Water Evaporation Induced Conversion of CuSe Nanoflakes to Cu_2−xSe Hierarchical Columnar Superstructures for High-Performance Solar Cell Applications

Abstract

In this work, a facile and low‐temperature water evaporation approach to prepare columnar superstructures consisting of face centered cubic (fcc) Cu2−xSe nanoflakes stacked along 〈111〉 direction is reported. Formation of such unique stacked nanoflake assemblies is resulted from oriented attachment of isolated hexagonal CuSe nanoflakes along the 〈001〉 direction with a ripening effect driven by solvent evaporation, and then followed by a phase conversion into fcc Cu2−xSe. Evolution from hexagonal CuSe nanoflakes to fcc Cu2−xSe columnar superstructures results in obvious red‐shift of band‐gap absorption edge from 670 to 786 nm and dramatically decreased Raman resonance band intensity of the Se–Se stretching mode at 259 cm−1 due to the phase conversion and composition variation. Remarkably, the Cu2−xSe columnar superstructures are employed as low‐cost and highly efficient counter electrodes (CEs) in quantum dot sensitized solar cells, exhibiting excellent electrocatalytic activity for polysulfide electrolyte regeneration. A ZnSe/CdSe cosensitized solar cell using the Cu2−xSe CE shows a significant increase in fill factor and short‐current density (JSC) and yields a 128% enhancement in power conversion efficiency as compared to the traditional noble metal Pt CE.

Copper Selenides as High-Efficiency Electrocatalysts for Oxygen Evolution Reaction

“…Similar oxidation states of Cu could be assigned for Cu 2 Se (CVD) catalyst as shown in Figure f where peaks at 932.1 and 952.2 eV for Cu 1+ 2p 3/2 and 2p 1/2 peaks and binding energies at 934.2 and 954.4 eV for Cu 2+ 2p 3/2 and 2p 1/2 peaks. These binding energy values nicely matched with previous report of Cu 2 Se. − It should be mentioned that Cu at the surface of both electrodeposited and CVD synthesized Cu 2 Se showed mixed oxidation states of +1 and +2. The coexistence of +1 and +2 mixed valence is well-known in Cu 2 Se .…”

Low temperature crystallization of Cu2ZnSnSe4 thin films using binary selenide precursors

“…Also, it is in good agreement with reported literature [9,11]. The Cu 2 ZnSnSe 4 thin film selenized at temperature 450 °C shows higher band gap of 1.85 eV might be due to the presence of secondary CuSe phase [42] in the film that has reflected in XRD and Raman spectra.…”

Conversion electrochemistry of copper selenides for robust and energetic aqueous batteries

“…As the potential reaches 0.54 V (all potentials in this article are vs. standard hydrogen electrode (SHE), unless otherwise stated), several new diffraction peaks emerge and can be indexed to umangite Cu 3 Se 2 31 . Further discharging to 0.44 V results in the vanishing of the peaks associated with Cu 3 Se 2 and the appearance of three peaks located at 26.9°, 44.8°, and 53.0°, which can be assigned to cubic berzelianite Cu 1.8 Se 32 . At the end of discharge, berzelianite Cu 1.8 Se finally transforms to Cu 2 Se.…”

“…31 Further discharging to 0.44 V results in the vanishing of the peaks associated with Cu 3 Se 2 and the appearance of three peaks located at 26.9°, 44.8°, and 53.0°, which can be assigned to cubic berzelianite Cu 1.8 Se. 32 At the end of discharge, berzelianite Cu 1C). The dominant Raman band at 260 cm −1 , characteristic of hexagonal CuSe, can be assigned to the Se-Se stretching mode of Se 2 dimers.…”