CIGSSe Solar Cells Research Articles

Cesium Modulation in Cu(In, Ga)(S, Se)2 Solar Cells: Comprehensive Analysis on Interface, Surface, and Grain Boundary.

Cesium (Cs) incorporation and sulfurization on copper indium gallium selenide solar cells are the keys to improving the device quality. In this study, we explore the impact of Cs modulation on sulfur-containing Cu(In, Ga)(S, Se)2 (CIGSSe) absorbers, resulting in a performance increase of over 2%, reaching 18.11%. The improvement stems from a widened surface bandgap, grain boundary (GB) passivation, and a moderate injection blocking layer. The surface bandgap widens from 1.44 to 2.63 eV after Cs incorporation, confirmed by ultraviolet photoelectron spectroscopy (UPS) and low-energy inverse photoemission spectroscopy (LEIPS) analysis. Cs presence and S depletion in GBs suggest a new phase that might mitigate carrier recombination. Heightened Cs incorporation introduces interface issues, including an augmented injection blocking layer and interface defects. Our study offers insights into interface challenges and GB engineering strategies in Cs-treated CIGSSe solar cells, illuminating the multifaceted impact of heavy alkali metal ion Cs in CIGS-based photovoltaics.

Solution‐Processed Bifacial Cu(In, Ga)(S, Se)2 Thin‐Film Solar Cells with a Frontside Power Efficiency of 9.73%

Cu(In, Ga)(S, Se)2 (CIGSSe) solar cell is one of the most promising thin‐film solar cells with a record power conversion efficiency (PCE) of 23.6%. Conventional CIGSSe thin‐film solar cells are usually fabricated on Mo‐coated soda‐lime glass substrate, thereby, the sunlight on the rear side cannot be utilized by the monofacial CIGSSe solar cells owing to the opacity of the Mo electrode. CIGSSe solar cells fabricated on transparent conductive oxide (TCO) electrode enable to fabricate bifacial solar cells, which can generate power on both sides of solar cells, so that bifacial solar cells have a high potential application in building‐integrated photovoltaics. However, the PCEs of CIGSSe solar cells fabricated on TCO substrates are significantly lower than those of ones on Mo substrates. In this article, bifacial CIGSSe solar cells on fluorine‐doped tin oxide (FTO) substrate are fabricated by using an ionic liquid‐assisted solution approach and utilizing a MoO3 thin film as an interface layer between FTO and CIGSSe absorber layer, yielding a front‐side PCE of 9.73% and a back‐side PCE of 1.77%.

Development of CeMnO2 and CeMnO2 buffer layer nanomaterials for CIGSSe/perovskite double-graded solar cells

Solar cells are a popular sustainable power source, but their electrical characteristics deteriorate over time due to a lack of UV light absorbent and wide energy bandgap buffer layer materials. Photon collecting in the UV wavelength band remains a difficult problem for making high-performance CIGSSe solar cells. Recently, several researchers have used CdS, Zn (O, S), ZnMnO, and ZnMgO buffer layer materials for making a CIGSSe solar cell. However, these buffer layers have various drawbacks, including a smaller energy bandgap, lower UV light absorption, and heavy metal toxicity. To solve the above problems, we used CeMnO2 buffer-1 and CeMgO2 buffer-2 as hole-reflected layer nanomaterials to create a high-efficiency CIGSSe/perovskite double-graded photovoltaic cell. The materials have a wide energy bandgap, high UV light absorption, and are toxic-free. First, we synthesized and characterized the CeMnO2 and CeMgO2 buffer layer materials; later, we used the extracted optical and electrical properties of both buffer layer nanomaterials to model a proposed high-efficiency solar cell numerically. X-ray diffraction (XRD) and scanning electron microscope (SEM) instruments have been used to confirm the average crystallite size, hexagonal cubic fluorite-like structure, surface characteristics, average particle size, and CeMnO2 and CeMgO2 nanomaterial morphology. The optical and electrical properties of both buffer layer materials are determined using ultraviolet–visible (UV–Vis) spectrophotometry and Hall Effect measurements. The study proposes a high-efficiency (SLG/Al/ZnMgO:Al/CeMnO2/CeMgO2/CIGSSe/MAFPbBrI/Mo) inorganic and organic solar cell using experimental data of CeMnO2 and CeMgO2 buffer layer nanomaterials. The bandgap energy increases from 3.68 to 3.86 eV for the CeMnO2 buffer-1 layer and from 3.578 to 3.865 eV for the CeMgO2 buffer-2 layer, and the device enhances photovoltaic characteristics, with an efficiency of 29.68 %, JSC of 39.37 mA/cm2, VOC of 873.9 mV, and FF of 86.28.

Flexible and lightweight Cu(In,Ga)(S,Se)2 solar cell on a stainless steel substrate with different structures for improving band alignment

Herein, the conduction band minimum (EC) difference between the absorbing and buffer layers (named CBO) and that between the absorbing layer and the transparent conductive oxide (named ΔEC-TA) for the total band alignment of flexible and lightweight Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells on a stainless steel (SS) substrate with different structures were measured and optimized to improve their photovoltaic performances. Under different structures, the first buffer layers are Zn(O,S,OH)x, CdS, and (Cd,Zn)S, the second buffer layer is Zn0.84Mg0.16O, and the transparent conductive oxide (TCO) layer is Zn0.88Mg0.12O:Al, leading to different CBO and ΔEC-TA values. According to theoretical and experimental examinations, the replacement of ZnO:B TCO by Zn0.84Mg0.16O buffer/Zn0.88Mg0.12O:Al TCO results in the improvement of band bending (reduced carrier recombination) in the device, which is attributed to EC values of Zn0.84Mg0.16O buffer/Zn0.88Mg0.12O:Al TCO being shallower than that of ZnO:B, thus improving ΔEC-TA. Moreover, the Zn(O,S,OH)x and (Cd,Zn)S buffers give rise to the improved CBO in the device. Ultimately, experimental conversion efficiency of 18.1% for the flexible and lightweight CIGSSe solar cell on the SS substrate was obtained through the use of (Cd,Zn)S as the first buffer, Zn0.84Mg0.16O as the second buffer, and Zn0.84Mg0.16O, Zn0.88Mg0.12O:Al as the TCO layer, leading to the optimized CBO value of −0.01 eV and ΔEC-TA value of +0.16 eV, which reduced carrier recombination; this was well verified by the predicted numerical result.

Rear Interface Engineering in Solution‐Processed Submicron Cu(In,Ga)(S,Se)2 Solar Cells on Transparent Sn:In2O3 Back Contact

AbstractThe parasitic absorption in Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells emerging from the Mo back contact can be significantly reduced by replacing it with tin‐doped indium oxide (ITO). Commonly, an undesirable GaOx layer forms at the CIGSSe/ITO interface during the high‐temperature fabrication process, which has a detrimental effect on photo‐carrier extraction. Here, a Cu‐In‐TU‐DMF (TU: thiourea, DMF: N, N‐Dimethylformamide) intermediate layer for modification of the CIGSSe/ITO interface, which improves the efficiency of submicron CIGSSe solar cells significantly, is reported about. The reference submicron CIGSSe solar cells exhibit inferior performance (2.4% efficiency) and a large open circuit voltage deficit (Voc,def = 815.9 mV) due to a high barrier at the CIGSSe/ITO interface. At the modified rear interface, the recombination is reduced and hence carrier transport and collection are obviously improved. The efficiency of submicron CIGSSe solar cells on ITO with rear interface modification achieves 7.9% with an open circuit voltage of 565.8 mV, a short circuit current density of 23.4 mA cm−2, and a fill factor of 59.5%, as well as a Voc,def of 589.2 mV.

Inkjet‐Printed Cu(In,Ga)(S,Se)2 Thin Film Solar Cells Exceeding 15% Power Conversion Efficiency

Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells are one of the most promising thin film photovoltaics with a record efficiency of 23.6%. However, the biggest drawback to CIGSSe solar cells is their high material cost, partially resulting from relatively rare and expensive indium and gallium. Therefore, improving the utilization of indium and gallium and reducing their wastage can greatly lower the cost of CIGSSe thin film solar cells. Inkjet printing is a facile, cost‐effective, and low‐waste deposition technology, which is particularly suitable for low‐cost and large‐area fabrication of CIGSSe solar cells. Herein, a novel and green ionic liquid‐assisted ink to fabricate highly efficient CIGSSe solar cells is developed. The material utilization of inkjet printing can be remarkably improved compared to the conventional vacuum‐based deposition approach and spin‐coating solution approach. The CIGS printable ink is prepared by dissolving copper acetate, indium acetate, gallium nitrate, and thiourea into ethanol with the assistance of n‐butylammonium butyrate ionic liquid. Ionic liquid‐assisted CIGS ink has a nearly zero wetting angle and a tunable viscosity, which enable to deposit a flat and continuous CIGS thin film by an inkjet printing method. An encouraging power conversion efficiency of 15.22% has been achieved for inkjet‐printed CIGSSe solar cells.

The impact of SnMnO2 TCO and Cu2O as a hole transport layer on CIGSSe solar cell performance improvement

The impact of SnMnO2 TCO and Cu2O as a hole transport layer on CIGSSe solar cell performance improvement

Efficiency Improvement of Narrow Band Gap Cu(In,Ga)(S,Se)2 Solar Cell with Alkali Treatment via Aqueous Spray Pyrolysis Deposition

The chalcopyrite Cu(In,Ga)(S,Se)2 (CIGSSe) solar cell with a low band gap is a promising candidate for use as the bottom cell in high-efficiency tandem solar cells. In this study, we investigated narrow band gap CIGSSe solar cells, both with and without alkali treatment. The CIGSSe absorbers were fabricated using aqueous spray pyrolysis in an air environment, with the precursor solution prepared by dissolving constituent metal salts. We found that the power conversion efficiency (PCE) of the fabricated solar cell was significantly enhanced when rubidium postdeposition treatment (PDT) was applied to the CIGSSe absorber. The Rb-PDT facilitates defect passivation and a downshift of the valence band maximum of the CIGSSe absorber, thereby improving the power conversion efficiency and all device parameters. Due to these beneficial effects, a PCE of ∼15% was obtained with an energy band gap of less than 1.1 eV, making it suitable for use as the bottom cell in a highly efficient tandem solar cell.

Influences of Mg concentration in ZnMgO film on energy band alignment at CIGSSe/Zn1-xMgxO interface and performances of CIGSSe solar cells

Zn1-xMgxO buffered CdS free CIGSSe solar cell has been believed to be a new simplified structure solar cell with great potential. ZnMgO film plays an important role. To obtain a high quality Zn1-xMgxO thin film becomes a key issue. In this work, Zn1-xMgxO films with different Mg concentrations were prepared by magnetron co-sputtering, and physical performances of Zn1-xMgxO films were investigated. Meanwhile, CdS free CIGSSe solar cells were prepared based on Zn1-xMgxO buffer layers. The effects of Mg concentration in Zn1-xMgxO buffer layers on device performances, energy band alignment, and interface recombination of CIGSSe solar cells were studied. The results show that although the doping of Mg reduces the crystallinity of Zn1-xMgxO films, it increases the band gap by increasing the conduction band minimum. In Zn1-xMgxO buffered CdS free CIGSSe solar cells by all-sputtering process, the photoelectric conversion efficiency increases first and then decreases with the increase of Mg concentration in the x range from 0 to 0.3, which is mainly attributed to the changes of FF and VOC. Meanwhile, the change of Mg concentration affects the energy band alignment at the CIGSSe/Zn1-xMgxO interfaces. The highest efficiency of 15.2 % of Zn0.8Mg0.2O buffered CdS free CIGSSe solar cell with the energy band difference of 0.27 eV was obtained in this work.

High Efficiency Aqueous Solution Sprayed CIGSSe Solar Cells: Effects of Zr4+‐Alloyed In2S3 Buffer and K‐Alloyed CIGSSe Absorber

AbstractEven though solution‐processed Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells have been developed for long time, their power conversion efficiency (PCE) is still much behind that achieved by vacuum‐based process, and some solvents used in solution‐based processes are not environmental friendly. High‐efficiency CIGSSe solar cells made by using water‐based spray deposition in an air environment are reported. Water is the most eco‐friendly and cheapest solvent compared to the other solvents used in solution‐based fabrication. In2S3‐based buffer (eco‐friendly Cd‐free buffer) and CdS buffer are tested as a buffer layer. For higher PCE with In2S3‐based buffer, a Zr4+‐alloyed In2S3 is used and Zr4+ alloying effects are investigated. It is found that Zr4+ alloying increases the electron concentration in the buffer and passivates defect states in the CIGSSe absorber, which enhance PCE significantly. On the other hand, it is found that K‐alloying into the CIGSSe absorber passivates defects in the CIGSSe absorber, which further increases PCE. Owing to the observed beneficial effects, highest PCE of 16.08% and 17.74% is achieved with Zr4+‐In2S3 buffer and CdS buffer, respectively. In addition, since fabricated solar cells are made with bandgap below 1.15 eV, they can be utilized as a bottom cell for high efficiency tandem cell.

Total band alignment in theoretical and experimental aspects for enhanced performance of flexible and Cd‐free Cu (In,Ga)(S,Se)2 solar cell fabricated by all‐dry process

AbstractTotal band alignment parameters, which are CBO, ΔEC‐TA, and ΔEC‐TB values, in the Cu (In,Ga)(S,Se)2 (CIGSSe) solar cells are theoretically and experimentally optimized. Conduction band minimum (EC) difference between the CIGSSe absorber and buffer is represented by CBO, and that between absorber and transparent conductive oxide (TCO) is denoted by ΔEC‐TA. The EC difference between buffer and TCO is represented by ΔEC‐TA. Based on the measurement of photoelectron yield spectroscopy, the actual CBO, ΔEC‐TA, and ΔEC‐TB values are disclosed. According to the numerical simulation, the useful overview information about the appropriate CBO, ΔEC‐TA, and ΔEC‐TB values is disclosed for the selections of the suitable buffer and TCO materials to reduce the carrier recombination, thus enhancing the photovoltaic performances of the CIGSSe solar cell. As a result, the sputtered Zn0.84Mg0.16O buffer and sputtered Zn0.88Mg0.12O:Al TCO layers are experimentally applied for the appropriate CBO of +0.11 eV, ΔEC‐TA of +0.16 eV, and ΔEC‐TB of +0.05 eV, thus giving rise to the flexible, Cd‐free, and all‐dry process CIGSSe solar cell on stainless steel substrate with the increased conversion efficiency up to 15.3% (and the highest one of 16.5%) as the eco‐friendly and low‐cost solar cell. It is ultimately suggested that the experimental results are well predicted by the overview numerical results, which are useful for the improvement of the photovoltaic performances through the total band alignment.

Influence of SnMnO2 window layer on enhancing the performance of CIGSSe thin-film solar cell

In this paper, the thickness and doping concentrations of the double buffer cell-based conventional CIGSSe solar cells are optimized, and alignment of the energy band of the optimized solar cell (ZnMgO/CIGSSe) is carried out, thus obtaining an increase in efficiency from 23.35 % to 27.88 %. Further, a new design is proposed of low cost, low resistivity, minimum absorption coefficient, tunable energy bandgap (3.6–4.44 eV) with tin-doped manganese oxide Sn1−xMnxO2 material (x = 0.5) as a window layer in conventional solar cell design. The thin-film solar cell efficiency has improved from 23.35 % to 29.05 % by aligning the energy bandgap with an optimized thickness and doping concentration. The proposed Sn1−xMnxO2 window layer-based thin-film solar cell is more convenient in instantly absorbing the maximum blue light with reduced recombination loss, increased efficiency and external quantum efficiency. The simulated parameters of the conventional model are compared and validated with the existing conventional solar cells.

Position Influence of Sputtered Zn1-xMgxO/Zn1-xMgxO:Al Layers in Flexible and Cd-Free Cu(In,Ga)(S,Se)2 Solar Cells.

Flexible, Cd-free, and all-dry process Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells on stainless steel (SUS) substrates are fabricated, and their structure consists of SUS/glass (SiO2)/Mo/CIGSSe absorber/sputtered Zn0.84Mg0.16O/sputtered Zn1-xMgxO:Al transparent conductive oxide (TCO). The effect of the sample position during the sputtering of Zn0.84Mg0.16O buffer and Zn1-xMgxO:Al TCO layers of the solar cells is examined to avoid intense plasma exposure. The sample position plays a vital role in improving the cell performance. Namely, the sample position close to the material targets of the sputtering system causes severe exposure of the sample to the intense plasma, giving rise to low and nonuniform local external quantum efficiency (EQE) with very weak electroluminescence (EL) imaging, thereby reducing photovoltaic performance. On the other hand, the deviation of the sample position from material targets helps to avoid the intense plasma, thus resulting in high and uniform local EQE with bright EL imaging as well as reducing carrier recombination rates (or carrier lifetimes) throughout the solar cells. Ultimately, the conversion efficiency of flexible, Cd-free, and all-dry process CIGSSe solar cells is enhanced to 16.5% under the optimized sample position deviation from material targets to avoid intense plasma exposure.

Fabrication of in situ alkali doped flexible CIGSSe solar cells by using aqueous spray deposition

Flexible Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells were fabricated on stainless steel foil by using aqueous spray deposition method. Since stainless steel foil is used, external alkali doping is necessary to passivate defects in CIGSSe absorber. We investigated effects of (Na, K) co-doping and selenization temperature on solar cell performance. With co-doping of Na and K, defect states were passivated significantly and highest power conversion efficiency (PCE) was obtained. However, at higher K concentration of more than 0.5%, different growth mode of CIGSSe was observed and deep defect states were developed, decreasing PCE. In addition, selenization temperature effects were studied by varying selenization temperatures. With higher selenization temperature, defect passivation for the CIGSSe absorber was more apparent, which facilitated increase of open circuit voltage. However, short circuit current was observed to be decreased at higher selenization temperature of 570 °C. This work demonstrates in-situ alkali co-doping into CIGSSe absorber with simple and low-cost spray deposition in an air environment.

Over 12% Efficient CuIn(S,Se)2 Solar Cell with the Absorber Fabricated from Dimethylformamide Solution by Doctor‐Blading in Ambient Air

Solution‐processed chalcopyrite copper indium gallium sulfoselenide (Cu(In,Ga)(S,Se)2, CIGSSe) thin‐film solar cells have achieved efficiency beyond 18% and have great potential as an alternative to vacuum‐based ones. However, most of the efficient solution‐based CIGSSe solar cells are fabricated by spin‐coating in an inert atmosphere, which limits the transfer from lab protocol to industrial large‐scale production. Herein, a scalable doctor‐blading technique is applied to fabricate CuIn(S,Se)2 (CISSe) absorbers from N,N‐dimethylformamide molecular precursor solution in ambient air. With the optimization of the precursor concentration to reduce the residue solvent and change the thermal annealing process from one‐step to two‐step to separate solvent evaporation and complex decomposition to suppress fluidity, high‐quality absorber films with densely packed large grains have been fabricated and a champion CISSe solar cell with a power conversion efficiency of 12.54% has been achieved. Importantly, unlike the spin‐coating technique which may cause composition change due to the different solubilities of the precursors, the doctor‐bladed film has a composition very close to the precursor solution, which is very important for precise control of the absorber composition for industrial production.

Study on the Performance of Oxygen-Rich Zn(O,S) Buffers Fabricated by Sputtering Deposition and Zn(O,S)/Cu(In,Ga)(S,Se)2 Interfaces

We developed a novel process for fabricating oxygen-rich Zn(O,S) buffer layers by magnetron reactive sputtering with a single oxygen-rich Zn(O,S) target, suitable for industrial all-dry production. Then, we successfully fabricated Cd-free Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells. By varying the oxygen partial pressure during sputtering from 0 to 20%, we precisely controlled the Zn(O,S) composition, then systematically investigated its effects on the quality of oxygen-rich Zn(O,S) films, the properties of formed p-n junctions, and the performance of CIGSSe solar cells with Zn(O,S) buffer. We demonstrated that reactive sputtering with a Zn(O,S) target can generate a homogeneous, high-quality oxygen-rich Zn(O,S) buffer on large-area substrates. We observed a unique and unusual phenomenon: the appropriate content of secondary phase ZnSO4 and ZnSO3 improved the band alignment for oxygen-rich Zn(O,S). Combining our proposed schematic diagram of band alignmentat the Zn(O,S)/CIGSSe interface, we established a crucial correlation between the device performance and the interfacial properties at the p-n junction. For the CIGSSe device performance, the band alignment matching at the heterojunction plays a primary role, and the quality of oxygen-rich Zn(O,S) films plays a secondary role. Consequently, an excellent oxygen-rich Zn(O,S) buffer can be obtained with 10% Zn(O,S) deposition oxygen partial pressure , and the optimized device shows a higher Voc (447 mV) and a similar conversion efficiency (11.2%) than conventional CIGSSe devices with CdS buffer.

Formation of Native Inx(O,S)y Buffer through Surface Oxidation of Cu(In,Ga)(S,Se)2 Absorber for Significantly Enhanced Conversion Efficiency of Flexible and Cd‐Free Solar Cell by All‐Dry Process

Herein, flexible, Cd‐free, and all‐dry process Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells on stainless steel (SUS) substrates are developed with manufacturing CIGSSe absorbers fabricated in real production line with large sample size of 0.94 × 1.23 m2. Air‐annealing process under a temperature of 130 °C, 1 atmospheric pressure, and air humidity of about 50% (accelerated oxidizing process) is conducted on absorbers for their oxidized surface. It is demonstrated for the first time that oxidized surface of CIGSSe absorbers after air‐annealing process gives rise to considerable increases in photovoltaic performances of CIGSSe solar cells. This occurs because of formation of native Inx(O,S)y buffer near CIGSSe surface formed after air‐annealing process, which yields self‐forming heterojunction, acting as charge separation and hole‐blocking barrier with increased valence band offset of native Inx(O,S)y/CIGSSe to 1.4 eV, thereby avoiding sputtering damage on CIGSSe surface. Therefore, carrier recombination rates at the interface and depletion regions of the solar cell are reduced, implying improvement of interface and near‐surface qualities. Ultimately, conversion efficiency of 16.7% for flexible, Cd‐free, and all‐dry process CIGSSe solar cell on SUS substrate is attained after the air‐annealing process (130 °C and 6 h) with potential toward Lab‐to‐Fab transition.

Exfoliation methods for compositional and electronic characterization of interfacial Mo(Sex,Sy) in Cu(In,Ga)(Se,S)2 solar cells by X‐ray and UV photoelectron spectroscopy

Mo(SexSy) is a transition metal dichalcogenide typically applied as a back contact interlayer in Cu(In,Ga)(Se,S)2 (CIGSSe) solar cells. Band alignment at the buried Mo/CIGSSe junction mediated by Mo(SexSy) is important for current transport and enables quasi‐ohmic behavior between the CIGSSe absorber and the Mo back electrode. Furthermore, the S/(Se + S) ratio is a crucial parameter that determines the height of the valence band offset at the CIGSSe/Mo(SexSy) interface. Because the interlayer is formed during rapid thermal processing, an MoSe2 or MoS2 thin film grown on free substrate surfaces will not be representative for a realistic solar cell device. Thus, for fundamental thin‐film material analysis, as well as functional characterization and modeling, appropriate preparation and analytical techniques are required in order to prevent artifacts. In principal, the weak van der Waals forces between two‐dimensional stacked Mo(SexSy) sheets allow the implementation of exfoliation procedures to generate free Mo(SexSy) surfaces out of CIGSSe solar cell layer stacks. In this article, two different exfoliation‐based Mo(Sex,Sy) preparation methods are investigated and evaluated with respect to subsequent surface analytical characterization by X‐ray and ultraviolet photoelectron spectroscopy. A special focus is laid on an artifact‐free characterization of chemical and electronical properties of the exposed layers for a number of samples. In a first instance, the compositional Se/S and (Se + S)/Mo ratios at the surface are quantitatively analyzed on the basis of dedicated peak‐fitting routines. Artifacts from carbonaceous contamination due to different exfoliation glues can be prevented through a detailed comparative analysis of carbon 1s and KLL Auger peaks. Furthermore, a significant surface band bending is observed that can be reduced by low‐energy Ar ion in situ sputtering. A simple model for the sputter removal of a charged surface layer is presented, which allows to approximately calculate the absolute valence band maximum (VBM) positions required for band alignment and numerical device simulations. The presented exfoliation surface analysis methodology is important for the whole CIGS(Se) solar cell community and may be of general interest for emerging applications of further 2D transition metal dichalcogenides as well.

Identifying dominant recombination locations in double‐graded Cu(In1‐xGax)(Se1‐ySy)2 solar cells and their impact on the performance at different light intensities

AbstractIn this work, the impact of different Cu(In1‐xGax)(Se1‐ySy)2 solar cell structures on the shift of the dominant recombination region at varying light intensities was investigated. A new parameter was proposed to account for the dominant recombination region relative to the minimum band gap location in a graded absorber. Additionally, the influence of shunt resistances on the dominant recombination location for different CIGSSe solar cell structures was modeled. Within the investigated illumination range, correlations between the dominant recombination location and solar cell parameters as well as their temperature dependence were discussed.

Defects passivation and crystal growth promotion by solution-processed K doping strategy toward 16.02% efficiency Cu(In,Ga)(S,Se)2 solar cells

Unsatisfactory crystal quality and deep-level defects are detrimental for Cu(In,Ga)(S,Se)2 (CIGSSe) solar cells. In this work, an in-suit K doping strategy is implemented by introducing KF into the CIGSSe precursor solution to promote crystallization and passivate the deep defects. The effects of K on the solution-processed CIGSSe devices are systematic investigated. It has been discovered that K incorporation results in better crystallization, modified CIGSSe surface and fewer detrimental defects. Benefit from the reduction of the band-tailing effects, suppressed defects density and passivated interface recombination, the solution-processed CIGSSe solar cell achieve systematic improvement in open-circuit voltage and fill factor, enabling a champion efficiency of 16.02%, which is the highest value for alkali metal doped CIGSSe solar cells fabricated by solution-processed method. The effective in-suit K doping tactic opens an avenue for developing highly efficient solution-processed CIGSSe solar cells.