Solution‐Processed Low‐Bandgap CuIn(S,Se)2 Absorbers for High‐Efficiency Single‐Junction and Monolithic Chalcopyrite‐Perovskite Tandem Solar Cells |
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| Authors: | Alexander R. Uhl Adharsh Rajagopal James A. Clark Anna Murray Thomas Feurer Stephan Buecheler Alex K.‐Y. Jen Hugh W. Hillhouse |
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| Affiliation: | 1. Department of Chemical Engineering, Molecular Engineering and Sciences Institute, University of Washington, Seattle, WA, USA;2. Laboratory of Photonics and Interfaces (LPI), école Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland;3. Department of Materials Science and Engineering, University of Washington, Seattle, WA, USA;4. Laboratory for Thin Films and Photovoltaics, Empa – Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland;5. Department of Materials Science and Engineering, Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong |
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| Abstract: | A novel molecular‐ink deposition route based on thiourea and N,N‐dimethylformamide (DMF) that results in a certified solar cell efficiency world record for non‐vacuum deposited CuIn(S,Se)2 (CIS) absorbers and non‐vacuum deposited absorbers with a bandgap of 1.0 eV, is presented. It is found that by substituting the widely employed solvent dimethyl sulfoxide with DMF, the coordination chemistry of InCl3 could be altered, dramatically improving ink stability, enabling up to tenfold increased concentrations, omitting the necessity for elevated ink temperatures, and radically accelerating the deposition process. Furthermore, it is shown that by introducing compositionally graded precursor films, film porosity, compositional gradients, and the surface roughness of the absorbers are effectively reduced and device conversion efficiencies are increased up to 13.8% (13.1% certified, active area). The reduced roughness is also seen as crucial to realize monolithically interconnected CIS‐perovskite tandem devices, where semitransparent MAPbI3 devices are directly deposited on the CIS bottom cell. Confirming the feasibility of this approach, monolithic devices with near perfect voltage addition between subcells of up to 1.40 V are presented. |
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| Keywords: | CIGS CIS low‐bandgap perovskites tandem solar cells |
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