Hybrid-Size Quantum Dots in Hole Transport Layer Depress Dark Current Density of Short-Wave Infrared Photodetectors
Simin Chen, Huaying Zhong, Xiao Wang, Guangjiu Pan, Haodong Tang, Fan Fang, Jiufeng Wu, Weichao Wang, Lihai Xu, Jun Tang, Junjie Hao, Keyu Zheng, Dan Wu, Zeguo Tang, Lei Zhang, L. H. Cao, Peter Müller‐Buschbaum, Kai Wang, Wei Chen
Abstract
PbS quantum dots (QDs) are promising materials for low-cost short-wave infrared (SWIR) photodetection and imaging applications, owing to their unique optical properties and tunable bandgap. High-performance photodiodes rely on thiol-treated small PbS QDs as the hole transport layer (HTL) due to their suitable band alignment, but they face challenges such as crack formation, which increases dark currents. We develop a crack-free HTL by mixing small-size and large-size QDs. Grazing incidence small-angle X-ray scattering data confirms that the hybrid-size QD HTL is more homogeneous and denser than that made from monosize QDs. Photophysical studies show optimized charge carrier dynamics and energy transfer in the hybrid-size QDs, compared to monosize QDs. The devices based on the hybrid-size QD HTL exhibit a significantly reduced dark current density (392 nA/cm 2 ). Additionally, they show high device performance, including a responsivity of 0.65 A/W, detectivity of 2.4 × 10 12 Jones, and an external quantum efficiency of 65% in the SWIR region, paving the way for high-performance QD-based SWIR photodetectors.