Substitution of the CdS buffer layer in CIGS thin‐film solar cells

Witte, Wolfram; Spiering, S.; Hariskos, Dimitrios

doi:10.1002/vipr.201400546

Cited by 59 publications

(29 citation statements)

References 25 publications

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“…[ 30 ] Zn-compound buffer layers exhibit wider band gaps and therefore less light absorption than CdS, which should lead to higher current densities of solar cells. Most CBD recipes for Zn-compound buffers follow a deposition route very similar to CdS as seen in [ 81 ] Copyright 2014, Wiley-VCH. thiourea as sulfur source and ammonia are mixed together, and the deposition temperature is typically 60-80 °C.…”

Section: Chemical Bath Deposition Of Cds and Zn(sooh)mentioning

confidence: 98%

“…[ 80 ] A number of review papers comprehensively describe the deposition of buffer layers by CBD, atomic layer deposition (ALD), ion-layer gas reaction (ILGAR), ultrasonic spray pyrolysis (USP), metal organic chemical vapor deposition (MOCVD), ED, sputtering and evaporation (PVD). [ 79,[81][82][83][84] The "soft" non-vacuum methods prevail because they offer a conformal and uniform deposition of thin (30-100 nm) layers on the rough absorber surface without the concern of plasmainduced damage as in the case of sputtering. In the following three sub-sections we will review three solution approaches proven to yield high-effi ciency CIGS devices.…”

Section: Buffer Layermentioning

confidence: 99%

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All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

Romanyuk

Hagendorfer

Stücheli

et al. 2014

Adv Funct Materials

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Solution processing of inorganic thin fi lms has become an important thrust in material research community because it offers low-cost and high-throughput deposition of various functional coatings and devices. Especially inorganic thin fi lm solar cells -macroelectronic devices that rely on consecutive deposition of layers on large-area rigid and fl exible substrates -could benefi t from solution approaches in order to realize their low-cost nature. This article critically reviews existing deposition approaches of functional layers for chalcogenide solar cells with an extension to other thin fi lm technologies. Only true solutions of readily available metal salts in appropriate solvents are considered without the need of pre-fabricated nanoparticles. By combining three promising approaches, an air-stable Cu(In,Ga)Se 2 thin fi lm solar cell with effi ciency of 13.8% is demonstrated where all constituent layers (except the metal back contact) are processed from solutions. Notably, water is employed as the solvent in all steps, highlighting the potential for safe manufacturing with high utilization rates. remarkable improvements in conversion effi ciency. [ 1 ] The highest effi ciency of 21.0% has been achieved for two thin fi lm technologies so far: Cu(In,Ga)Se 2 (CIGS) [ 2 ] and CdTe. [ 3 ] Remarkably, both CIGS and CdTe records are exceeding the highest value of 20.4% for the market leading polycrystalline silicon wafer technology. Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells are often considered as low-cost alternatives to CIGS and CdTe because they consist of only earth-abundant and nontoxic elements although the effi ciency is currently limited to 12.6% (12.7% not certifi ed). [ 4 ] Well-established dye-sensitized solar cell (DSSC) and amorphous silicon (a-Si) technology peak at 12.3% and 13.4%, respectively. [ 1 ] The most recent boom in TFPV -organometallic halide perovskite cells -has shown an incredible spurt by advancing effi ciency from below 5% to 17.9%(!) within just 3 years. [ 5 ] On the border to classical TFSC is the thin crystalline silicon technology that employs liftoff of 50-micrometer-thick Si wafers to yield up to 21.2%-efficient solar cells. [ 6 ] These massive research and development efforts in the fi eld of TFSC clearly refl ect their commercial value for manufacturing inexpensive effi cient solar modules -rigid or fl exible. Functional layers for the high effi ciency devices are deposited mostly in a batch-to-batch manner using vacuum-based methods such as evaporation, sputtering, or chemical vapor deposition. For example, Figure 1 exhibits a cross-section of a >20% effi cient CIGS solar cell in the so-called substrate confi guration, where 5 out of 6 functional layers are deposited by evaporation or sputtering. In this respect, non-vacuum deposition methods are often promoted as alternative approaches to reduce capital investment costs, offer fast roll-to-roll (R2R) processing and eventually reduce the PV module prices. Particularly desirable among non-vacuum approaches are solutionb...

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Section: Chemical Bath Deposition Of Cds and Zn(sooh)mentioning

confidence: 98%

Section: Buffer Layermentioning

confidence: 99%

All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

Romanyuk

Hagendorfer

Stücheli

et al. 2014

Adv Funct Materials

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“…This buffer layer serves as the n portion of the p-n junction and typically has a thickness of 0.05-0.1 μm [16]. CdS is a good choice for this buffer layer because it has a bandgap of 2.4 eV, which allows a majority of photons to pass through to the Cu(InGa)Se 2 absorber layer [19]. Only photons with a wavelength shorter than 500.0 nm can be absorbed by the CdS layer.…”

Section: N-cds/cu(inga)se 2 Solar Cell Designmentioning

confidence: 99%

“…ZnO has a bandgap of 2.8 eV, which increases the wavelength spectrum that passes through the buffer layer into the absorber layer [19]. Despite the promise of ZnO buffer layers, many studies demonstrated that using ZnO in place of CdS results in a cell with a 3-5% lower efficiency [16].…”

Section: Developments In Cu(inga)se 2 Designmentioning

confidence: 99%

Design and Optimization of Copper Indium Gallium Selenide Thin Film Solar Cells

Katzman¹

2015

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to ABSTRACT (maximum 200 words)The objective of this thesis was to simulate a new way to create high efficiency Copper Indium Gallium Selenide (Cu(InGa)Se 2 ) cells. This was accomplished by creating a model in Silvaco's technology computer aided design ATLAS program. A baseline model was tested to confirm functionality of the software, and a stepwise approach was used to include additional features. The first addition was the inclusion of a multi-layer absorber layer with graded Ga concentrations. This layer showed increased internal electric fields, which helped to increase the output of the cell. This was followed by the replacement of the traditional n-type CdS buffer layer with a n-type ZnO buffer layer. The ZnO buffer layer was found to have better band alignment than CdS and resulted in a significant improvement in device performance. Finally, a top grid was included which reduced the output of the cell as a result of shading. The final simulation resulted in a Cu(InGa)Se 2 cell which operated at 21.14% efficiency, a 21.9% increase from the baseline cell. SUBJECT TERMS

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“…These costs could be eliminated if a Cd‐free buffer material could be identified, which can be deposited by means of vacuum techniques. A promising candidate is indium sulfide (In

_{x}

_{y}

) as it can be deposited by physical vapor deposition (PVD) ().…”

Section: Introductionmentioning

confidence: 99%

Anomalous temperature dependence of the open‐circuit voltage of InS‐buffered Cu(In,Ga)(Se,S) solar cells simulated in broad temperature range

Schulz

Eraerds²,

Richter

et al. 2015

Physica Status Solidi (a)

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We investigated an open‐circuit voltage phenomenon of Cu(In,Ga)(Se,S)2 thin‐film solar cells observed by device simulations which is manifested in an anomalous temperature dependence (meaning deviating from the linear dependence caused by the temperature dependence of the saturation current) induced by a variation of the buffer electron affinity. In order to study the origin of this effect, we performed simulations of temperature‐dependent current–voltage characteristics while we separately consider thermionic emission and the classical drift‐diffusion model as the decisive charge carrier transport across the hetero‐interfaces. The anomalous open‐circuit voltage phenomenon is in general an electrostatic effect caused by accumulated negative charge at the window/buffer interface created by photo‐generated electrons within the buffer, which partially reach the i‐ZnO layer. This results from a suppress electron transport from the window to the buffer layer. This electron accumulation induces an additional electric field which hinders the elevation of the hole quasi‐Fermi energy within buffer and absorber layer and therefore increases the quasi‐Fermi level splitting which finally leads to an increased open‐circuit voltage. In total, we identified three different temperature regimes for the open‐circuit voltage and will explain its origin in this work.

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Substitution of the CdS buffer layer in CIGS thin‐film solar cells

Cited by 59 publications

References 25 publications

All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

Design and Optimization of Copper Indium Gallium Selenide Thin Film Solar Cells

Anomalous temperature dependence of the open‐circuit voltage of InS‐buffered Cu(In,Ga)(Se,S) solar cells simulated in broad temperature range

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