Enhancement of the Visible Light Photodetection of Inorganic Photodiodes via Additional Quantum Dots Layers.

Visible light photodetectors are extensively researched with transparent metal oxide holes/electron layers for various applications. Among the metal oxide transporting layers, nickel oxide (NiO) and zinc oxide (ZnO) are commonly adopted due to their wide band gap and high transparency. The objective of this study was to improve the visible light detection of NiO/ZnO photodiodes by introducing an additional quantum dot (QD) layer between the NiO and ZnO layers. Utilizing the unique property of QDs, we could select different sizes of QDs and responsive light wavelength ranges. The resulting red QDs utilized device that could detect light starting at 635 nm to UV (Ultra-violet) light wavelength and exhibited a photoresponsivity and external quantum efficiency (EQE) of 14.99 mA/W and 2.92% under 635 nm wavelength light illumination, respectively. Additionally, the green QDs, which utilized a device that could detect light starting at 520 nm, demonstrated photoresponsivity values of 8.34 mA/W and an EQE of 1.99% under 520 nm wavelength light illumination, respectively. In addition, we used X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) to investigate the origin of the photocurrents and the enhancement of the device's performance. This study suggests that incorporating QDs with metal oxide semiconductors is an effective approach for detecting visible light wavelengths in transparent optoelectronic devices.