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Direct Identification of Antisite Cation Intermixing and Correlation with Electronic Conduction in CuBi2O4 for Photocathodes

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posted on 17.09.2020, 20:19 by Hyun Joon Jung, Younghwan Lim, Byeong-Uk Choi, Hyung Bin Bae, WooChul Jung, Sangwoo Ryu, Jihun Oh, Sung-Yoon Chung
Cu-based p-type semiconducting oxides have been sought for water-reduction photocathodes to enhance the energy-conversion efficiency in photoelectrochemical cells. CuBi2O4 has recently attracted notable attention as a new family of p-type oxides, based on its adequate band gap. Although the identification of a major defect structure should be the first step toward understanding the electronic conduction behavior, no direct experimental analysis has been carried out yet. Using atomic-scale scanning transmission electron microscopy together with chemical probing, we identify a substantial amount of BiCu–CuBi antisite intermixing as a major point-defect type. Our density functional theory calculations also show that antisite BiCu can seriously hinder the hole-polaron hopping between Cu, in agreement with lower conductivity and a larger thermal activation barrier under a higher degree of intermixing. These findings highlight the value of the direct identification of point defects for a better understanding of electronic properties in complex oxides.

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