Thin film solar cell with 8.4% power conversion efficiency using an earth‐abundant Cu2ZnSnS4 absorber
IBM1
TL;DR: In this paper, a vacuum process was used to construct a pure sulfide Cu2ZnSnS4 solar cell with 8.4% efficiency, a number independently certified by an external, accredited laboratory.
Abstract: Using vacuum process, we fabricated Cu2ZnSnS4 solar cells with 8.4% efficiency, a number independently certified by an external, accredited laboratory. This is the highest efficiency reported for pure sulfide Cu2ZnSnS4 prepared by any method. Consistent with literature, the optimal composition is Cu-poor and Zn-rich despite the precipitation of secondary phases (e.g., ZnS). Despite a very thin absorber thickness (~600 nm), a reasonably good short-circuit current was obtained. Time-resolved photoluminescence measurements suggest a minority carrier-diffusion length on the order of several hundreds of nanometers and relatively good collection of photo-carriers across the entire absorber thickness. Copyright © 2011 John Wiley & Sons, Ltd.
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789 citations
Cites methods from "Thin film solar cell with 8.4% powe..."
...Watson Research Center [16] using thermal evaporation and measured at the Newport Technology and Application Center’s Photovoltaic Lab....
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TL;DR: Yan et al. as mentioned in this paper used heat treatment to reduce non-radiative recombination within the heterojunction region, which is a major cause of limiting voltage output and overall performance.
Abstract: Sulfide kesterite Cu2ZnSnS4 provides an attractive low-cost, environmentally benign and stable photovoltaic material, yet the record power conversion efficiency for such solar cells has been stagnant at around 9% for years. Severe non-radiative recombination within the heterojunction region is a major cause limiting voltage output and overall performance. Here we report a certified 11% efficiency Cu2ZnSnS4 solar cell with a high 730 mV open-circuit voltage using heat treatment to reduce heterojunction recombination. This heat treatment facilitates elemental inter-diffusion, directly inducing Cd atoms to occupy Zn or Cu lattice sites, and promotes Na accumulation accompanied by local Cu deficiency within the heterojunction region. Consequently, new phases are formed near the hetero-interface and more favourable conduction band alignment is obtained, contributing to reduced non-radiative recombination. Using this approach, we also demonstrate a certified centimetre-scale (1.11 cm2) 10% efficiency Cu2ZnSnS4 photovoltaic device; the first kesterite cell (including selenium-containing) of standard centimetre-size to exceed 10%. The emerging kesterite Cu2ZnSnS4 solar cell offers a potential low-cost, non-toxic, materially abundant platform for next-generation photovoltaics, yet its efficiency has been mired below 10%. Yan et al. now use post-heat treatment of the heterojunction to show device efficiencies that surpass 10%.
586 citations
TL;DR: In this paper, the use of vacuum co-evaporation to produce Cu2ZnSnSe4 photovoltaic devices with 9.15% total area efficiency is described.
586 citations
TL;DR: In this paper, the authors present a list of the highest independently confirmed efficiencies for solar cells and modules and provide guidelines for inclusion of results into these tables and new entries since January 2010 are reviewed.
Abstract: Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since January 2010 are reviewed. Copyright # 2010 John Wiley & Sons, Ltd.
557 citations
Cites methods from "Thin film solar cell with 8.4% powe..."
...Watson Research Center [16] using thermal evaporation and measured at the Newport Technology and Application Center’s Photovoltaic Lab....
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IBM1
451 citations
References
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Book•
01 Jan 1967
TL;DR: The Planar Technology of Semiconductor Surfaces is described in this article, where it is shown that the planar planar technology can be used to model the surface effects on p-n junction transistors.
Abstract: The Planar Technology. Solid-State Technology. Vapor-Phase Growth. Thermal Oxidation. Solid-State Diffusion. Semiconductors and Semiconductor Devices. Elements of Semiconductor Physics. Semiconductors under Non-Equilibrium Conditions. p-n Junction. Junction Transistor. Junction Field-Effect Transistors. Surface Effects and Surface-Controlled Devices. Theory of Semiconductor Surfaces. Surface Effects on p-n Junctions. Surface Field-Effect Transistors. Properties of the Silicon-Silicon Dioxide System.
2,394 citations
IBM1
TL;DR: In this article, the development of kesterite-based Cu 2 ZnSn(S,Se) 4 (CZTSSe) thin-film solar cells, in which the indium and gallium from CIGSSe are replaced by the readily available elements zinc and tin, is reviewed.
1,151 citations
IBM1
TL;DR: A non-vacuum, slurry-based coating method that combines advantages of both solution processing and particlebased deposition is shown, enabling fabrication of Cu2ZnSn(Se,S)4 devices with over 9.6% efficiency—a factor of five performance improvement relative to previous attempts to use highthroughput ink-based approaches and >40% higher than previous record devices prepared using vacuum-based methods.
Abstract: 2010 WILEY-VCH Verlag Gmb Chalcogenide-based solar cells provide a critical pathway to cost parity between photovoltaic (PV) and conventional energy sources. Currently, only Cu(In,Ga)(S,Se)2 (CIGS) and CdTe technologies have reached commercial module production with stable power conversion efficiencies of over 9 percent. Despite the promise of these technologies, restrictions on heavy metal usage for Cd and limitations in supply for In and Te are projected to restrict the production capacity of the existing chalcogen-based technologies to <100GWp per year, a small fraction of our growing energy needs, which are expected to double to 27 TW by 2050. Earth-abundant copper-zinc-tin-chalcogenide kesterites, Cu2ZnSnS4 and Cu2ZnSnSe4, have been examined as potential alternatives for the two leading technologies, reaching promising but not yet marketable efficiencies of 6.7% and 3.2%, respectively, by multilayer vacuum deposition. Here we show a non-vacuum, slurry-based coating method that combines advantages of both solution processing and particlebased deposition, enabling fabrication of Cu2ZnSn(Se,S)4 devices with over 9.6% efficiency—a factor of five performance improvement relative to previous attempts to use highthroughput ink-based approaches and >40% higher than previous record devices prepared using vacuum-based methods. To address the issue of cost, non-vacuum ‘‘ink’’-based approaches—both from solutions and suspensions—are being developed for chalcogenide-based absorber layer deposition to replace potentially more expensive vacuum-based techniques. True solutions allow intermixing of the constituents at a molecular level and the formation of smooth homogeneous films, as demonstrated with spin-coated CIGS absorber layers from hydrazine (N2H4) solutions. [11–13] The chemically reducing character of hydrazine stabilizes solutions of anions with direct metal-chalcogen bonding for select elements (e.g. Cu, In, Ga, Sn), without the necessity to introduce typical impurities (e.g., C, O, Cl). Suspension approaches employ solid particles designed to be deposited on a substrate and reacted or fused with each other, to form a desired crystalline phase and grain structure. Normally insoluble components can be deposited by this approach using typical liquid-based deposition (e.g., printing, spin coating, slit casting, spraying). Although high-quality large-grained absorber layers can be formed for selected systems using either solutionor particlebased deposition, numerous challenges confront each approach for more general deposition needs. Solution processing is limited by the solubility of many materials of interest (e.g., ZnSe1–xSx in hydrazine solvents—relevant for the deposition of Cu2ZnSnS4 or Cu2ZnSnSe4). In addition, volume contraction upon drying of solution-deposited layers creates stress in the film that may cause crack formation in thicker films. In suspension approaches, a common difficulty is achieving single-phase crystallization among the solid particles. Particle-based approaches (as well as some solution methods) typically require the addition of organic agents to improve wetting and particle dispersion, and to avoid film cracks and delamination. Most of these non-volatile organic additives introduce carbon contamination in the final layer. Because of these challenges, vacuum-based techniques have historically shown superior performance to liquid coating. In the case of the earth-abundant Cu2ZnSn(S,Se)4 materials, ink-based approaches have to date yielded at most <1.6% efficiency devices. Here we demonstrate an hybrid solution-particle approach, using the earth-abundant Cu2ZnSn(S,Se)4 system as an example, which enables fabrication of PV devices with over 9.6% power conversion efficiency. The slurry (or ink) employed for deposition comprises a Cu–Sn chalcogenide (S or S–Se) solution in hydrazine (see Experimental section), with the in situ formation of readily dispersible particle-based Zn-chalcogenide precursors, ZnSe(N2H4) (Figure 1a,d) or ZnS(N2H4) (Figure 1b). Thermogravimetric analysis (TGA) of the isolated selenide particle precursor shows decomposition at approximately 200 8C, with mass loss of about 20%, close to the theoretical value expected upon transition to pure ZnSe (Figure 1c,d). Deposition using this hybrid slurry successfully combines the advantages of solution and suspension deposition routes by use of solutions containing solid particles, wherein both components (i.e., solution and particle) contain metal and chalcogen elements that integrate into the final film. Using the hybrid slurry method (i) solubility limitations are resolved, as virtually any materials system can be constituted by a combination of solid and dissolved components; (ii) the dissolved components can be engineered as an efficient binding media for the particles, eliminating the need of separate organic binders; (iii) solid particles act as stress-relief and crack-deflection centers allowing the deposition of thicker layers than pure solution processes; and (iv) the intimate contact between the two phases allows rapid reaction and homogeneous phase formation. Complete conversion of all constituents of the spin-coated hybrid precursor films into a single-phase, highly crystalline Cu2ZnSn(S,Se)4 is achieved by annealing at 540 8C on a hot plate. Three main types of samples were targeted – high selenium content (A), intermediate sulfoselenide (B) and pure sulfide (C) –
1,085 citations
"Thin film solar cell with 8.4% powe..." refers background or methods in this paper
...[11] demonstrated the power conversion efficiency of 9....
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...Various approaches have been reported to fabricate Cu2ZnSnS4 (CZTS) layers including thermal co-evaporation [3–5], sputtering [6,7], pulsed laser deposition [8], electroplating [9,10], and solution process [11,12]....
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TL;DR: A roadmap emphasizing low-cost alternatives that could become a dominant new approach for photovoltaics research and deployment is developed and it is found that devices performing below 10% power conversion efficiencies deliver the same lifetime energy output as those above 20% when a 3/4 material reduction is achieved.
Abstract: Solar photovoltaics have great promise for a low-carbon future but remain expensive relative to other technologies Greatly increased penetration of photovoltaics into global energy markets requires an expansion in attention from designs of high-performance to those that can deliver significantly lower cost per kilowatt-hour To evaluate a new set of technical and economic performance targets, we examine material extraction costs and supply constraints for 23 promising semiconducting materials Twelve composite materials systems were found to have the capacity to meet or exceed the annual worldwide electricity consumption of 17 000 TWh, of which nine have the potential for a significant cost reduction over crystalline silicon We identify a large material extraction cost (cents/watt) gap between leading thin film materials and a number of unconventional solar cell candidates including FeS2, CuO, and Zn3P2 We find that devices performing below 10% power conversion efficiencies deliver the same lifetime en
1,071 citations
"Thin film solar cell with 8.4% powe..." refers background in this paper
...The details of annual electricity production potential for different photovoltaic materials are provided in [2]....
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TL;DR: By tuning the composition of the CZTS nanocrystals and developing a robust film coating method, a total area efficiency as high as 7.2% under AM 1.5 illumination and light soaking has been achieved.
Abstract: Earth abundant copper-zinc-tin-chalcogenide (CZTSSe) is an important class of material for the development of low cost and sustainable thin film solar cells. The fabrication of CZTSSe solar cells by selenization of CZTS nanocrystals is presented. By tuning the composition of the CZTS nanocrystals and developing a robust film coating method, a total area efficiency as high as 7.2% under AM 1.5 illumination and light soaking has been achieved.
915 citations
"Thin film solar cell with 8.4% powe..." refers methods in this paper
...Various approaches have been reported to fabricate Cu2ZnSnS4 (CZTS) layers including thermal co-evaporation [3–5], sputtering [6,7], pulsed laser deposition [8], electroplating [9,10], and solution process [11,12]....
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