Efficient charge carrier separation and excellent visible light photoresponse in Cu2O nanowires

• Published in: Nano energy Vol. 50; pp. 118 - 125
• Main Authors: Zhou, Tingwei, Zang, Zhigang, Wei, Jing, Zheng, Junfeng, Hao, Jiongyue, Ling, Faling, Tang, Xiaosheng, Fang, Liang, Zhou, Miao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2018
• Subjects: Carrier separation; Cu2O nanowire; First-principles; Photodiode; Tunable electronic structure; Tunable electronic structure; Carrier separation; Photodiode; Cu2O nanowire; First-principles
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2018.05.028

Last decade has witnessed a surge of research pertaining to Cu2O nanowires for fields of photocatalysts, sensors, solar cells and rechargeable battery systems owing to their unique physicochemical properties. Their atomic properties, especially the size dependent electronic structures, however, remain unknown. Herein, by combining systematic first-principles calculations with material synthesis, characterization, device fabrication and measurement, we investigated physical properties of Cu2O nanowires and their applications in visible light photodiodes. We explored Cu2O nanowires with triangular and hexagonal cross sections of a series of diameter size, and found that they have favorable formation energies, indicative of facile synthesis. These nanowires have tunable direct band gap ranging from 2.2 to 5.4 eV, and a simple model is derived to effectively predict gap size. Remarkably, obvious spatially separated charge distribution of conduction and valance band edges was observed, ensuring long lifetime of excited electron-hole pairs that may greatly benefit performance of optoelectronic devices. Experimentally, we synthesized well-crystallized Cu2O nanowires and fabricated photodiodes, which exhibit a fast rise time of 9.86 ms, decay time of 27.37 ms, and high responsivity of 10 A/W. We expect these results to shed new light on Cu2O nanostructures for scalable, versatile and high-performance optoelectronic devices. The atomic electronic structures of Cu2O nanowires were investigated by combining systematic first-principles calculations with material synthesis, characterization, device fabrication and performance measurements. These nanowires exhibit tunable band gap, efficient carrier separation, and excellent visible light photoresponse. [Display omitted] •For the first time, Cu2O nanowires of different size have been systematically investigated by first-principles calculations.•Cu2O nanowires have favorable formation energies, and exhibit direct band gap with tunable gap size ranging from 2.2 to 5.4 eV.•Obvious spatially separated charge distribution of VBM/CBM is observed, ensuring long lifetime of excited electron-hole pairs.•High-performance photodiodes based on Cu2O nanowires were fabricated, which exhibit very high responsivity.