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Earth‐Abundant Chalcogenide Photovoltaic Devices with over 5% Efficiency Based on a Cu 2 BaSn(S,Se) 4 Absorber
Author(s) -
Shin Donghyeop,
Zhu Tong,
Huang Xuan,
Gunawan Oki,
Blum Volker,
Mitzi David B.
Publication year - 2017
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201606945
Subject(s) - materials science , band gap , chalcogenide , photoluminescence , photovoltaic system , optoelectronics , energy conversion efficiency , copper indium gallium selenide solar cells , annealing (glass) , quantum efficiency , thin film , kesterite , sputtering , nanotechnology , solar cell , metallurgy , ecology , biology , czts
In recent years, Cu 2 ZnSn(S,Se) 4 (CZTSSe) materials have enabled important progress in associated thin‐film photovoltaic (PV) technology, while avoiding scarce and/or toxic metals; however, cationic disorder and associated band tailing fundamentally limit device performance. Cu 2 BaSnS 4 (CBTS) has recently been proposed as a prospective alternative large bandgap (~2 eV), environmentally friendly PV material, with ~2% power conversion efficiency (PCE) already demonstrated in corresponding devices. In this study, a two‐step process (i.e., precursor sputter deposition followed by successive sulfurization/selenization) yields high‐quality nominally pinhole‐free films with large (>1 µm) grains of selenium‐incorporated ( x = 3) Cu 2 BaSnS 4− x Se x (CBTSSe) for high‐efficiency PV devices. By incorporating Se in the sulfide film, absorber layers with 1.55 eV bandgap, ideal for single‐junction PV, have been achieved within the CBTSSe trigonal structural family. The abrupt transition in quantum efficiency data for wavelengths above the absorption edge, coupled with a strong sharp photoluminescence feature, confirms the relative absence of band tailing in CBTSSe compared to CZTSSe. For the first time, by combining bandgap tuning with an air‐annealing step, a CBTSSe‐based PV device with 5.2% PCE (total area 0.425 cm 2 ) is reported, >2.5× better than the previous champion pure sulfide device. These results suggest substantial promise for the emerging Se‐rich Cu 2 BaSnS 4– x Se x family for high‐efficiency and earth‐abundant PV.