One-dimensional Device Simulation Research Articles

Improvement of the Sb2Se3/Si tandem cell and simulation in SCAPS

In the work, tandem solar cells were designed to achieve improved efficiency using Sb2Se3/Si as the materials. The work involved simulating the Sb2Se3/Si structures, where Sb2Se3 served as the top cell and Si as the bottom cell, under AM1.5 G solar spectrum illumination using the one-dimensional device simulator Scaps. The obtained results demonstrated a significant increase in the efficiency of the Sb2Se3/Si tandem solar cell. Initially, the top cell had an efficiency of 14.29%, while the bottom cell had an efficiency of 11.22% when considered as single cells in a row. When used in tandem, the efficiency of the Sb2S3/Si tandem cell improved to 14.6%. Additionally, there were notable improvements in the electrical parameters of the solar cell. The overall efficiency (ƞ) reached 21.41%, the open-circuit voltage (Voc) was 1.37volts, the short-circuit current density (Jsc) was 19.78 mA/cm2, and the fill factor (FF) reached 78.62%. These results highlight the success of the Sb2S3/Si tandem solar cell in achieving higher efficiency and improved electrical performance compared to single cells.

Structural design of BaSi2 solar cells with a-SiC electron-selective transport layers

Sputter-deposited polycrystalline BaSi2 films capped with a 5 nm thick a-SiC layer showed high photoresponsivity. This means that the a-SiC layer functions as a capping layer to prevent surface oxidation of BaSi2. Based on the measured absorption edge, the electron affinity of the a-SiC layer, and the work function of the TiN layer, the a-SiC is considered to act as an electron transport layer (ETL) for the BaSi2 light absorber layer/a-SiC interlayer/TiN contact structure in a BaSi2 solar cell. Using a 10 nm thick p+-BaSi2 layer as a hole transport layer, we investigated the effect of the BaSi2/a-SiC layered structure on the device performance of a BaSi2-pn homojunction solar cell by a one-dimensional device simulator (AFORS-HET v2.5). The a-SiC ETL effectively separates photogenerated carriers and allows transport of electrons while blocking holes to achieve an efficiency of 22% for a 500 nm thick BaSi2 light absorber layer.

Comparison from Simulated Al0.3Ga0.7As/GaAs/Ge and Al0.3Ga0.7As/GaAs/Si/Ge to Experimental InGaP/GaAs/InGaNAsSb/Ge for Optimized Utilization of the Solar Spectrum

To make full use of the solar spectrum, the performances of Al0.3Ga0.7As/GaAs/Ge and Al0.3Ga0.7As/GaAs/Si/Ge have been simulated using a one-dimensional device simulator called personal computer oe dimension (PC1D). The dependencies of simulated current density–voltage (J–V) and external quantum efficiency (EQE) results on the thicknesses of each sub-cell have been thoroughly analyzed to determine the preferred thickness. Compared to Al0.3Ga0.7As/GaAs/Ge (1.5/5/50 μm), Al0.3Ga0.7As/GaAs/Si (1.5/5/180 μm) has an increase of 0.36 V for open-circuit voltage (Voc) but a slight decrease of 1.55 mA/cm2 for short-circuit current density (Jsc). Subsequently, a monolithic InGaP/GaAs/InGaNAsSb (1.9/1.42/1 eV, 3 J) cell has been mechanically stacked on a Ge cell with four terminals. The Jsc value of 14 mA/cm2 and 6.5 mA/cm2 is calculated for each sub-cell of 3 J cell and bottom Ge cell with integration of EQE measurements. In addition, the TiO2/SiO2/TiO2 (150 nm/1 µm/150 nm, trilayer) interface provides a thermal conductance (2.9 × 106 W K−1) comparable to the direct bond interface. It is believed that the architecture of InGaP/GaAs/InGaNAsSb on the Ge cell with a trilayer interface between is the preferred choice.

A numerical optimization study of CdS and Mg0.125Zn0.875O buffer layers in CIGS-based solar cells using wxAMPS-1D package

ABSTRACT The performance of copper indium gallium selenium (CIGS) based solar cells with cadmium sulfide (CdS) and magnesium zinc oxide (Mg x Zn1-x O) buffer layers has been investigated comparatively with the new version of a one-dimensional device simulation program for the analysis of microelectronic and photonic structures (wxAMPS-1D). The structures of solar cells have been analysed keeping in view the effect of doping as well as of thickness of buffer and absorber layers. It is observed that the conversion efficiency and external quantum efficiency (EQE) are improved using Mg0.125Zn0.875O compound buffer layer for ZnO/Mg0.125Zn0.875O/CIGS structure to 22.01% and 89.7%, respectively, whereas the obtained conversion efficiency and EQE for ZnO/CdS/CIGS structure are 21.06% and 88.78%, respectively. The obtained results are in good agreement with the recently published work and the proposed structure of solar cells would have potential regarding improvements in the existing solar cell technology.

Solis: a modular, portable, and high-performance 1D semiconductor device simulator

This article presents Solis, a new modular, fast, and portable one-dimensional (1D) semiconductor device simulator designed and developed particularly for photovoltaic solar cells. Solis is coded in standard C++, runs natively on Windows and Linux, and is freely available to download. All the physical models and excitation parameters can be fully controlled using the fast embedded Lua scripting engine. Solis includes a useful set of tools coded in C, such as a code editor, graphical device editor, and data plotter. A material parameters database including well-known semiconductors and their alloys is also included. The Solis calculation engine implements the drift–diffusion transport model and takes into account indirect recombination processes (with user-defined deep or shallow levels) as well as radiative and Auger recombination. The anode and cathode parameters, including the refractive index, extinction coefficient, recombination speed, and barrier height for the Schottky contact, are fully included. It natively handles spontaneous and piezoelectric polarization, which is key for the development of devices based on wurtzite materials. The values of all the material parameters can be graded arbitrarily in position, offering flexibility for the simulation of heterostructure solar cells. In addition, Solis offers functionality needed by researchers to analyze the simulation results, including graphing (of the band diagram, carrier concentration, ionized dopant and trap concentrations, current–voltage and capacitance–voltage characteristics, quantum efficiency, etc.) with complete control of the graph and a useful mathematical console. Solis simulation results for a solar cell using Earth-abundant elements are presented herein. One of the main issues in the development of such solar cells, viz. the inhomogeneity due to phase separation in the absorber, is highlighted.

Minimizing performance degradation induced by interfacial recombination in perovskite solar cells through tailoring of the transport layer electronic properties

The performance of hybrid organic-inorganic metal halide perovskite solar cells is investigated using one-dimensional drift-diffusion device simulations. We study the effects of interfacial defect density, doping concentration, and electronic level positions of the charge transport layer (CTL). Choosing CTLs with a favorable band alignment, rather than passivating CTL-perovskite interfacial defects, is shown to be beneficial for maintaining high power-conversion efficiency, due to reduced minority carrier density arising from a favorable local electric field profile. Insights from this study provide theoretical guidance on practical selection of CTL materials for achieving high-performance perovskite solar cells.

Effect of wide band-gap TCO properties on the bifacial CZTS thin-films solar cells performances

In this work, one-dimensional device simulator AMPS-1D was employed to study the electrical and optical properties of bifacial ZnO:Al/CdS/Cu2ZnSnS4 (CZTS)/TCO/SLG thin film solar cells. The impact of barrier height in the CZTS/TCO interface has been investigated for front and back side illuminations. The combination of the optical transparency and the electrical properties for the TCO back contact layer are capable of yielding high efficiency. The presence of barriers in the CZTS/TCO back-side interface of the structure can significantly affect the cell performance by limit the carriers current flow. The optimum CZTS absorber layer thickness used in the simulation has been calculated. The best energy conversion efficiency has been calculated in the case of front and back side illuminations. In the case of front side illumination, an efficiency of 15.8% (withVoc≈0.93V,Jsc≈18.7mA/cm2, FF≈0.77 and QE≈82.5% at 570nm) have been obtained with a barrier height close to 0.4eV. In the case of back side illumination, we notice a low performances. For 0.4eV barrier height, we obtain 1.8% (withVoc≈0.95V,Jsc≈2.6mA/cm2, FF≈0.74 and QE≈20.6% at 820nm). Without barrier height we obtain a maximum of efficiency (η≈4%) in the case of back side illumination. All these simulation results give some important indication to lead a higher efficiency of bifacial CdS/CZTS/TCO structure for feasible fabrication.

Investigation of p-type emitter layer materials for heterojunction barium disilicide thin film solar cells

To achieve heterojunction thin film solar cells with high conversion efficiency using BaSi2 as a photoabsorption layer, we investigated the effects of electron affinity (χ) and the band gap (Eg) of a p-type semiconductor on the performance of BaSi2 thin film solar cells with a one-dimensional device simulator, Afors-HET ver. 2.5. By simulation, we found that χ should be less than 3.5 eV and Eg should be in the range of 1.5–2.5 eV to achieve a conversion efficiency of more than 20% in the case of p-type semiconductor/n-type BaSi2 active layer/n++-type BaSi2/electrode. Ultimately, we selected Zn3P2 (Eg = 1.5 eV, χ = 3.2 eV) and SnS (Eg = 1.3 eV, χ = 3.6 eV) as options for p-type materials. In particular, Zn3P2 maintains high efficiency even if a very thin oxide layer exists at the pn heterointerface. The highest conversion efficiency of p-type Zn3P2/n-type BaSi2 thin film solar cells was 23.17% without any light-trapping structure.

Simulation design of P–I–N-type all-perovskite solar cells with high efficiency**Project supported by the Graduate Student Education Teaching Reform Project, China (Grant No. JG201512) and the Young Teachers Research Project of Yanshan University, China (Grant No. 13LGB028).

According to the good charge transporting property of perovskite, we design and simulate a p–i–n-type all-perovskite solar cell by using one-dimensional device simulator. The perovskite charge transporting layers and the perovskite absorber constitute the all-perovskite cell. By modulating the cell parameters, such as layer thickness values, doping concentrations and energy bands of n-, i-, and p-type perovskite layers, the all-perovskite solar cell obtains a high power conversion efficiency of 25.84%. The band matched cell shows appreciably improved performance with widen absorption spectrum and lowered recombination rate, so weobtain a high Jsc of 32.47 mA/cm2. The small series resistance of the all-perovskite solar cell also benefits the high Jsc. The simulation provides a novel thought of designing perovskite solar cells with simple producing process, low production cost and high efficient structure to solve the energy problem.

The effect of skin-depth interfacial defect layer in perovskite solar cell

The hole transport buffer layer (HTL) known as PEDOT:PSS is found to be sensitive to polar solvents often used in the preparation of solution-processed perovskite-based solar cell. We employed \(\hbox {CH}_{3}\,\hbox {NH}_{3}\,\hbox {PbI}_{3}\) perovskite absorber sandwiched between two charge transport layers to analyze the effect of precursor solvent. By introducing skin-depth interfacial defect layer (IDL) on PEDOT:PSS film we studied the overall performance of the devices using one-dimensional device simulator. Both enhanced conductivity and variations in valence band offset (VBO) of IDL were considered to analyze device performance. A power conversion efficiency (PCE) of the devices was found to grow by 35 % due to increased conductivity of IDL by a factor of 1000. Furthermore, we noted a drastic reduction in PCE of the device by reducing the work function of IDL by more than 0.3eV . The thickness of interfacial defect layer was also analyzed and found to decrease the PCE of the devices by 18 % for fourfold increase in IDL thickness. The analysis was remarkably reproduced the experimentally generated device parameters and will help to understand the underlying physical process in perovskite-based solar cell.

Theoretical analysis on effect of band offsets in perovskite solar cells

The effect of band offsets in CH3NH3PbI3-xClx perovskite-based solar cells with planar junction configuration was analyzed using one-dimensional device simulator. As widely known in thin-film compound solar cells, the band offset between buffer/absorber layers is a decisive factor for carrier recombination at the interface, determining open-circuit voltage (Voc). In this study, the impact of two kinds of band offsets, i.e., the conduction band offset of buffer (or blocking layer)/absorber layers and the valence band offset of absorber/hole transport material (HTM) were examined. When the conduction band of the buffer was lower than that of the absorber, the interface recombination became prominent and Voc decreased. In contrast, when the conduction band of the buffer was higher than that of the absorber by more than 0.3eV, the collection of photo-generated carriers, i.e. electron in this case, was impeded by the spike formed by the conduction band offset. Thus, the optimum position of the conduction band of the buffer was 0.0~0.3eV higher than that of the absorber. Also, the optimum position of the valence band of the HTM was derived to be 0.0~0.2eV lower than that of the absorber. These findings will be useful for new material choice and optimization of buffers and HTMs.

Device modeling of perovskite solar cells based on structural similarity with thin film inorganic semiconductor solar cells

Device modeling of CH3NH3PbI3−xCl3 perovskite-based solar cells was performed. The perovskite solar cells employ a similar structure with inorganic semiconductor solar cells, such as Cu(In,Ga)Se2, and the exciton in the perovskite is Wannier-type. We, therefore, applied one-dimensional device simulator widely used in the Cu(In,Ga)Se2 solar cells. A high open-circuit voltage of 1.0 V reported experimentally was successfully reproduced in the simulation, and also other solar cell parameters well consistent with real devices were obtained. In addition, the effect of carrier diffusion length of the absorber and interface defect densities at front and back sides and the optimum thickness of the absorber were analyzed. The results revealed that the diffusion length experimentally reported is long enough for high efficiency, and the defect density at the front interface is critical for high efficiency. Also, the optimum absorber thickness well consistent with the thickness range of real devices was derived.

Simulation and performance analysis of superstrate Cu(In,Ga)Se<SUB align="right">2 solar cells using nanostructured Zn<SUB align="right">1−xV<SUB align="right">xO thin films

In this paper, we describe in the first step the structural, electrical and optical properties of the nanostructured Zn 1– x V x O thin films deposited on glass substrates by rf-magnetron sputtering using aerogel nanoparticles synthesised by the sol–gel method. The best properties, satisfying the role of window and buffer layers, were achieved, respectively, for the films of Zn 0.99 V 0.01 O elaborated at room temperature and Zn 0.80 V 0.20 O at 200ºC. In the second step, the nanostructured Zn 0.99 V 0.01 O and Zn 0.80 V 0.20 O layers are, respectively, proposed as alternative to the traditional (ITO) window and (CdS) buffer layers and tested numerically in Cu(In,Ga)Se 2 (CIGS) solar cell using one-dimensional AMPS-1D device simulator. The influence of physical and geometrical parameters of the p -type CIGS absorber layer on the performance of the superstrate SLG/(n+)Zn 0.99 V 0.01 O/(n)Zn 0.80 V 0.20 O/(p)Cu(In,Ga)Se 2 /Mo solar cell was investigated. The calculations assume fixed Zn 1– x V x O input parameters. The carrier concentration and thickness of the absorber layer were found to be a key factor, affecting the solar cell performance. On the basis of the simulation results, a short-circuit current density of about 33 mA/cm 2 has been obtained for 4 µm-CIGS solar cell using n -type Zn 0.80 V 0.20 O buffer layer for 100 nm thick. It is also found that a conversion efficiency of more than 19% AM 1.5 G could be expected for more than 3 µm absorber thickness and acceptor concentration varying between 2 × 10 16 and 10 17 cm –3 . From the results obtained, we suggest the use of Zn 0.80 V 0.20 O and Zn 0.99 V 0.01 O as a buffer and window layers, respectively, to achieve high-efficiency CIGS solar cells with better photovoltaic parameters.

One-dimensional simulation of sequentially processed [formula omitted] heterojunction solar cells with vertically graded absorber composition

The successful definition and verification of a one-dimensional device simulation baseline for sequentially processed Mo/Cu(In1−xGax)(Se1−ySy)2/CdS/i-ZnO/ZnO:Al thin film solar cells is presented. The appropriate modeling of the layer sequence requires experimental assessment of the relevant material properties of each film within the layer sequence of the device. The properties of the CdS/i-ZnO/ZnO:Al window layer stack and of the molybdenum back electrode have been approximated by their bulk properties obtained from experiment and from the literature, respectively. This approach is, however, not meaningful for the sequentially processed Cu(In1−xGax)(Se1−ySy)2 (CIGSSe) thin films due to characteristic segregation/grading of the chemical composition and the presence of structural inhomogeneities. This work shows that a suitable modeling of the CIGSSe film can be achieved by definition of effective medium properties. With this approach a 1D device simulation baseline for the studied system was established, which accurately reproduces the experimental characteristics of the studied CdS/CIGSSe heterojunction solar cells.

Mechanism of the Improvement in Microcrystalline Silicon Solar Cells by Hydrogen Plasma Treatment

We explain the experimental improvement in long wavelength response by hydrogen plasma treatment (HPT) in n/i interface. The absorption coefficient of the intrinsic microcrystalline silicon (μc-Si) is decreased in the low energy region (0.8~1.0 eV) by HPT, which indicates a lower defect density in μc-Si layer deposited with HPT than its counterpart without HPT. Simulation by one-dimensional device simulation program for the Analysis of Microelectronic and Photonic Structures (AMPS-1D) shows a higher long wavelength response in μc-Si solar cell if the defect density in intrinsic μc-Si layer is smaller. Our simulation results also disclose that the less defect density in intrinsic layer, the lower recombination rate and the higher electric field is. Higher electric field results in longer drift length which will promote collection of carriers generated by photons with long wavelength. Thus we deduce that HPT decreased defect density in absorber layer and improved the performance of μc-Si solar cells in long wavelength response.

Influence of Surface Recombination on the Performance of SiNW Solar Cells and the Preparation of a Passivation Film

ABSTRACTAl2O3 was deposited on silicon nanowire (SiNW) arrays by atomic layer deposition (ALD) as a passivation layer to reduce surface recombination velocity. As a result, effective minority carrier lifetime was improved from 1.82 to 26.2 μs. From this result, the relative low-surface recombination rate of 2.73 cm/s was obtained from a calculation using one-dimensional device simulation (PC1D). The performance of SiNW solar cells was also simulated by considering the surface recombination velocity on the side of SiNWs using two-dimensional device simulation. It was found that Al2O3 deposited by ALD can improve open-circuit voltage of SiNW solar cells even if the structure has a high-aspect ratio and large surface area. Therefore, improvement in the performance of SiNW solar cells can be expected.

Modeling of degradation behavior of InGaP/GaAs/Ge triple-junction space solar cell exposed to charged particles

Degradation modeling of InGaP/GaAs/Ge triple-junction (3J) space solar cells, which are exposed to charged particles (protons and electrons), is introduced using a one-dimensional optical device simulator: PC1D. The proposed method can reproduce the electrical degradation of 3J solar cells from fitting the external quantum efficiencies for subcells. In this modeling, carrier removal rate of base layer (RC) and damage coefficient of minority carrier diffusion length (KL) in each subcell are considered as radiation degradation parameters. Nonionizing energy loss (NIEL) analysis for both radiation degradation parameters is discussed. The radiation degradation of a 3J solar cell can be predicted from the results of degradation level in the each subcell estimated from correlativity between NIEL and both radiation degradation parameters.

Degradation modeling of InGaP/GaAs/Ge triple-junction solar cells irradiated with various-energy protons

Degradation modeling of InGaP/GaAs/Ge triple-junction (3J) solar cells subjected to proton irradiation is performed with the use of a one-dimensional optical device simulator, PC1D. By fitting the external quantum efficiencies of 3J solar cells degraded by 30 keV, 150 keV, 3 MeV, or 10 MeV protons, the short-circuit currents ( I SC) and open-circuit voltages ( V OC) are simulated. The damage coefficients of minority carrier diffusion length ( K L ) and the carrier removal rate of base carrier concentration ( R C) of each sub-cell are also estimated. The values of I SC and V OC obtained from the calculations show good agreement with experimental values at an accuracy of 5%. These results confirm that the degradation modeling method developed in this study is effective for the lifetime prediction of 3J solar cells.

Equivalent circuit model for an insulated gate bipolar transistor

An equivalent-circuit model for an insulated gate bipolar transistor is developed. The model is based on a one-dimensional device simulation model. It also adopts a multi-MOS model so as to be able to include the doping variation in the MOS body. The model can be used for both circuit simulations and simple device simulations. The simulation results agree with experimental observations.

Amorphous silicon junction field-effect transistor with low pinch-off voltage for analog applications

In this paper we report on the modeling and formation of a junction field effect transistor for linear circuits based on amorphous silicon materials. Although the device behaves basically as the corresponding crystalline device, modeling of the depletion process of the channel, controlling the device operation, has to be performed in order to take into account the effect of the high defect density in doped amorphous silicon. To this aim, we used a one-dimensional finite-difference device simulator, which provides design specifications for a transistor which works properly with a few volts for both drain/source voltage and gate/source voltage. Based on simulation results a device with W/ L=400 μm/40 μm was fabricated. The measured output characteristics show pinch-off voltages around −3.6 V and transconductance values of the order of 10 −7 A/V. These performances are better than the ones obtained from state of the art thin-film transistor and make the device suitable for application as amplifier.