In this paper, we investigated the effect of rapid thermal annealing (RTA) on solar cell performance. An opto-electric conversion efficiency of 11.75% (Voc=0.64 V, Jsc = 25.88mA/cm2 , FF=72.08%) was obtained under AM 1.5G when the cell was annealed at 300℃ for 30s. The annealed solar cell showed an average absolute efficiency 1.5% higher than that of the as-deposited one. For the microstructure analysis and the physical phase confirmation, X-ray diffraction (XRD), Raman spectra, front surface reflection (FSR), internal quantum efficiency (IQE), and X-ray photoelectron spectroscopy (XPS) were respectively applied to distinguish the causes inducing the efficiency variation. All experimental results implied that the RTA eliminated recombination centers at the p-n junction, reduced the surface optical losses, enhanced the blue response of the CdS buffer layer, and improved the ohmic contact between Mo and Cu(In, Ga)Se2 (CIGS) layers. This leaded to the improved performance of CIGS solar cell. 相似文献
In this study, Cu(In,Ga)(Se,S)2 (CIGSS) thin films were deposited onto a bi-layer Mo coated soda-lime glass by co-sputtering a chalcopyrite Cu(In,Ga)Se2 (CIGS) quaternary alloy target and an In2S3 binary target. A one-stage annealing process was performed to form CIGSS chalcopyrite phase without post-selenization. Experimental results show that CIGSS films were prepared by the proposed co-sputter process via CIGS (70 W by radio frequency) and In2S3 (30 W by direct current) with a substrate temperature of 373 K, working pressure of 0.67 Pa, and one-stage annealing at 798 K for 30 min. The stoichiometry ratios of the CIGSS film were Cu/(In + Ga) = 0.92, Ga/(In + Ga) = 0.26, and Se/(S) = 0.49 that approached device-quality stoichiometry ratio (Cu/(In + Ga) < 0.95, Ga/(In + Ga) < 0.3, and (Se/S) ≈ 0.5). The resistivity of the sample was 14.8 Ω cm, with a carrier concentration of 3.4 × 1017 cm−3 and mobility of 1.2 cm2 V−1 s−1. The resulting film exhibited p-type conductivity with a double graded band-gap structure. 相似文献
In this article, the performances of Cu(In,Ga)Se2 (CIGS) solar cells have been modelled and numerically simulated using the one-dimensional simulation program Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D), and a detailed analysis of the effect of surface defect layer (SDL) thickness, band gap and carrier mobility with Fermi level pinning is presented. Furthermore, donor-type defect state density in the SDL has been investigated, and their effect on device performances has been presented. Based on the simulation results, optimal properties of the SDL for the CIGS solar cell are proposed. The simulated results show that the optimal thickness of the SDL to optimise the solar cells is in the range of 100–200 nm. The increase in the band gap of the SDL >1.3 eV improves the device performance by enhancing the open-circuit voltage (Voc), fill factor (FF) and conversion efficiency due to the larger quasi-Fermi energy-level splitting, and optimal band offset between the SDL and the buffer layer (CdS). The simulation results suggest that the SDL defect density as well as carrier mobilities are the critical parameters for the limitation of the performances for the CIGS solar cells. All these results show that the SDL plays an important role in designing high-efficiency and high-performance CIGS-based solar cells. 相似文献
Thin films of Cu(In, Ga)Se2 (CIGS) with a Ga/(Ga + In) ratio of ~0.27 corresponding to the standard elemental composition for solar-energy transducers
were grown on Mo-coated glass substrates by the Cu, In, Ga, and Se co-evaporation technique from different sources. Transmission
(T), photoluminescence (PL), and photoluminescence excitation (PLE) spectra at 4.2 K were used to analyze electronic properties
in the asgrown and electron-irradiated CIGS films. The band-gap energy (Eg) of the CIGS films measured using both transmission and PLE methods was found to be about 1.28 eV at 4.2 K. Two deep bands
in the PL spectra of the irradiated CIGS films, P1 at ~0.91 eV and P2 at ~0.77 eV, have been detected. These bands are tentatively associated with copper atoms substituting indium (CuIn) and indium vacancies VIn, respectively, as the simplest radiation-induced defects. 相似文献
Alkali‐free Cu(In,Ga)Se2(CIGS) absorbers grown on Mo‐coated alumina (Al2O3) substrates were doped with potassium (K) after CIGS growth by a potassium fluoride (KF) post‐deposition treatment (PDT). The addition of K to the absorber leads to a strong increase in cell efficiency from 10.0% for the K‐free cell to 14.2% for the K‐doped cell, mainly driven by an increase in the open‐circuit voltage Voc and the fill factor FF, and to an increase in the net charge carrier density. Hence K doping by KF‐PDT is comparable to doping with Na.
This study examined the effects of Ga content in the CIGS absorber layer on the properties of the corresponding thin films and solar cells fabricated using a co-evaporation technique. The grain size of CIGS films decreased with increasing Ga content presumably because Ga diffusion during the 2nd stage of the co-evaporation process is more difficult than In diffusion. The main XRD peaks showed a noticeable shift to higher diffraction angles with increasing Ga content, which was attributed to Ga atoms substituting for In atoms in the chalcopyrite structure. Band gap energy and the net carrier concentration of CIGS films increased with Ga/(In + Ga) ratios. Regarding the solar cell parameters, the short circuit current density (JSC) decreased linearly with Ga/(In + Ga) ratios due to the lack of absorption in the long-wavelength portion of the spectrum, while the open circuit voltage (VOC) increase with those. However, VOC values at high Ga/(In + Ga) regions (>0.35) was far below than those extrapolated from the low Ga contents regions, finally resulting in an optimum Ga/(In + Ga) ratio of 0.28 where the solar cell showed the highest efficiency of 15.56% with VOC, JSC and FF of 0.625 V, 35.03 mA cm−2 and 0.71, respectively. 相似文献
The chalcopyrite semiconductor, Cu(InGa)Se2 (CIGS), is popular as an absorber material for incorporation in high-efficiency photovoltaic devices because it has an appropriate band gap and a high absorption coefficient. To improve the efficiency of solar cells, many research groups have studied the quantitative characterization of the CIGS absorber layers. In this study, a compositional analysis of a CIGS thin film was performed by depth profiling in secondary ion mass spectrometry (SIMS) with MCs+ (where M denotes an element from the CIGS sample) cluster ion detection, and the relative sensitivity factor of the cluster ion was calculated. The emission of MCs+ ions from CIGS absorber elements, such as Cu, In, Ga, and Se, under Cs+ ion bombardment was investigated using time-of-flight SIMS (TOF-SIMS) and magnetic sector SIMS. The detection of MCs+ ions suppressed the matrix effects of varying concentrations of constituent elements of the CIGS thin films. The atomic concentrations of the CIGS absorber layers from the MCs+-SIMS exhibited more accurate quantification compared to those of elemental SIMS and agreed with those of inductively coupled plasma atomic emission spectrometry. Both TOF-SIMS and magnetic sector SIMS depth profiles showed a similar MCs+ distribution for the CIGS thin films. 相似文献
Cu(In,Ga)Se2 (CIGSe) thin film solar cells were fabricated by direct inkjet printing of Cu(In,Ga)S2 (CIGS) nanoparticles followed by rapid thermal annealing under selenium vapor. Inkjet printing is a low-cost, low-waste, and flexible patterning method which can be used for deposition of solution-based or nanoparticle-based CIGS films with high throughput. XRD and Raman spectra indicate that no secondary phase is formed in the as-deposited CIGS film since quaternary chalcopyrite nanoparticles are used as the base solution for printing. Besides, CIGSe films with various Cu/(In + Ga) ratios could be obtained by finely tuning the composition of CIGS nanoparticles contained in the ink, which was found to strongly influence the devices performance and film morphology. To date, this is the first successful fabrication of a solar device by inkjet printing of CIGS nanoparticles. 相似文献
Using a reactive co-sputtering from Cu0.6Ga0.4 and Cu0.4In0.6 alloy targets, we prepared CuIn1−xGaxSe2 (CIGS) thin films on Mo/soda-lime glass (SLG) in association with a thermal cracker for elemental atomic Se radicals. The film growth was performed at 500 °C for 90 min. To achieve the composition ratio of CIGS absorber layer, Cu0.6Ga0.4 target was set at RF power of 50 W, 60 W, 70 W, and 80 W while keeping at 100 W for Cu0.4In0.6 alloy target. Post-annealing was done for all the CIGS films at 550 °C for 30 min. The composition ratio of [Cu]/[In + Ga] and [Ga]/[In + Ga] was increased with RF power but showed no change after post-annealing. X-ray diffraction analysis revealed all the samples has grown dominantly in the [112] crystal orientation. We found the Cu2−xSe and (InGa)2−xSe3 defect phase both at the surface and in the bulk, and developed with post-annealing. From the devices fabricated in the structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/soda-lime glass (SLG), the external quantum efficiency (EQE) was observed to improve in the wavelength, λ ≥ 550 nm in the samples treated with annealing. In the current–voltage (J–V) measurements, the solar cell showed the best performance of FF = 54.1%, Voc = 0.48 V, Jsc = 33.1 mA/cm2 and η = 8.5% in the sample with [Cu]/[In + Ga] = 0.84 that improved largely from η = 4.6% for the solar cell with an as-grown CIGS films. 相似文献
The present work is an attempt to prepare well defined surfaces of Cu(In,Ga)Se2 (CIGS) thin films in order to answer to basic questions about the relationship between bulk and surface composition. The approach is to use an oxidative etch with an aqueous bromine solution, known to lead to specular surfaces. The CIGS surface is then analyzed by mechanical profilometry, SEM and XPS, allowing for determination of the surface roughness and the nature of surface species. After short time bromine etch, a Se0 film is formed on the CIGS surface which can be completely removed by KCN treatment, leaving a CIGS specular surface. An highlight result is that under specific conditions, the surface composition is close to the stoichiometry of the Cu(In,Ga)3Se5 copper deficient phase. This is the first time that such a study is conducted on technology relevant thin polycrystalline CIGS film. It is expected that the method described will help conducting experiments (e.g. Angle resolved XPS, SIMS, etc.) with an improved resolution. 相似文献