measurement setup for measuring the spectral responsivity S(λ) and photovoltaic quantum efficiency at Central Metallurgical Research and Development Institute (CMRDI); we report experimental measurements for spectral responsivity, reflectance, and quantum efficiency measurements covering the wavelength from 300 nm to 1800 nm. For this purpose, we adapted and improved a system designed to measure the External Quantum Efficiency (EQE) and the Internal Quantum Efficiency (IQE) of different types of solar cells as the determination of the spectral responsivity is an essential part of solar cell characterization. Furthermore, this research discusses a procedure for measuring the spectral responsivity of Si and InGeAs detectors used as a reference cell for spectral responsivity and photovoltaic quantum efficiency measurements of solar cells. The system construction and its associated uncertainty budget are described as estimated in detail.

Femtosecond-Laser-Induced Precipitation of CsPbBr3 Perovskite Nanocrystals in Glasses for Solar Spectral Conversion

Inorganic perovskite quantum dots (QDs) and nanocrystals (NCs) have attracted much attention in recent years because of their high photoluminescence (PL) quantum yield (QY), narrow full width at half-maximum, and wide tunability across the whole visible range. In this work, space- and size-controlled precipitation of CsPbBr3 perovskite NCs was realized through a femtosecond laser-direct-writing method. Precipitation of CsPbBr3 NCs in glasses was confirmed by energy-dispersive spectroscopy, transmission electron microscopy analysis, and PL. Growth of CsPbBr3 perovskite NCs in glasses was modulated by femtosecond laser irradiation parameters such as the repetition rate, pulse energy, and scanning rate, and PL in the range spanning from blue to green was achieved. With the well-designed arrangement of CsPbBr3 NCs and the reduction of self-absorption emission, a solar concentrator fabricated by femtosecond laser irradiation can realize spectral conversion and enhance the quantum efficiency of solar cells.

Simulation and application of external quantum efficiency of solar cells based on spectroscopy

In this study, a method for optical simulation of external quantum efficiency (EQE) spectra of solar cells based on spectroscopy is proposed, which is based on the tested transmittance and reflectance spectra. First, to obtain a more accurate information of refractive index and extinction coefficient values, we modified the reported optical constants from the measured reflectance and transmittance spectra. The obtained optical constants of each layer were then collected to simulate the EQE spectra of the device. This method provides a simple, accurate and versatile way to obtain the actual optical constants of different layers. The EQE simulation approach was applied to the flat and textured heterojunctions with intrinsic layers (HIT) solar cells, respectively, which showed a perfect matching between the calculation results and the experimental data. Furthermore, the specific optical losses in different devices were analyzed.

How to Report Record Open‐Circuit Voltages in Lead‐Halide Perovskite Solar Cells

AbstractOpen‐circuit voltages of lead‐halide perovskite solar cells are improving rapidly and are approaching the thermodynamic limit. Since many different perovskite compositions with different bandgap energies are actively being investigated, it is not straightforward to compare the open‐circuit voltages between these devices as long as a consistent method of referencing is missing. For the purpose of comparing open‐circuit voltages and identifying outstanding values, it is imperative to use a unique, generally accepted way of calculating the thermodynamic limit, which is currently not the case. Here a meta‐analysis of methods to determine the bandgap and a radiative limit for open‐circuit voltage is presented. The differences between the methods are analyzed and an easily applicable approach based on the solar cell quantum efficiency as a general reference is proposed.

The research and fabrication of graphene quantum dots applied as the hole transporting layer in polymer solar cells

In this report, we studied and fabricated graphene quantum dots by improved the Hummer method using NH3 reducing agent. The diameter of graphene quantum dots was approximately 6 nm, applied as the hole transport layer in organic solar cell to improve the quantum efficiency of solar cells. GQDs were very friendly with environment, made at low temperatures and might be dried into powder form and dissolved well in polar solvents. Graphene quantum dots with a 0D structure had the workfunction suistable for the conductive polymer which increased the short current (from 2.41 mA/cm2 to 4.38 mA/cm2) of polymer solar cells. They improved the performance significantly compared to conventional solar cells.

The influence of emitter resistance on the electrical parameters of mono- and multicrystalline silicon solar cells

Purpose The purpose of this study was the comparison and analysis of the electrical parameters of two kinds of silicon solar cells (mono- and multicrystalline) of different emitter resistance. Design/methodology/approach By controlling of diffusion parameters, silicon mono- (Cz-Si) and multicrystalline (mc-Si) solar cells with different emitter resistance values were produced – 22 and 48 Ω/□. On the basis of current-voltage measurements of cells and contact resistance mapping, the properties of final solar cells based on two different materials were compared. Additionally, the influence of temperature on PV cells efficiency and open circuit voltage (Uoc) were investigated. The PC1D simulation was useful to determine spectral dependence of external quantum efficiency of solar cells with different emitter resistance. The silicon solar cells of 25 cm2 area and 240 µm thickness were investigated. Findings Considering the all stages of cell technology, the best structure is silicon solar cell with sheet resistance (Rsheet) of 45-48 Ω/□. Producing of an emitter with this resistance allowed to obtain cells with a fill factor between 0.725 and 0.758, Uoc between 585 and 612 mV, short circuit current (Isc) between 724 and 820 mA. Originality/value Measurements and analysis confirmed that mono- and multicrystalline silicon solar cells with 48 Ω/□ emitter resistance have better parameters than cells with Rsheet of 22 Ω/□. The contact resistance is the highest for mc-Si with Rsheet of 48 Ω/□ and reaches the value 3.8 Ωcm.

Different Dissociation Rates of Singlet and Triplet Excitons of Pentacene at the Interface in Solar Cells

Fission of the lowest-energy singlet exciton (S1) to two lowest-energy triplet excitons (T1) in pentacene has been expected to be a promising means for increasing the quantum efficiency of solar cells. Experiments find that S1 and T1 dissociate at quite different time scales at the donor/acceptor interface. Using the pentacene/TiO2 heterojunction as the model, we investigate the dissociation of pentacene excitons by a combination of many-body Green’s function theory and the time-dependent Schrodinger equation. Singlet and higher-energy triplet (Tn) excitons of pentacene could dissociate at the same timescale of ∼100 fs, benefiting from their capability to scatter into charge-transfer (CT) states and weakly bound charge-separated (CS) states across the interface. Resonance of pentacene excitons with CS states could facilitate the creation of free charge carriers. However, dissociation of T1 is hampered due to its poor density of states projected onto the interfacial states, preventing its scattering into C...

Pressure-induced emission of cesium lead halide perovskite nanocrystals

Metal halide perovskites (MHPs) are of great interest for optoelectronics because of their high quantum efficiency in solar cells and light-emitting devices. However, exploring an effective strategy to further improve their optical activities remains a considerable challenge. Here, we report that nanocrystals (NCs) of the initially nonfluorescent zero-dimensional (0D) cesium lead halide perovskite Cs4PbBr6 exhibit a distinct emission under a high pressure of 3.01 GPa. Subsequently, the emission intensity of Cs4PbBr6 NCs experiences a significant increase upon further compression. Joint experimental and theoretical analyses indicate that such pressure-induced emission (PIE) may be ascribed to the enhanced optical activity and the increased binding energy of self-trapped excitons upon compression. This phenomenon is a result of the large distortion of [PbBr6]4− octahedral motifs resulting from a structural phase transition. Our findings demonstrate that high pressure can be a robust tool to boost the photoluminescence efficiency and provide insights into the relationship between the structure and optical properties of 0D MHPs under extreme conditions.

Ultra-Broadband Directional Scattering by Colloidally Lithographed High-Index Mie Resonant Oligomers and Their Energy-Harvesting Applications.

Emerging high-index all-dielectric nanostructures, capable of manipulating light on the subwavelength scale, empower designing and implementing novel antireflection and light-trapping layers in many photonic and optoelectronic devices. However, their performance and practicality are compromised by relatively narrow bandwidths and highly sophisticated fabrications. In this paper, we demonstrate an ultra-broadband (300-1200 nm) directional light scattering strategy using high-index surface silicon oligomer resonators fabricated by a facile, scalable, and low-cost colloidal lithography technique. The exceptional broadband forward scattering stems from a combined effect of strongly intercoupled Mie resonances within the oligomers composed of randomly positioned nanodisks in the visible region and a strong electric mode coupling between the oligomers and the high-index substrate in the red-to-near-infrared region. By implementing this efficient approach in silicon solar cells, the integrated optical reflection loss across the wavelength range 300-1200 nm can be as low as 7%. Consequently, the short-circuit current density determined from the external quantum efficiency of solar cells can be increased to 35.1 from 25.1 mA/cm2, representing an enhancement of 40%, with a demonstrated energy conversion efficiency exceeding 15.0%. The insights in this paper hold great potentials for new classes of light management and steering photonic devices with drastically improved practicality.

Admittance spectroscopy of InGaAsN based solar cells

Single-junction InGaNAs solar cells were grown by MBE with active layers based on a GaAsN/InAs superlattice. Dependence of defect formation on thickness of InGaNAs was explored in the study. Thickness increase from 900 nm to 1200 nm leads to defect formation with two activation energies of 0.20 eV and 0.50 eV but the value of quantum efficiency stays almost the same. Further thickness increase up to 1600 nm leads to the increase of defect concentration in the InGaNAs active layer. These defects are non-radiative recombination centres because a significant decrease of solar cell quantum efficiency was observed. The existence of a critical thickness for defect-free growth of InGaNAs based on GaAsN/InAs superlattice is proposed.

Comparative study on the InGaN multiple-quantum-well solar cells assisted by capacitance-voltage measurement with additional laser illumination

The investigation on the photovoltaic characteristics of two InGaN/GaN multiple-quantum-well (MQW) solar cells with different QW parameters, but having nearly the same spectral response range, is assisted by the capacitance-voltage (C-V) measurements. Based on the laser-assisted C-V technique as well as the X-ray reciprocal space mapping measurements, it is found the enhanced external quantum efficiency of solar cell consisting of the InGaN QWs having thicker well layer and lower In content can be ascribed to the lower effective potential barrier height, the larger active volume and the better material quality. In addition, it suggests that for InGaN MQW solar cells, a proper increase of the InGaN well layer thickness may be a good choice to extend the spectral response into longer wavelength region.

Higher values of spectral response, absorption coefficient and external quantum efficiency of solar cell in the form of pyramids

This paper presents a study on spectral response, absorption coefficient and external quantum efficiency of solar cell in the form of pyramid [1, 2]. We investigate to what extent and under what conditions we want to take advantage of ray incidence Seven times [3, 4]. It is found that these analyses can be used to determine the optimal surface texture which provides the best light trapping for solar cells in terms of the total internal reflection occurring in the high-index medium at incidence angles larger than the nominal critical angle [3–9]. One of the main contributions of this paper is the analysis and quantification of the influence of the opening between the heads of the two closest pyramids in textured surface for solar cells and its application on the photovoltaic parameters. In this model we show that the material can have seven successive incident ray absorptions instead of five currently, where we changed the direction of the reflected ray, by identifying and install the angle between the two neighbouring pyramids, the incidence angle, the opening between the heads of the two closest pyramids and their height. Thus, with an angle between the two neighbouring pyramid fixed at 12° and for angle of incidence fixed at 84°. For these values of the angle between the two neighbouring pyramids and incidence angle, the opening between the heads of the two closest pyramids fixed at 2.10 μm for a pyramid height of 10 μm. This leads to the largest possible increase in optical efficiency, such as spectral response, Absorption Coefficient and External Quantum Efficiency. The results are in good agreement with the available literature.