Optimisation of rear reflectance in ultra-thin CIGS solar cells towards &gt;20% efficiency

Poncelet, Olivier; Kotipalli, Raja Venkata Ratan; Vermang, Bart; Macleod, Angus; Francis, Laurent; Flandre, Denis

doi:10.1016/j.solener.2017.03.001

Cited by 41 publications

(20 citation statements)

References 46 publications

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“…By increasing the light path in the absorber, this drawback can be avoided. These effects can be obtained by introducing excellent rear reflecting structures [32,34,43,45]. Therefore, a major part of the light that is not absorbed into the CIGS layer during the first passage is reflected back into the absorber during the second time (and possibly during the following times), increasing…”

Section: Importance Of Rear-reflection In Ultra-thin Cigs Solar Cellsmentioning

confidence: 99%

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Kotipalli

Poncelet

et al. 2017

Solar Energy

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We present a (1-D) SCAPS device model to address the following: (i) the surface passivation mechanisms (i.e. field-effect and chemical), (ii) their impact on the CIGS solar cell performance for varying CIGS absorber thickness, (iii) the importance of fixed charge type (+/-) and densities of fixed and interface trap charges, and (iv) the reasons for discrete gains in the experimental cell efficiencies (previously reported) for varying CIGS absorber thickness. First, to obtain a reliable device model, the proposed set of parameters is validated for both field-effect (due to fixed charges) and chemical passivation (due to interface traps) using a simple M-IS test structure and experimentally extracted values (previously reported) into the SCAPS simulator. Next, we provide figures of merits without any significant loss in the solar cell performances for minimum net-Qf and maximum acceptable limit for Dit, found to be ~5x10 12 cm-2 and ~1x10 13 cm-2 eV-1 respectively. We next show that the influence of negative fixed charges in the rear passivation layer (i.e. field-effect passivation) is more predominant than that of the positive fixed charges (i.e. counter-field effect) especially while considering ultra-thin (< 0.5 μm) absorber layers. Furthermore, we show the importance of rear reflectance on the short-circuit photocurrent densities while scaling down the CIGS absorber layers below 0.5 μm under interface chemical and field-effect passivation mechanisms. Finally, we provide the optimal rear passivation layer parameters for efficiencies greater than 20% with ultra-thin CIGS absorber thickness (< 0.5 μm). Based on these simulation results, we confirm that a negatively charged rear surface passivation with nano-point contact approach is efficient for the enhancement of cell performances, especially while scaling down the absorber thickness below 0.5 μm.

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Section: Importance Of Rear-reflection In Ultra-thin Cigs Solar Cellsmentioning

confidence: 99%

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Kotipalli

Poncelet

et al. 2017

Solar Energy

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“…Commonly, Mo films prepared by RF sputtering have better adhesion to the substrate and higher reflectance but lower conductivity than those prepared by DC sputtering under the same sputtering conditions, but the Mo films prepared by DC sputtering have better conductivity [16]. Actually, the reflectance of Mo back electrode is also very important to the Cu(In,Ga)Se 2 (CIGS), copper zinc tin sulphur (CZTS) and other solar cells, because higher reflectance can improve their photo-conversion efficiency [17].…”

Section: Introductionmentioning

confidence: 99%

Effects of Bottom Layer Sputtering Pressures and Annealing Temperatures on the Microstructures, Electrical and Optical Properties of Mo Bilayer Films Deposited by RF/DC Magnetron Sputtering

2019

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Most of the molybdenum (Mo) bilayer films are deposited by direct current (DC) magnetron sputtering at the bottom and the top layer (DC/DC). However, the deposition of Mo bilayer film by radio frequency (RF) Mo bottom layer and DC Mo top layer magnetron sputtering has been less studied by researchers. In this paper, the bottom layer of Mo bilayer film was deposited by RF magnetron sputtering to maintain its good adhesion and high reflectance, and the top layer was deposited by DC magnetron sputtering to obtain good conductivity (RF/DC). Generally, the bottom layer sputtering pressure is relatively random, in this paper, the effects of the bottom layer RF sputtering pressures on the microstructures and properties of Mo bilayer films were first studied in detail. Next, in order to further improve their properties, the as-prepared Mo bilayer films at 0.4 Pa bottom layer RF sputtering pressure were annealed at different temperatures and then investigated. Specifically, Mo bilayer films were deposited on soda-lime glass substrates by RF/DC magnetron sputtering at different bottom layer RF sputtering pressures in the range of 0.4-1.2 Pa, the powers of bottom layer RF sputtering and top layer DC sputtering were 120 W and 100 W, respectively. Then, Mo bilayer films, prepared at a bottom layer sputtering pressure of 0.4 Pa and top layer sputtering pressure of 0.3 Pa, were annealed for 30 min at various temperatures in the range of 100-400 • C. The effects of bottom layer sputtering pressures and the annealing temperatures on the microstructures, electrical and optical properties of Mo bilayer films were clarified by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic-force microscopy (AFM), and ultraviolet (UV)-visible spectra, respectively. It is shown that with decreasing bottom layer sputtering pressure from 1.2 to 0.4 Pa and increasing annealing temperature from 100 to 400 • C, the crystallinity, electrical and optical properties of Mo bilayer films were improved correspondingly. The optimized Mo bilayer film was prepared at the top layer sputtering pressure of 0.3 Pa, the bottom layer sputtering pressure of 0.4 Pa and the annealing temperature of 400 • C. The extremely low resistivity of 0.92 × 10 −5 Ω.cm was obtained. The photo-conversion efficiency of copper indium gallium selenium (CIGS) solar cell with the optimized Mo bilayer film as electrode was up to as high as 13.5%.

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“…From preliminary simulation (see Table S1), we estimate that the achievable current gain for a device with graded absorber is around 1 mAcm −2 with an Al/IZO layer combination. More extensive simulations for a variety of back contacts with increased reflectance were reported recently . Room temperature sputtered IZO was chosen because of the rather low NIR absorption as well as its amorphous/flat morphology.…”

Section: Introductionmentioning

confidence: 99%

Novel back contact reflector for high efficiency and double‐graded Cu(In,Ga)Se₂ thin‐film solar cells

Bissig

Carron

Greuter

et al. 2018

Progress in Photovoltaics

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For highest efficiency Cu(In,Ga)Se2 thin‐film solar cells, the V‐shaped bandgap grading can result in residual transmission through the absorber layer and parasitic absorbance in the Mo back contact. To improve the back contact reflectance, absorbers were grown in a multistage process on Mo/Al/InZnO substrates. Additionally, ultrathin layers of Mo and MoSeX were introduced at the InZnO‐absorber interface. Effects of the different back contacts on device performance, absorber morphology, and composition are characterized and discussed. Finally, a numerical model is proposed to understand the experimentally observed increase in device current density of 0.3 to 0.8 mAcm−2.

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Optimisation of rear reflectance in ultra-thin CIGS solar cells towards >20% efficiency

Abstract: This is the accepted version of a paper published in Solar Energy. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.

Cited by 41 publications

References 46 publications

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Effects of Bottom Layer Sputtering Pressures and Annealing Temperatures on the Microstructures, Electrical and Optical Properties of Mo Bilayer Films Deposited by RF/DC Magnetron Sputtering

Novel back contact reflector for high efficiency and double‐graded Cu(In,Ga)Se₂ thin‐film solar cells

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Optimisation of rear reflectance in ultra-thin CIGS solar cells towards >20% efficiency

Abstract: This is the accepted version of a paper published in Solar Energy. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.

Cited by 41 publications

References 46 publications

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Addressing the impact of rear surface passivation mechanisms on ultra-thin Cu(In,Ga)Se2 solar cell performances using SCAPS 1-D model

Effects of Bottom Layer Sputtering Pressures and Annealing Temperatures on the Microstructures, Electrical and Optical Properties of Mo Bilayer Films Deposited by RF/DC Magnetron Sputtering

Novel back contact reflector for high efficiency and double‐graded Cu(In,Ga)Se2 thin‐film solar cells

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Product

Resources

About

Novel back contact reflector for high efficiency and double‐graded Cu(In,Ga)Se₂ thin‐film solar cells