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Phase Conversion from Hexagonal CuSySe1–y to Cubic Cu2–xSySe1–y: Composition Variation, Morphology Evolution, Optical Tuning, and Solar Cell Applications
journal contribution
posted on 2014-09-24, 00:00 authored by Jun Xu, Xia Yang, Qingdan Yang, Wenjun Zhang, Chun-Sing LeeIn this work, we report a simple
and low-temperature approach for
the controllable synthesis of ternary Cu–S–Se alloys
featuring tunable crystal structures, compositions, morphologies,
and optical properties. Hexagonal CuSySe1–y nanoplates and face centered
cubic (fcc) Cu2–xSySe1–y single-crystal-like
stacked nanoplate assemblies are synthesized, and their phase conversion
mechanism is well investigated. It is found that both copper content
and chalcogen composition (S/Se atomic ratio) of the Cu–S–Se
alloys are tunable during the phase conversion process. Formation
of the unique single-crystal-like stacked nanoplate assemblies is
resulted from oriented stacking coupled with the Ostwald ripening
effect. Remarkably, optical tuning for continuous red shifts of both
the band-gap absorption and the near-infrared localized surface plasmon
resonance are achieved. Furthermore, the novel Cu–S–Se
alloys are utilized for the first time as highly efficient counter
electrodes (CEs) in quantum dot sensitized solar cells (QDSSCs), showing
outstanding electrocatalytic activity for polysulfide electrolyte
regeneration and yielding a 135% enhancement in power conversion efficiency
(PCE) as compared to the noble metal Pt counter electrode.