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The fox and the hound: in-depth and in-grain Na doping and Ga grading in Cu(In,Ga)Se <sub/>2</sub> solar cells
摘要： Cu(In,Ga)(S,Se)2 (CIGS) thin film solar cells require appropriate depth and lateral distributions of alkali metal dopants and gallium to attain world record photovoltaic energy conversion. The two requirements are interdependent because sodium is known to hamper In/Ga interdiffusion in polycrystalline films. However, such a fact is challenged by recent findings where sodium appears to enhance In/Ga interdiffusion in monocrystalline films. This contribution reviews closely the two cases to the benefits of grain boundary engineering in CIGS. A computational model reveals why Na induces In accumulation at CIGS grain boundaries, confining Ga to grain interiors. The positive technological implications for wider gap chalcopyrites are stressed.
关键词： sodium doping,gallium grading,CIGS,solar cells,grain boundary engineering
更新于2025-09-23 15:21:01
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Surface passivation and point-defect control in Cu(In,Ga)Se <sub/>2</sub> films with a Na <sub/>2</sub> S post deposition treatment for higher than 19% CIGS cell performance
摘要： Na2S as a new alkaline source was employed to passivate the surface of CIGS film. Na2S has less formation enthalpy compared to alkali fluoride compounds leading to the more effective dissolution at the surface. An efficiency of 19.2% was obtained by post deposition treatment (PDT) with Na2S source for cell with anti-reflective coating and active area of a 0.43cm2. The remarkable performance enhancement compared to the efficiency of 16.64% of the cell without the PDT was due to the increase of Voc and FF. With the Na2S PDT, Na distribution in CIGS film was much shallower and the valence band lowering was smaller compared to that with NaF PDT. The emission intensity of low-temperature photoluminescence at 1.04 eV, which corresponds to electron transition from In-in-Cu (InCu) antisite to the valence band maximum, was greatly reduced by Na2S PDT compared to NaF PDT. The result suggests that in addition to lowering the Cu vacancy concentration, the concentration of InCu defects significantly decreased at the CIGS surface by Na2S PDT compared to NaF PDT. Our results indicated that the surface passivation by Na2S PDT was more effective than NaF PDT.
关键词： point defects,Na2S source,CIGS solar cells,surface passivation,post-deposition treatment (PDT)
更新于2025-09-19 17:15:36
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Rear‐Passivated Ultrathin Cu(In,Ga)Se <sub/>2</sub> Films by Al <sub/>2</sub> O <sub/>3</sub> Nanostructures Using Glancing Angle Deposition Toward Photovoltaic Devices with Enhanced Efficiency
摘要： In this work, for the first time, the addition of aluminum oxide nanostructures (Al2O3 NSs) grown by glancing angle deposition (GLAD) is investigated on an ultrathin Cu(In,Ga)Se2 device (400 nm) fabricated using a sequential process, i.e., post-selenization of the metallic precursor layer. The most striking observation to emerge from this study is the alleviation of phase separation after adding the Al2O3 NSs with improved Se diffusion into the non-uniformed metallic precursor due to the surface roughness resulting from the Al2O3 NSs. In addition, the raised Na concentration at the rear surface can be attributed to the increased diffusion of Na ion facilitated by Al2O3 NSs. The coverage and thickness of the Al2O3 NSs significantly affects the cell performance because of an increase in shunt resistance associated with the formation of Na2SeX and phase separation. The passivation effect attributed to the Al2O3 NSs is well studied using the bias-EQE measurement and J–V characteristics under dark and illuminated conditions. With the optimization of the Al2O3 NSs, the remarkable enhancement in the cell performance occurs, exhibiting a power conversion efficiency increase from 2.83% to 5.33%, demonstrating a promising method for improving ultrathin Cu(In,Ga)Se2 devices, and providing significant opportunities for further applications.
关键词： nanostructure,CIGS solar cells,Al2O3 passivation layer,glancing angle deposition
更新于2025-09-19 17:13:59
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Simulation of graded bandgap on backwall superstrate CIGS solar cells with MoOx electron reflection layer
摘要： A model of backwall superstrate CuInxGa(1?x)Se2 (CIGS) solar cell with MoOx as an electron reflection layer has been investigated by Solar Cell Capacitance Simulator (SCAPS). The influence of the CIGS absorber with different thicknesses on the performance of the CIGS solar cells with a flat bandgap structure is carefully analyzed. When the CIGS thickness is 400 nm, the device with 10 nm MoOx layer has the highest efficiency of 8.24%. To further increase the efficiency, a graded bandgap structure, near the MoOx layer, has been established, and the efficiency can be improved from 8.24% to 15.01% when the maximum bandgap value and the length of the graded region are 1.6 eV and 240 nm, respectively. The causes of efficiency enhancement by this graded bandgap structure are then studied. With an additional graded bangap structure in SCR, close to the CdS layer, the efficiency is slightly improved from 15.01% to 15.15%. Finally, the simulation results show that the efficiency can be increased from 15.15% to 16.26% when the thickness of MoOx is reduced from 10 nm to 1 nm.
关键词： backwall superstrate,MoOx,bandgap grading,CIGS solar cells,SCAPS
更新于2025-09-19 17:13:59
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Dataset on the generation of red-kinked current-voltage curves in Cu(In,Ga)Se2 solar cells due to buffer/window interfacial defects
摘要： Red-kinked current-voltage characteristics in silver nanowire transparent electrode based Cu(In,Ga)Se2 solar cells have been reported [1e3]. The author has recently revealed that the buffer/window interfacial defects cause the generation of red-kinked current-voltage characteristics in the solar cells [1]. This article provides the dataset regarding the red-kink for Cu(In,Ga)Se2 solar cells as a function of the donor density in n-type window and CdS buffer/window interfacial defect density. The data were obtained by the simulation for Cu(In,Ga)Se2 solar cells using SCAPS-1D. The data include current density-voltage curves, ?ll factor, open-circuit voltage, short-circuit current density, and ef?ciency in the solar cells, and energy band bending in the Cu(In,Ga)Se2 layer.
关键词： Red kink,SCAPS-1D,Buffer/window interface,CIGS,Solar cells
更新于2025-09-12 10:27:22
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Averaged angle-resolved electroreflectance spectroscopy on Cu(In,Ga)Se <sub/>2</sub> solar cells: Determination of buffer bandgap energy and identification of secondary phase
摘要： Currently, the use of Zn(O,S) as buffer material for Cu(In,Ga)Se2 (CIGS) solar cells is intensely studied in order to further boost the performance of these devices. In this context, nondestructive analytical tools are needed that enable the determination of buffer bandgap energies in the complete device. To this end, we developed a spectroscopic approach based on electroreflectance (ER). From a set of measured angle-resolved ER (ARER) spectra, an averaged modulus spectrum is numerically calculated. This method suppresses the commonly observed detrimental line-shape distortions due to interference effects in the layered device structure and thus enables the determination of bandgap energies even for thin buffer layers. To verify the working principle of ARER, we first apply it to CIGS absorber and CdS buffer layers. Then, we utilize it to investigate CIGS solar cells with Zn(O,S) buffers. All ARER results are compared to the results of diffuse ER, a technique previously developed for the suppression of interference fringes. We demonstrate that ARER is the superior ER method for nondestructive bandgap determination of thin buffer layers in complete CIGS solar cells. Moreover, a Cu containing compound was determined as a secondary phase in the Zn(O,S) buffer by combined ARER studies, scanning transmission electron microscopy, and energy-dispersive X-ray spectroscopy.
关键词： CIGS solar cells,secondary phase,bandgap energy,Zn(O,S) buffer,electroreflectance
更新于2025-09-12 10:27:22