5 research outputs found
Small atom doping: a synergistic strategy to reduce SnZn recombination center concentration in Cu2ZnSnSe4
Kesterite Cu2ZnSnS x Se4-x (CZTSSe) is among the most promising inorganic Earth-abundant thin-film photovoltaic technologies, although currently, the larger voltage deficit compared with more mature chalcogenide technologies is hampering solar-to-electricity conversion efficiency progress in these materials. Most of the latest reports agree on the CZTSSe defect structure as the main limitation for the open-circuit voltage. Small atom doping is suggested as an interesting strategy to reduce the concentration of defects without affecting secondary phase formation. Herein, an innovative approach based on the introduction of LiAlH4 and its further decomposition during the selenization process of CZTSe precursors, as a pathway for hydrogen and lithium/alkali transient doping, is explored. This process shows a strong beneficial influence on the crystal growth and solar cell device performance, especially with a significant improvement in V oc and fill factor. A reduction of nonradiative recombination and a remarkable fourfold increase in the carrier lifetime correlating with the reduction of the open-circuit voltage (V oc) deficit below 330ÂżmV is demonstrated. A mechanism on how small atoms (Li and H) interact to reduce the concentration of SnZn recombination centers while keeping doping relatively unchanged is proposed, opening fundamental perspectives for the simple and universal transient doping of thin-film chalcogenide compounds.Peer ReviewedPostprint (published version
Towards low cost and sustainable thin film thermoelectric devices based on quaternary chalcogenides
This is the peer reviewed version of the following article: Isotta, E. [et al.]. Towards low cost and sustainable thin film thermoelectric devices based on quaternary chalcogenides. "ADVANCED FUNCTIONAL MATERIALS", 20 Maig 2022, núm. 2202157, which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/adfm.202202157. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.A major challenge in thermoelectrics (TEs) is developing devices made of sustainable, abundant, and non-toxic materials. Furthermore, the technological drive toward low sizes makes crucial the study of nano and micro configurations. In this work, thin film TE devices based on p-type Cu2+xZn1-xSnS4 and Cu2+xZn1-xSnSe4, and n-type AlyZn1-yO are fabricated by physical vapor deposition. The kesterite phases show good purity and promising TE power factor, likely enhanced by the copper–zinc order–disorder transition. Thin film generators in planar configuration are assembled by a sequential deposition of the p-type, n-type, and contact materials. The power per unit planar area reaches 153 and 279 nW cm-2 for the sulphur- and selenium-based generators, respectively. These values significantly outperform any other literature attempt based on sustainable and low-cost thin films. Furthermore, if compared with traditional TEs often made of scarce and toxic materials, these devices offer a cost reduction above 80%. This allows reaching comparable values of power density per unit material cost, representing a first real step toward the development of sustainable and non-toxic thin film TE devices. These can find applications in micro energy harvesters, microelectronics coolers, and temperature controllers for wearables, medical appliances, and sensors for the internet of things.A.J. thanks the European Social Fund+ for the FI fellowship. The authors
would like to acknowledge the help of Dr. Mirco D’Incau, Dr. Narges
Ataollahi, and Prof. Della Volpe for the design of the measuring setup,
as well as useful discussion with Prof. Dario Narducci. This research has
received funding from the Spanish Ministry of Science, Innovation and
Universities under the MATER-ONE projects (PID2020-116719RB-C41).
Authors from IREC belong to the SEMS (Solar Energy Materials
and Systems) Consolidated Research Group of the “Generalitat de
Catalunya” (ref. 2017 SGR 862) and are grateful to European Regional
Development Funds (ERDF, FEDER Programa Competitivitat de
Catalunya 2007–2013). M.G. acknowledges the financial support from
Spanish Ministry of Science, Innovation and Universities within the Juan
de la Cierva fellowship (IJC2018-038199-I). E.S. acknowledges the ICREA
Academia Program. Open Access Funding provided by Universita degli Studi di Trento
within the CRUI-CARE Agreement.Peer ReviewedPostprint (published version
Challenges and improvement pathways to develop quasi-1D (Sb1-xBix)2Se3-based materials for optically tuneable photovoltaic applications. Towards chalcogenide narrow-bandgap devices
Quasi-1D chalcogenides have shown great promises in the development of emerging photovoltaic technologies. However, most quasi-1D semiconductors other than Sb2Se3 and Sb2S3 have been seldom investigated for energy generation applications. Indeed, cationic or anionic alloying strategies allow changing the bandgap of these materials, opening the door to the development of an extended range of chalcogenides with tuneable optical and electrical properties. In this work, Bi incorporation into the Sb2Se3 structure has been proved as an effective approach to modulate the bandgap between 0.1. In order to better understand the underlying mechanisms leading to the formation of (Sb1-xBix)2Se3, and thus design specific strategies to enhance its properties, thin films with different annealing time and temperature have been synthesized and characterized. Interestingly, it has been observed that Sb2Se3 and Bi2Se3 are formed first, with Bi melting at 300 ÂżC and diffusing rapidly towards the surface of the film. At higher temperature, the binary compounds combine to form the solid solution, however as the dwell time increases, (Sb1-xBix)2Se3 decomposes again into Bi2Se3 and Sb. This study has shown that the material is essentially limited by compositional disorder and recombination via defects. Likewise, routes have been proposed to improve morphology and uniformity of the layer, achieving efficiencies higher than 1% for x > 0.2Postprint (published version
Challenges and improvement pathways to develop quasi-1D (Sb1-xBix)2Se3-based materials for optically tuneable photovoltaic applications. Towards chalcogenide narrow-bandgap devices
Quasi-1D chalcogenides have shown great promises in the development of emerging photovoltaic technologies. However, most quasi-1D semiconductors other than Sb2Se3 and Sb2S3 have been seldom investigated for energy generation applications. Indeed, cationic or anionic alloying strategies allow changing the bandgap of these materials, opening the door to the development of an extended range of chalcogenides with tuneable optical and electrical properties. In this work, Bi incorporation into the Sb2Se3 structure has been proved as an effective approach to modulate the bandgap between 0.1. In order to better understand the underlying mechanisms leading to the formation of (Sb1-xBix)2Se3, and thus design specific strategies to enhance its properties, thin films with different annealing time and temperature have been synthesized and characterized. Interestingly, it has been observed that Sb2Se3 and Bi2Se3 are formed first, with Bi melting at 300ÂşC and diffusing rapidly towards the surface of the film. At higher temperature, the binary compounds combine to form the solid solution, however as the dwell time increases, (Sb1-xBix)2Se3 decomposes again into Bi2Se3 and Sb. This study has shown that the material is essentially limited by compositional disorder and recombination via defects. Likewise, routes have been proposed to improve morphology and uniformity of the layer, achieving efficiencies higher than 1% for x>0.2
Bromine etching of kesterite thin films: perspectives in depth defect profiling and device performance improvement
Using a controlled bromine etching on kesterite absorbers, two major results are obtained. We establish the first defect depth profiling and secondary phases depth profiling of a state of the art Cu2ZnSnSe4 (CZTSe) film by using surface sensitive characterization methods (XPS and Raman spectroscopy) on successively etched samples, obtaining a direct insight on the factors hampering the performance of this class of absorber. In a second step, we demonstrate the possibility of significant improvement to the p-n interface in Cu2ZnGeSe4 (CZGSe)/CdS solar cells when a short bromine etching of the absorber is performed, with the Fill Factor improving by more than 7 points. This method offers a simple improvement pathway for state of the art kesterite devices, with a potentially broader application to thin film solar cells where the p-n interface is limiting.Peer ReviewedPostprint (published version