Highly Efficient Photo-Induced Charge Separation enabled by Metal-Chalcogenide Interfaces in Quantum-Dot/Metal-Oxide Hybrid Phototransistors.

Quantum dot (QD)-based optoelectronics have received a large amount of interest for the versatile applications due to their excellent photosensitivity, facile solution processability, and the wide range of band gap tunability. In addition, the QD-based hybrid devices which are combined with various high-mobility semiconductors have been actively researched to enhance the optoelectronic characteristics as well as maximize the zero-dimensional structural advantages, such as tunable band gap and high light absorption. However, the difficulty of highly efficient charge transfer between QDs and the semiconductors, and the lack of systematic analysis for the interfaces have impeded the fidelity of this platform, resulting in complex device architectures and unsatisfactory device performance. Here, we report ultra-high detective phototransistors with highly efficient photo-induced charge separation using Sn2S64--capped CdSe QD/amorphous oxide semiconductor (AOS) hybrid structure. The photo-induced electron transfer characteristics at the interface of the two materials were comprehensively investigated with an array of electrochemical and spectroscopic analysis. In particular, the photocurrent imaging microscopy revealed that interface engineering in QD-AOS with chelating chalcometallate ligands cause efficient charge transfer, resulting in photovoltaic-dominated responses over whole channel area. On the other hands, monodentate ligand incorporated QD-AOS based devices typically exhibit limited charge transfer with atomic vibration, showing photo-thermoelectric-dominated responses in the drain electrode area.