Control of an interfacial MoSe2 layer in Cu2ZnSnSe4 thin film solar cells: 8.9% power conversion efficiency with a TiN diffusion barrier
TL;DR: In this paper, the authors showed that the control of an interfacial MoSe2 layer thickness and the introduction of an adequate Se partial pressure (PSe) during annealing are essential to achieve high efficiency CZTSe solar cells.
Abstract: We have examined Cu2ZnSnSe4 (CZTSe) solar cells prepared by thermal co-evaporation on Mo-coated glass substrates followed by post-deposition annealing under Se ambient. We show that the control of an interfacial MoSe2 layer thickness and the introduction of an adequate Se partial pressure (PSe) during annealing are essential to achieve high efficiency CZTSe solar cells—a reverse correlation between device performance and MoSe2 thickness is observed, and insufficient PSe leads to the formation of defects within the bandgap as revealed by photoluminescence measurements. Using a TiN diffusion barrier, we demonstrate 8.9% efficiency CZTSe devices with a long lifetime of photo-generated carriers.
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IBM1
451 citations
TL;DR: It is concluded that alternative back contacts will be important for future improvements in CZTS(e) quality.
Abstract: Experimental proof is presented for a hitherto undetected solid-state reaction between the solar cell material Cu(2)ZnSn(S,Se)(4) (CZTS(e)) and the standard metallic back contact, molybdenum. Annealing experiments combined with Raman and transmission electron microscopy studies show that this aggressive reaction causes formation of MoS(2) and secondary phases at the CZTS|Mo interface during thermal processing. A reaction scheme is presented and discussed in the context of current state-of-the-art synthesis methods for CZTS(e). It is concluded that alternative back contacts will be important for future improvements in CZTS(e) quality.
357 citations
TL;DR: In this paper, the authors discuss the current status of kesterite-based solar cells by focusing on three key aspects of the device: (i) the interface between the Kesterite absorber and the Mo back contact, (ii) the kesteritic absorber bulk defects and grain boundaries, and (iii) the interfaces between the buffer layer.
Abstract: Kesterite-based solar cells are attracting considerable attention in recent years, owing to the reduced toxicity and greater abundance of their constituent elements. In this brief review, we discuss the current status of this important technology by focusing on three key aspects of the device: (i) the interface between the kesterite absorber and the Mo back contact, (ii) the kesterite absorber bulk defects and grain boundaries and (iii) the interface between the kesterite absorber and the buffer layer. By identifying key issues to be addressed, we provide suggestions for their potential improvement and future research. Copyright © 2016 John Wiley & Sons, Ltd.
317 citations
Cites background from "Control of an interfacial MoSe2 lay..."
...A TiN barrier layer deposited at the Mo/CZTS interface allows for a good grain structure at a high annealing temperature of 570 °C, while keeping MoSe2 thickness within acceptable limits (<300 nm) [44]....
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...A ~1300-nmthick MoSe2 layer was observed to increase the device resistance and degrade Voc [3,44]....
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TL;DR: A recent meeting of experts in kesterite, chalcopyrite, and related thin-film solar cell devices; characterization; and modeling from industry, academia, and national labs identified high-impact pathways forward in Kesterite photovoltaics research, towards the end-goal of achieving high-efficiency (>18%) devices in an accelerated timeframe as discussed by the authors.
Abstract: A recent meeting of experts in kesterite, chalcopyrite, and related thin-film solar cell devices; characterization; and modeling from industry, academia, and national labs identified high-impact pathways forward in kesterite photovoltaics research, towards the end-goal of achieving high-efficiency (>18%) devices in an accelerated timeframe. This paper summarizes the conclusions of this meeting while providing background on key areas of kesterite research. This paper does not aim to provide a comprehensive status-of-the-field review but rather to suggest specific and targeted areas where additional focus might yield the highest-impact results.
297 citations
26 Feb 2018
TL;DR: All aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials are provided in a comprehensive yet concise treatment.
Abstract: Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS2, MoSe2, MoTe2, WS2 and WSe2, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1–2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.
296 citations
References
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TL;DR: In this article, an upper theoretical limit for the efficiency of p−n junction solar energy converters, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of holeelectron pairs is radiative as required by the principle of detailed balance.
Abstract: In order to find an upper theoretical limit for the efficiency of p‐n junction solar energy converters, a limiting efficiency, called the detailed balance limit of efficiency, has been calculated for an ideal case in which the only recombination mechanism of hole‐electron pairs is radiative as required by the principle of detailed balance. The efficiency is also calculated for the case in which radiative recombination is only a fixed fraction fc of the total recombination, the rest being nonradiative. Efficiencies at the matched loads have been calculated with band gap and fc as parameters, the sun and cell being assumed to be blackbodies with temperatures of 6000°K and 300°K, respectively. The maximum efficiency is found to be 30% for an energy gap of 1.1 ev and fc = 1. Actual junctions do not obey the predicted current‐voltage relationship, and reasons for the difference and its relevance to efficiency are discussed.
11,071 citations
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
IBM1
TL;DR: In this article, a power conversion efficiency record of 10.1% was achieved for kesterite absorbers, using a Cu2ZnSn(Se,S)4 thin-film solar cell made by hydrazine-based solution processing.
Abstract: A power conversion efficiency record of 10.1% was achieved for kesterite absorbers, using a Cu2ZnSn(Se,S)4 thin-film solar cell made by hydrazine-based solution processing. Key device characteristics were compiled, including light/dark J–V, quantum efficiency, temperature dependence of Voc and series resistance, photoluminescence, and capacitance spectroscopy, providing important insight into how the devices compare with high-performance Cu(In,Ga)Se2. The record kesterite device was shown to be primarily limited by interface recombination, minority carrier lifetime, and series resistance. The new level of device performance points to the significant promise of the kesterites as an emerging and commercially interesting thin-film technology. Copyright © 2011 John Wiley & Sons, Ltd.
749 citations
TL;DR: In this paper, high efficiency solar cells with up to 6.8% efficiency were obtained with absorber layer thicknesses less than 1μm and annealing times in the minutes.
Abstract: High efficiency Cu2ZnSnS4 solar cells have been fabricated on glass substrates by thermal evaporation of Cu, Zn, Sn, and S. Solar cells with up to 6.8% efficiency were obtained with absorber layer thicknesses less than 1 μm and annealing times in the minutes. Detailed electrical analysis of the devices indicate that the performance of the devices is limited by high series resistance, a “double diode” behavior of the current voltage characteristics, and an open circuit voltage that is limited by a carrier recombination process with an activation energy below the band gap of the material.
588 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