We present a method for high-rate solution growth of the Zn(O,S) buffer layer to achieve deposition rates and material consumptions far below the standard Zn(O,S) and CdS deposition method. We ...replace the organosulfide thiourea by the more quickly decomposable thioacetamide and control the reaction kinetics by the use of chelating ligands and ammonia. We characterize the produced layers by secondary neutral mass spectrometry, X-ray diffraction, and optical transmission. For cell preparation, we use high-efficiency Cu(In,Ga)Se 2 with an alkali-modified surface, as well as industrially relevant inline absorber material. We realize a certified 21% cell efficiency with the standard thiourea-based Zn(O,S) and first cells with over 19 % with the high-rate Zn(O,S) buffer.
This work investigates the impact of opto-electronical buffer (b) and high resistive window layer (w) properties, i.e. band gap Eg(b,w) and electron affinity χe(b,w), on the device performance of ...chalcopyrite CuIn1−xGaxSe2 (CIGS) solar cells by numerical simulations with SCAPS. We established an initial device model based on an experimental device and its J–V, C–V, and EQE data at room temperature as well as its quantified depth profile for the Ga/(Ga+In) ratio (GGI). The device features a non-uniform CIGS doping profile as well as a strongly doped CIGS surface layer. Based on our simulations that include various buffer layer materials, we argue that the most suitable buffer and window layer is Zn1−zMgzO. The potential gain in efficiency is up to 0.9% absolute which corresponds to a relative gain of 4.1%.
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•Numerical simulations of buffer/window layers based on an experimental CIGS device.•Device model features: OVC-layer, non-uniform CIGS doping, interface defect.•Sensitivity analysis on CIGS conduction band edge position χe(CIGS).•Best: negligible conduction band offset Δχe between CIGS and buffer layer.•Most suitable buffer and window layer is ZMO(y), y critically depends on χe(CIGS).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Abstract
The efficiency of Cu(In,Ga)Se
2
(CIGS)-based solar cells could be continuously increased up to 22.6% by employing alkali metal dopants like Na, K, Rb, and Cs. The alkali metals are supplied ...to the CIGS layer from the glass substrate during deposition, from precursor layers or by a post deposition treatment. The alkali metal distribution in CIGS is not homogenous. Independently of the alkali metals used, their concentration at grain boundaries is much higher than that inside the grains. In this contribution, we discuss thermodynamic limitations for alkali metals in CIGS and show that in higher concentrations they are responsible for secondary phase separation. Applying the concept of immiscibility of phases for alkali metals in CIGS, we suggest how segregation at grain boundaries, formation of clusters in CIGS grains, sporadic formation of microstructures in the CIGS layer (hotspots, nodules), and separation of secondary phases with ordered structures can be interpreted.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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The Centre for Solar Energy and Hydrogen Research Baden‐Württemberg (ZSW) has nudged up the performance bar for thin‐film solar cells yet another notch. The ...Stuttgart‐based scientists have achieved 22.6 percent efficiency with a Cu(In,Ga)Se2 (CIGS) solar cell. One of the major strategies used to achieve this milestone was the application of a post‐deposition treatment (PDT) on the CIGS absorber material with alkali elements. Initially this treatment was used by researchers to supply sodium to flexible CIGS devices in order to thereby boost the open circuit voltage. However, exchanging potassium for sodium brought yet another performance boost in the past three years. The Letter on pp. 583–586 describes the impact even heavier alkali elements like rubidium and cesium have on CIGS device performance when applied with the same PDT procedure: another performance gain can be demonstrated. In addition, the observed effect on the device level is investigated on the atomic scale by secondary ion mass spectrometry (SIMS). A competitive interaction between light and heavy alkali elements is detected. With these results and analytical findings, CIGS once more proves to be a scientifically interesting and economically promising second generation PV technology for the near future.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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