Graded band-gap engineering for increased efficiency in CZTS solar cells

Ferhati, H.; Djeffal, F.

doi:10.1016/j.optmat.2018.01.006

Cited by 62 publications

(16 citation statements)

References 24 publications

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“…For this purpose, a major research and development focus has been devoted to design thinfilm solar cells with absorber thicknesses in the range 1-2 μm in order to reduce the elaboration cost of the PV module, while maintaining a high conversion efficiency approaching the Shockley-Queisser limit [5][6][7][8]. In this perspective, various strategies based on nanostructures, heterojunction, multilayers, tandem configuration, electrode engineering and band-gap grading have been proposed to improve the efficiency of thin-film solar cells [10][11][12][13][14][15][16]. Although the fact that these aspects have enabled exciting opportunities for reaching higher efficiencies, the scarcity of some elements, the processing complexity and the use of toxic materials constitute the main bottlenecks for their eventual deployment for building efficient PV panels.…”

Section: Introductionmentioning

confidence: 99%

Absorption enhancement in amorphous Si by introducing RF sputtered Ti intermediate layers for photovoltaic applications

Ferhati

Djeffal

Boubiche

et al. 2021

Materials Science and Engineering: B

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In this paper, embedded Amorphous-Silicon (a-Si) and Titanium (Ti) ultrathin-films forming a multilayer structure is proposed as a new efficient absorber material for thin-film solar cells (TFSCs). Promising design strategy based on combining FDTD (Finite Difference Time Domain) with Particle Swarm Optimization (PSO) was adopted to identify the a-Si/Ti multilayer geometry offering the highest Total Absorbance Efficiency (TAE). It is found that the optimized design can serve as an effective absorber, yielding superb TAE exceeding 80%.The optimized a-Si/Ti multilayer was then elaborated by successive growth of a-Si and Ti ultrathin layers using RF magnetron sputtering technique. The sputtered a-Si/Ti thin-film was characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and UV-Visible absorption spectroscopy. Measurements showed a unique optical behavior, promoting broadband absorbance over the visible and even NIR spectrum ranges. In particular, the prepared a-Si/Ti absorber exhibits an optical band-gap of 1.36 eV, which is suitable for photovoltaic applications. A performance assessment of the elaborated absorber was investigated by extracting I-V characteristics and electrical parameters under dark and 1-sun illumination. It is revealed that the proposed absorber demonstrates outstanding electrical and sensing performances. Therefore, promoting enhanced resistive behavior and light-scattering effects, this innovative concept of optimized a-Si/Ti multilayer provides a sound pathway for designing promising alternative absorbers for the future development of a-Si-based TFSCs.

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Section: Introductionmentioning

confidence: 99%

Absorption enhancement in amorphous Si by introducing RF sputtered Ti intermediate layers for photovoltaic applications

Ferhati

Djeffal

Boubiche

et al. 2021

Materials Science and Engineering: B

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“…К настоящему времени твердые растворы соединений A 3 B 5 получили широкое распространение в технологии ФЭП и применяются для p−n-переходов, а также в качестве широкозонных оптических окон, потенциальных барьеров и буферов для согласования периодов кристаллических решеток в многослойных гетероструктурах [1][2][3][4]. Физическая природа твердых растворов позволяет создавать изопериодные гетероструктуры [5][6][7], в которых рассогласование периодов кристаллических решеток слоя и подложки a = 0, и варизонные гетероструктуры [8][9][10], в которых ширина запрещенной зоны слоя изменяется по его толщине. Важным моментом при получении варизонных структур является создание на первой стадии роста изопериодного переходного слоя на гетерогранице для уменьшения ее дефектности, обусловленной термическими и упругими напряжениями несоответствия.…”

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“…Твердые растворы Al x In y Ga 1−x −y P z As 1−z на подложках GaAs представляют практический интерес, так как на их основе возможно получить слои, чувствительные в спектральном диапазоне 0.5−0.9 µm. Использование варизонных слоев позволяет за счет тянущего электрического поля, которое увеличивает поток носителей заряда к p−n-переходу, увеличить внешний квантовый выход ФЭП [9]. Преимущество пятикомпонентных твердых растворов соединений A 3 B 5 заключается в независимом (друг от друга) изменении ширины запрещенной зоны (E g ), периода кристаллической решетки (a) и коэффициента термического расширения.…”

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Варизонные гетероструктуры Al-=SUB=-x-=/SUB=-In-=SUB=-y-=/SUB=-Ga-=SUB=-1-x-y-=/SUB=-P-=SUB=-z-=/SUB=-As-=SUB=-1-z-=/SUB=-/GaAs для фотоэлектрических преобразователей

Lunin¹,

Lunina²,

Alfimova³

et al. 2021

Письма В Журнал Технической Физики

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The AlxInyGa1-x-yPzAs1-z/GaAs graded-gap heterostructures were grown by the temperature gradient zone recrystallization with a liquid zone reciprocating, where energy band gap varied from 1.43 to 2.2 eV. The influence of technological parameters on the varying in the energy band gap of the grown AlxInyGa1-x-yPzAs1-z/GaAs solid solutions is investigated. In the p-AlxInyGa1-x-yPzAs1-z/n-GaAs heterostructure, the maximum energy band gap gradient of 10490 eV/cm is reached, and an increase in the external quantum efficiency is shown in the wavelength range of 500-900 nm.

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“…In common with CIGS, CZTS is a direct band gap p-type semiconductor [81,82]. It also has a relatively high optical absorption coefficient of approximately 10 4 cm -1 for visible light [83]. It is possible to incorporate selenium into the lattice structure in partial substitution for sulphur, to create Cu2ZnSnSxSe4-x (CZTSSe), or to manufacture copper zinc tin selenide (Cu2ZnSnSe4 -CZTSe) [84].…”

Section: The Potential Of Copper Zinc Tin Sulphidementioning

confidence: 99%

“…It has already been established that CZTS possesses favourable properties with regard to having a suitable direct band gap of up to ~1.5 eV [84] and an optical absorption coefficient of ~10 4 cm -1 for visible light [83] (see section 1.1.3). This section will focus more on the physical properties of the material and how these translate to the performance of the absorber layer and solar cell.…”

Section: Materials Properties and Deposition Of Cztsmentioning

confidence: 99%

Fabrication of CZTS Solar Cells Using Electrodeposition Techniques

Riches¹

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Copper zinc tin sulphide (CZTS) is a p-type semiconductor that can be used as the light absorbing layer in thin-film heterojunction solar cells, with the specific advantage of being comprised only of non-toxic, earth abundant elements. There are many methods through which CZTS can by synthesised, one of which is electrodeposition, which is an industrially scalable process used extensively in the steel industry. This thesis details a study of the electrodeposition of stacked elemental layers and their subsequent sulphurisation in the manufacture of CZTS. A range of electrodeposition parameters are tested for each elemental layer, each of which is characterised through a range of techniques, including scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), which enables the development of optimised conditions. It was found that the deposition of copper favoured potentiostatic deposition, with a smooth granular structure being deposited onto molybdenum at -0.98V vs Hg|HgO from a sodium hydroxide based electrolyte, while tin required galvanostatic deposition from a methanesulfonic acid electrolyte in order to return consistent results. This was optimised to an initial high current density period of -20 mA cm-2 for 1.2 s to nucleate grains, falling to -5 mA cm-2 to minimise hydrogen evolution thereafter. Trial of numerous electrolyte formulae found that an acid-sulphate electrolyte gave the most promising results, with galvanostatic deposition at -50 mA cm-2 being found to be suitable. Optimised stacked elemental layer precursors are then progressed to the annealing and sulphurisation stage for conversion into CZTS. One key area of study is the inclusion of a pre-alloying annealing step prior to sulphurisation, and its effect on the morphology of the CZTS films and subsequent solar cell device performance. Pre-alloyed metallic films are extensively characterised by means of X-ray photoelectron spectroscopy (XPS) depth profiling, X-ray diffractometry (XRD) and EDS elemental mapping as part of an optimisation process, and Raman spectroscopy is used in conjunction with XRD and EDS in the analysis of CZTS films sulphurised in a rapid thermal processing (RTP) furnace. A pre-alloying step at 300 °C for 10 minutes was found to be sufficient for the deposited elements to fully intermix. It was discovered that not only does the inclusion of an optimised pre-alloying step improve the morphology of the CZTS films and the subsequent solar cell performance, but the integration of a pre-alloying stage with the sulphurisation in a single furnace operation does not lead to any evidence of disadvantage when compared with pre-alloying and sulphurisation processes conducted separately. In fact, 8 out of 45 cells with an integrated pre-alloying process achieved 0.1% efficiency or greater, compared to 5 out of 45 for those that underwent a separate pre-alloying process, and 0 out of 45 for those that received no pre-alloying process. This positive result for the integration of the pre-alloy offers simplification of the manufacturing process for a potential future scaled-up CZTS solar cell device.

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Graded band-gap engineering for increased efficiency in CZTS solar cells

Cited by 62 publications

References 24 publications

Absorption enhancement in amorphous Si by introducing RF sputtered Ti intermediate layers for photovoltaic applications

Absorption enhancement in amorphous Si by introducing RF sputtered Ti intermediate layers for photovoltaic applications

Варизонные гетероструктуры Al-=SUB=-x-=/SUB=-In-=SUB=-y-=/SUB=-Ga-=SUB=-1-x-y-=/SUB=-P-=SUB=-z-=/SUB=-As-=SUB=-1-z-=/SUB=-/GaAs для фотоэлектрических преобразователей

Fabrication of CZTS Solar Cells Using Electrodeposition Techniques

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