Double Heterojunction Solar Cells Research Articles

Optimization of Sr3NCl3-based perovskite solar cell performance through the comparison of different electron and hole transport layers

Strontium Nitride Trichloride (Sr3NCl3) is a promising absorber material for solar cells due to its unique structural, electrical, and optical properties. We conducted a thorough investigation to scrutinize the structural, optical, and electronic characteristics and the photovoltaic efficiency of double-heterojunction solar cells utilizing Sr3NCl3 absorbers. Various metals were evaluated for the front and rear contacts to determine the optimal metal-semiconductor interface, with the study determining that silver (Ag) is the most suitable option for the front contact and nickel (Ni) for the back contact. The PV performance of innovative Sr3NCl3 absorber-based cell structures was evaluated with two different Hole Transport Layers (HTLs), MASnBe3 and CBTS, alongside ZnO and WS2 serving as the transition metal dichalcogenide (TMD) Electron Transport Layers (ETLs). This investigation examined a range of factors, such as layer thickness, operational temperature, doping density, defect densities at both the interfaces and within the bulk, carrier generation and recombination rates, quantum efficiency (QE), series versus shunt resistance, absorption coefficient, and current density-voltage (J-V) characteristics, utilizing the SCAPS-1D simulator software. Fine-tuning of both two HTL and ETL revealed that the highest power conversion efficiency (PCE) of 27.34 % with JSC of 19.78 mA/cm2, fill factor (FF) of 88.84 %, and VOC of 1.56 V was achieved with MASnBe3 HTL and ZnO ETL, while the lowest PCE of 25.55 %, with JSC of 19.77 mA/cm2, FF of 89.07 %, and VOC of 1.45 V was obtained for CBTS HTL and WS2 ETL, respectively. These findings highlight the promising potential of Sr3NCl3 absorbers with ZnO as ETL and MASnBe3 as HTL for developing advanced perovskites heterostructure solar cells for enhanced performance in the future.

A novel design and optimization of Si based high performance double absorber heterojunction solar cell

Researchers are currently focusing on Silicon (Si)-based solar cells due to their outstanding semiconductor properties. This study aims to enhance the performance of a new Si based solar cell structure of Cu/FTO/CdS/Si/FeSi2/Au and investigate how the inclusion of FeSi2 as a second absorber and CdS buffer layers affects key performance metrics such as VOC, JSC, FF, and PCE using SCAPS-1D simulation. Various factors including thickness, carrier concentration, defect density, temperature, and electrode design were analyzed in detail to improve performance. The PCE, VOC, JSC, and FF have shown 25.2 %, 0.718 V, 43.3 mA/cm2, and 80.8 %, respectively with reference structure's (Cu/FTO/CdS/Si/Au). The PCE, VOC, JSC, and FF have improved to 27.73 %, 0.74 V, 45.55 mA/cm2, and 79.94 %, respectively by adding FeSi2 layer as a bottom absorber with proposed structures (Cu/FTO/CdS/Si/FeSi2/Au). This research has the potential to offer insights and strategies for the development of cost-effective Si-based thin-film solar cells in a near future.

Improving the efficiency of a CIGS solar cell to above 31% with Sb2S3 as a new BSF: a numerical simulation approach by SCAPS-1D.

The remarkable performance of copper indium gallium selenide (CIGS)-based double heterojunction (DH) photovoltaic cells is presented in this work. To increase all photovoltaic performance parameters, in this investigation, a novel solar cell structure (FTO/SnS2/CIGS/Sb2S3/Ni) is explored by utilizing the SCAPS-1D simulation software. Thicknesses of the buffer, absorber and back surface field (BSF) layers, acceptor density, defect density, capacitance-voltage (C-V), interface defect density, rates of generation and recombination, operating temperature, current density, and quantum efficiency have been investigated for the proposed solar devices with and without BSF. The presence of the BSF layer significantly influences the device's performance parameters including short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE). After optimization, the simulation results of a conventional CIGS cell (FTO/SnS2/CIGS/Ni) have shown a PCE of 22.14% with Voc of 0.91 V, Jsc of 28.21 mA cm-2, and FF of 86.31. Conversely, the PCE is improved to 31.15% with Voc of 1.08 V, Jsc of 33.75 mA cm-2, and FF of 88.50 by introducing the Sb2S3 BSF in the structure of FTO/SnS2/CIGS/Sb2S3/Ni. These findings of the proposed CIGS-based double heterojunction (DH) solar cells offer an innovative method for realization of high-efficiency solar cells that are more promising than the previously reported traditional designs.

Design of a highly efficient n-CdS/p-AgGaTe2/p+-SnS double-heterojunction thin film solar cell

In this article, AgGaTe2-based n-CdS/p-AgGaTe2/p + -SnS double-heterojunction solar cells have been designed and explored utilizing a solar cell capacitance simulator (SCAPS-1D). This design manifested n-type CdS and p + -type SnS as window and back surface field (BSF) layer, respectively with the AgGaTe2 absorber. The major contributing parameters of these layers such as thickness, doping concentration level, and bulk flaws have been adjusted to reach the optimum computation. This introduced n-CdS/p-AgGaTe2/p + -SnS double-heterostructure solar cell demonstrates the significant power conversion efficiency (PCE) of 32.48% with the open circuit voltage, VOC of 0.96 V, short circuit current, JSC of 38.64 mA cm−2, and the Fill factor, FF of 87.31%. This remarkable efficiency is originated by the formation of a higher built-in potential at the p-AgGaTe2/p + -SnS heterostructure and a decrease in the surface recombination velocity brought on by the SnS BSF layer. This computational study demonstrates the potential of AgGaTe2 as an absorber and SnS as a BSF layer, and pave the way for the AgGaTe2-based experimental research in the era of solar cells.

Designing limiting-efficiency BaSi[formula omitted] solar cells by device simulation and computational material screening

A double heterojunction solar cell consisting of a solar absorber and electron/hole transport layers (ETL/HTL) is ideally efficient and can contribute to the exploitation of solar energy. BaSi2 is an attractive solar absorber material possessing a band gap of 1.3 eV and high absorption coefficients. However, finding proper ETL/HTL materials remains challenging. Here, limiting efficiency calculation, device simulation, and computational material screening are combined to design BaSi2 solar cells of near-limiting efficiency (> 28%). The limiting efficiency is calculated considering radiative and trap-assisted Auger recombinations, which shows that the Lambertian limit efficiency (32%) exceeds that of Si cells. Device simulations of double heterojunction BaSi2 cells were performed with different values of band gap, ionization potential, and electron affinity, which yields criteria for band-edge energy levels of the ETL and HTL. Candidate materials for the ETL and HTL are identified from the Materials Project database by three-step screening. The first step screens the materials for band gap, interface reactivity, lattice matching, etc. The second step is a literature survey to exclude air-sensitive or unstable materials under ambient conditions. In the third step, band-edge levels are calculated using density functional theory, and eight ETL and seven HTL candidate materials are identified. This device design method is applicable to any solar absorber material and promotes accelerated solar cell development.

InxGa1-xN/GaN double heterojunction solar cell optimization for high temperature operation

InxGa1-xN/GaN solar cells are ideal candidates for use in extreme temperature applications. The conversion efficiency potential of double heterostructure solar cells was investigated at high temperatures using physical simulation. For a targeted working temperature, optimized efficiency lies in a compromise between the absorber bandgap energy determined by In composition and the band offsets at the heterointerface directly correlated with the capability for the photogenerated carriers to cross through the barrier by thermoionic emission. An optimized efficiency of 18% is obtained for an In content of 50% at 400K and decreases down to 10% for an In content of 35% at 500K. As the operating temperature goes higher, the indium content needs to be reduced in order to limit the detrimental effect of increasing intrinsic carrier concentration. The consequence is a decreasing efficiency due to the reduced covered range of the solar spectrum. In the same time, the band offsets are no more a limiting parameter, as there are reduced as the In content decreases, and as higher temperature increases the thermionic transport probability. This result shows the interest of InxGa1-xN/GaN double heterostructure design for high temperatures applications.

Design and simulation of double-heterojunction solar cells based on Si and GaAs wafers

This article demonstrates the novel designs of Si and GaAs wafer-based double-heterojunction (DH) solar cells using SCAPS-1D simulator. Simple five-layer solar cells are proposed here: cells comprised of a cathode metal layer, three layers of semiconductor materials in the III–V, II–VI and group IV families--and a layer of anode metal. The device structures have been optimized for the analysis of the power-conversion efficiency (PCE) of the Si and GaAs solar cells considering high defect densities at and near each heterojunction. The PCEs predicted are 38% and 38.9% for n-ZnSe/p-Si/p +-Al0.8Ga0.2Sb and n-ZnSe/p-GaAs/p +-AlAs0.9Sb0.1 cells, respectively which stay entirely within the PCE limits set by the Shockley–Queisser theory of multi-junction cell. These results reveal that high efficiency and hence cost-effective Si and GaAs wafer-based DH solar cells can be fabricated in the near future.

Design guidelines for a highly efficient high-purity germanium (HPGe)-based double-heterojunction solar cell

Despite having higher carrier mobilities and absorption coefficients of germanium (Ge) than those of silicon (Si), there has been less focus on Ge-based solar cells due to the low bandgap and high cost of Ge wafer as well as the requirement of its high-purity level. Currently, the availability of high-purity Ge (HPGe), the low-cost wafer slicing method, and proper design guidelines make it possible to design HPGe-based solar cells. Accordingly, in this article, we have designed and simulated a novel n-CdS/p-HPGe/p+-BaSi2 based npp+ double-heterojunction solar cell (DHJSC), where HPGe, cadmium sulfide (CdS), and orthorhombic barium disilicide (β-BaSi2) have been used as the absorber, window, and back-surface field (BSF) layers, respectively. Using the solar cell capacitance simulator (SCAPS-1D), the effects of different physical parameters such as the thickness, doping, and defect densities, band offsets, and temperature on the photovoltaic (PV) parameters of the designed solar cells have been investigated systematically. This article renders the optimized PV parameters to improve the device performance with the highest power conversion efficiency (PCE) of ∼45.65% with a high open-circuit voltage of 1.16 V owing to the high built-in voltage of 1.7 V for the n-CdS/p-HPGe/p+-BaSi2 solar cells. This efficiency is almost consistent with the detailed balance limit for DHJSCs.

Simulative Parametric Study on Heterojunction Thin Film Solar Cells Incorporating Interfacial Nanoclusters Layer

Abstract Organic solar cells deal with small organic molecules for absorption of light at low cost and high efficiency. In this paper, we have analyzed the photovoltaic (PV) characteristics of double heterojunction solar cell that consists of copper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole (PTCBI) thin films. Here, CuPc and PTCBI layers are combined by an interfacial layer consisting of nanoscale dots. Different plasmonic materials (i. e. Ag, Au, and graphene) are selected as alternative nanoscale dot layer to examine their effect on solar cell performance. Further, the solar cell performance is also examined via variation in active layer thickness. The choice of interfacial layer material and variation in active layer thickness offer grounds for future efficient PV cells.

Room temperature H2 plasma treatment for enhanced passivation of silicon/TiO2 interface

Simultaneous requirement of excellent interface passivation and low thermal budget is a desirable feature for low cost Si based carrier selective solar cells. Accordingly, Titanium dioxide (TiO2), a widely used electron selective material, finds challenges related to thermal annealing like phase change and compatibility with thermal budget of hole transport layers. To address this, here we report a H2 plasma treatment process at room temperature which significantly reduces the surface recombination velocity (∼40 cm/s). Consequently, the reverse saturation current of the Si-TiO2 diode improves by a factor of 40, built-in potential improves by 100 mV, and the diode exhibits a near unity ideality factor. Using the same method, our Si-based double heterojunction solar cell results in an absolute increase of 2.4% in efficiency over devices with conventional thermal annealing. Given the ease of implementation and excellent performance, the proposed method is a promising alternative to thermal annealing for Si based heterojunction devices.

The Dawn of Lead-Free Perovskite Solar Cell: Highly Stable Double Perovskite Cs2AgBiBr6 Film.

Recently, lead‐free double perovskites have emerged as a promising environmentally friendly photovoltaic material for their intrinsic thermodynamic stability, appropriate bandgaps, small carrier effective masses, and low exciton binding energies. However, currently no solar cell based on these double perovskites has been reported, due to the challenge in film processing. Herein, a first lead‐free double perovskite planar heterojunction solar cell with a high quality Cs2AgBiBr6 film, fabricated by low‐pressure assisted solution processing under ambient conditions, is reported. The device presents a best power conversion efficiency of 1.44%. The preliminary efficiency and the high stability under ambient condition without encapsulation, together with the high film quality with simple processing, demonstrate promise for lead‐free perovskite solar cells.

Extraction of Front- and Rear-Interface Recombination in Silicon Double-Heterojunction Solar Cells by Reverse Bias Transients

We present a method, based upon reverse-recovery (RR) transient measurements, for determining the interface recombination parameters of double-sided heterojunction solar cells. A physics-based model is developed, and normalized parameters are used to provide results that can be scaled to arbitrary wafer thickness and minority-carrier diffusion coefficient. In the case of dominant recombination at only one interface, interface recombination velocity can be extracted directly from RR times. In devices with significant recombination at both interfaces, numerical modeling must be used. The effects of minority-carrier current spreading in small devices can be corrected for analytically. The results are then applied to both PEDOT/ n-Si and PEDOT/n-Si/TiO2 heterojunction cells. We find that the PEDOT/n-Si interface, despite favorable band offsets and a significant built-in voltage, is not an ideal hole injector because of recombination at the PEDOT/n-Si interface. We also find that the effective surface recombination velocity at the Si-TiO2 interface in a metallized device is 330 cm/s, confirming that the interface has a low defect density. Finally, we reflect on the significance of these results for the further development of silicon heterojunction cells.

Designs for Donor–Acceptor Copolymer-Based Double Heterojunction Solar Cells

Self-consistent field calculations were used to examine a design motif for organic double heterojunction solar cell materials. They are a specific type of cascade heterojunction designed to increase cell voltage without sacrificing current and consist of fully conjugated block polymers. The design employs three sections: a p-type section, an n-type section, and a third section called the bridge. The energy alignment between sections is important to optimal device function, and a motif based on electron-donating and electron-accepting subunits was evaluated. If the energetic offset between p-type and n-type sections is greater than the exciton binding energy and if the bridge is formed using the scheme presented, a nearly ideal energetic alignment is obtained. In addition, calculations on the excited states of the system were performed to illustrate the relationship between bridge length and the magnitude of charge carrier recombination currents. An order of magnitude decrease relative to the corresponding...

Effects of structural defects and polarization charges in InGaN-based double-junction solar cell

The performance of a double heterojunction solar cell based on Indium Gallium Nitride (InGaN) including a tunnel junction was simulated. The most challenging aspects of InGaN solar cells development being the crystal polarization and structural defects detrimental effects, their impact on the solar cell performances has been investigated in detail. The solar cell simulation was performed using physical models and InGaN parameters extracted from experimental measurements. The optimum efficiency of the heterojunction solar cell was obtained using a multivariate optimization method which allows to simultaneously optimize eleven parameters. The optimum defect free efficiency obtained is 24.4% with a short circuit current JSC=12.92mA/cm2, an open circuit voltage VOC=2.29V and a fill factor FF=82.55%. The performances evolution as functions of the polarization and the defects types and parameters was studied from their maximum down to as low as a 2% efficiency.

III-Nitride Double-Heterojunction Solar Cells With High In-Content InGaN Absorbing Layers: Comparison of Large-Area and Small-Area Devices

This paper investigates the molecular beam epitaxy (MBE) growth, material characterization, and performance testing of indium gallium nitride (InGaN)/GaN double-heterojunction solar cells. Structures with varying thicknesses and compositions of the InGaN absorbing layer are studied. The N-rich MBE growth at low temperatures enables the growth of thick 10% and 20% InGaN films with minimal strain relaxation and defect generation. The characteristics of both large- and small-area devices are compared. While leakage current and high ideality factors associated with the double-heterojunction structure remain issues as detected by I–V and concentration effect measurements, the double-heterojunction cell with a record-high In content of 22% shows a promising photovoltaic response.

Solution-processed crystalline silicon double-heterojunction solar cells

Crystalline silicon double-heterojunction solar cells were fabricated using Si/organic and Si/Cs2CO3 heterojunctions. The front heterojunction is formed by spin-coating conductive polymer poly(3,4-ethyenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) on n-type Czochralski (CZ) (100) silicon, which separates the photogenerated carriers and blocks the electron dark current while allowing the photocurrent to pass through. The rear heterojunction, formed by spin-coating Cs2CO3 and polyethylenimine (PEI) dissolved in 2-ethoxyethanol and Al metal evaporation, functions as a back surface field that reduces the hole dark current while allowing the electron photocurrent to pass through. The double-heterojunction device showed a power conversion efficiency of 12.7% under AM1.5G simulated solar light exposure.

Simulation of InGaN p–i–n double heterojunction solar cells with linearly graded layers

This paper deals with theoretical investigation of the performance of nonpolar InGaN double heterojunction solar cell. Inserting linearly graded layers at the interface between the p-GaN/i-InGaN and i-InGaN/n-GaN is shown to remove the barrier for electron and hole transport into GaN and increases the cell efficiency. The proposed structure is simulated using 1D finite element method. The influence of the graded layer thickness on the conversion efficiency is particularly investigated. The results show that the efficiency can be optimized by choosing an appropriate graded layer thickness. Simulations predict a conversion efficiency of about 24% for a graded layer thickness of 0.15μm.

Optimization of p-GaN/InGaN/n-GaN Double Heterojunction p-i-n Solar Cell for High Efficiency: Simulation Approach

We have conducted numerical simulation of p-GaN/In0.12Ga0.88N/n-GaN, p-i-n double heterojunction solar cell. The doping density, individual layer thickness, and contact pattern of the device are investigated under solar irradiance of AM1.5 for optimized performance of solar cell. The optimized solar cell characteristic parameters for cell area of 1 × 1 mm2are open circuit voltage of 2.26 V, short circuit current density of 3.31 mA/cm2, fill factor of 84.6%, and efficiency of 6.43% with interdigitated grid pattern.

INFLUENCES OF ASYMMETRICALLY DISTRIBUTED DEFECT STATES AT REAR c-Si/a-Si:H INTERFACE ON PERFORMANCES OF SILICON HETERO-JUNCTION SOLAR CELLS

The performances of silicon double hetero-junction solar cells are investigated by the numerical simulator "Automat For Simulation of Hetero-structures (AFORS-HET)". Asymmetrical distribution of acceptor and donor defect states at the rear hetero-junction interface is introduced in both a-Si:H(n)/c-Si(p)/a-Si:H(p+) and a-Si:H(p)/c-Si(n)/a-Si:H(n+) structures in our study. The influences of total defect density and rear emitter parameters (doping concentration and band discontinuity to silicon substrate) on performances of the solar cells are analyzed. The simulated results indicate that the npp + cells with acceptor dominated defect states at the rear interface can obtain better performances, and the same for the pnn + cells with donor dominated defect states. Moreover, the npp + cells are more sensitive to the total interface defect density and its distribution mode due to the unfavorable band offset between the absorber and the rear emitter. But when total defect density is small, the npp + cells show more sensitivity to change of the doping concentration at the rear emitter than the pnn + cells, and conversely, the pnn + cells show more sensitivity to the distribution mode of defect states at the rear emitter than the npp + cells. Due to weaker inherent back diffusion ability of minority carrier, the pnn + cells with moderate band offset (0.25 ~ 0.37 eV ) at the rear hetero-junction are more sensitive to the incentive effect of localized charges at the interface formed by asymmetrically distributed defect states, and the interface with donor dominated defect states is a better option for the pnn + cells when the total defect density is relatively small.

Electronic structure effect of polythiophene derivatives and nano N-Zn-Ag/TiO2 on performance of organic thin film solar cell

Nanocrystal N-Zn-Ag/TiO2 powders were prepared with N-Zn/TiO2 by photo deposition method. A series of pure polymers P3HT[poly(3-hexylthiophene)], P3OT[poly(3-octylthiophene)], P3DT[poly(3-decylthiophene)] and P3DDT[poly(3-dodecylthiophene)], was synthesized, which were used to synthesize p-n type semiconductor materials P3HT/N-Zn-Ag-TiO2, P3OT/N-Zn-Ag-TiO2, P3DT/N-Zn-Ag-TiO2 and P3DDT/N-Zn-Ag-TiO2 by in situ chemical method. X-Ray diffraction(XRD) and infrared(IR) spectroscopy showed the structure of the polymers and complexes. Ultraviolet-visible(UV-Vis) spectra and cyclic voltammograms(CV) showed the optical and electronic performance of the polymers and complexes. Two new single and double organic thin film heterojunction solar cells were prepared with the above mentioned synthesized powders as raw materials. Current-voltage(I–V) measurements indicate that the conversion efficiency of the single organic thin film heterojunction solar cell is higher than that of the double organic thin film heterojunction solar cells. Single organic thin film heterojunction solar cells based on P3DT/N-Zn-Ag-TiO2 can get a photoelectric conversion efficiency of 0.0408%. The performance of electronic transform between electron donor and acceptor on organic thin film solar cells was researched.