Izaki Masanobu, Abe Suzuka, Nakakita Kota, Khoo Pei Loon
Graduate School of Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi-shi, Aichi 441-8580, Japan.
ACS Omega. 2021 Oct 8;6(41):27587-27597. doi: 10.1021/acsomega.1c05163. eCollection 2021 Oct 19.
CuO/CuO bilayers were fabricated by electrodeposition of the CuO layer in a copper(II)-ammonia complex aqueous solution, followed by photoelectrochemical deposition of the CuO layer at potentials ranging from -0.3 to -1.0 V referenced to a Ag/AgCl electrode in a copper(II)-lactate complex aqueous solution under light irradiation, and the effects of varied potentials of the photoelectrochemical CuO depositions and post-heating conditions on their structural, optical, and photovoltaic characteristics were investigated with X-ray diffraction, field emission-scanning electron microscopy, optical absorption measurements, and external quantum efficiency (EQE) measurements with and without applied bias voltage. The CuO layers with a characteristic 2.1 eV band gap energy were adhesively stacked on the thorn-like grains of the CuO layers possessing a characteristic 1.5 eV band gap energy, and dense and defect-free CuO/CuO bilayers could be fabricated at the potentials of -0.4 and -0.5 V, but the grain size of CuO decreased at -0.5 V. In addition, the metallic Cu was deposited simultaneously at potentials less than -0.7 V. The CuO/CuO bilayer fabricated at -0.4 V revealed photovoltaic features at wavelengths ranging from 350 nm to approximately 900 nm, and a maximum EQE value of 56.8% was achieved at 510 nm in wavelength with a bias voltage of -0.1 V. The maximum EQE value, however, decreased to 1.2% accompanied with the peak wavelength shift to 580 nm, and no photovoltaic feature was observed at potentials of -0.3, -0.7, and -1.0 V. The photovoltaic performance for the CuO/CuO bilayer fabricated at -0.4 V was ameliorated by heating at 423 K, and the maximum EQE values were enhanced to 87.7% at 550 nm and 89.8% at 530 nm in an ambient atmosphere and vacuum. Both the CuO and CuO layers acted as photovoltaic layers in the CuO/CuO bilayer fabricated at -0.4 V and heated at 423 K, and the electrical characteristic including the carrier mobility affected the photovoltaic performance. The photovoltaic feature, however, disappeared by heating above 523 K due to the formation of nanopores inside the CuO layer and near the CuO heterointerface to the CuO and fluorine-doped tin oxide substrate.
通过在铜（II）-氨络合物水溶液中电沉积CuO层，随后在光照下于乳酸铜（II）络合物水溶液中相对于Ag/AgCl电极在-0.3至-1.0V的电位范围内进行CuO层的光电化学沉积，制备了CuO/CuO双层结构。利用X射线衍射、场发射扫描电子显微镜、光吸收测量以及有无施加偏置电压下的外量子效率（EQE）测量，研究了光电化学CuO沉积的不同电位和后热处理条件对其结构、光学和光伏特性的影响。具有特征性2.1eV带隙能量的CuO层粘结堆叠在具有特征性1.5eV带隙能量的CuO层的刺状晶粒上，在-0.4V和-0.5V的电位下可以制备出致密且无缺陷的CuO/CuO双层结构，但在-0.5V时CuO的晶粒尺寸减小。此外，在小于-0.7V的电位下会同时沉积金属Cu。在-0.4V制备的CuO/CuO双层结构在350nm至约900nm的波长范围内表现出光伏特性，在波长510nm、偏置电压为-0.1V时实现了56.8%的最大EQE值。然而，最大EQE值降至1.2%，同时峰值波长移至580nm，在-0.3V、-0.7V和-1.0V的电位下未观察到光伏特性。在-0.4V制备的CuO/CuO双层结构在423K下加热后光伏性能得到改善，在环境气氛和真空中，最大EQE值在550nm时提高到87.7%，在530nm时提高到89.8%。在-
