Joint Seminar by SKL, SID and ECE Department - Nano-printing Colloidal Nanocrystal Optoelectronics

Colloidal nanocrystals (NCs), including semiconducting quantum dots (QDs), have emerged as a cornerstone material platform for next-generation optoelectronics, offering size-tunable optical properties, solution-processability, and seamless integration with diverse device architectures. Fully unlocking the potential of these nanomaterials requires a holistic approach spanning material synthesis, multi-scale fabrication, and device design. While NCs serve as ideal inks for the additive manufacturing of customized device structures, the development of printed optoelectronics is historically bottlenecked by constrained ink properties, multi-layer processing incompatibilities, and prohibitive post-processing temperatures. Consequently, fully printed, sophisticated heterojunctions capable of efficient photocarrier collection remain exceptionally rare.

In this talk, I will introduce our recent breakthrough in the synthesis of Indium Antimonide (InSb) QDs, where we decoupled nucleation and growth stages to isolate and investigate their reaction dynamics. This strategy extends the absorption peak of InSb QDs from 1400 nm to over 2500 nm, enabling high-performance extended short-wavelength infrared (eSWIR) responsivity. Next, I will focus on a nano-resolution printing methodology developed by our group that seamlessly deposits a library of colloidal NC inks, followed by an in situ, room-temperature ligand exchange to functionalize the NC solids. This versatile strategy enables layer-by-layer printing across a broad palette of NC inks, ligand reagents, substrates, and device architectures. We elucidate the underlying printing mechanisms and investigate passive droplet deflection on heterogeneous surfaces through coupled simulations and experiments. This optimization yields printed Ag NC structures featuring sub-100 nm linewidths and bulk-like conductivity. By leveraging Ag, Au, ZnO, and PbS NCs with compact ligands, we demonstrate fully printed, multi-layer infrared photodiodes with 10-μm pixel sizes. Finally, I will highlight how we translate these material and fabrication breakthroughs to the system level. By designing QD-based photosensitive capacitors integrated with Si readout circuits, we showcase a prototype for retinomorphic, event-based SWIR imagers. Together, these advancements establish a scalable, low-temperature paradigm for developing next-generation intelligent vision systems.