Engineered copper oxide nanostructure for high-performance visible-light photodetector

Abstract

A visible light photodetector is an essential optoelectronic device for conventional application such as digital imaging, flame detection, and environmental research. Also, recently, it has attracted great interest for new-generation application such as flexible and transparent electronics due to its wide utilization. Copper oxide (CuO) has been considered to be highly suitable as a light absorbing material for visible light detection due to its narrow band gap, cost effectiveness, and easy fabrication. However, research about CuO photodetector is still an early stage, resulting in a lack of theoretical understanding and insufficient performance. In this research, we performed theoretical and experimental studies about CuO visible light photodetectors. First, we newly proposed grain-structure model to investigate the photodetection mechanism, and predicted the effect of grain structure on the optoelectronic property. Then, in order to verify the proposed model experimentally, we fabricated grain structure engineered CuO nanofilm photodetectors and evaluated the optoelectronic performance. We achieved 18 times and 50 times enhanced responsivity and detectivity, respectively, with the largest grain size and reduced contacting size between adjacent grains, as compared with the smallest grain based film. Also, the response speed was significantly improved with increasing the grain size. Moreover, in order to achieve further improved performance, we demonstrated CuO nanowire array photodetectors. The nanowire photodetector showed significantly suppressed dark current due to its 1 dimensional (1D) confined channel and had superior optoelectronic performances

high responsivity of 21.0 A/W and detectivity of $8.89×10^{11}$ Jones, and fast rising and decaying response speeds of 0.329 s and 1.21 s, respectively. We believe that the proposed grain and nanowire based nano-structural engineering method can pave a way for high performance visible light photodetector.