Single-step fabrication of quantum funnels via centrifugal colloidal casting of nanoparticle films

Abstract

Centrifugal casting of composites and ceramics has been widely employed to improve the mechanical and thermal properties of functional materials. This powerful method has yet to be deployed in the context of nanoparticles—yet size–effect tuning of quantum dots is among their most distinctive and application-relevant features. Here we report the first gradient nanoparticle films to be constructed in a single step. By creating a stable colloid of nanoparticles that are capped with electronic-conduction-compatible ligands we were able to leverage centrifugal casting for thin-films devices. This new method, termed centrifugal colloidal casting, is demonstrated to form films in a bandgap-ordered manner with efficient carrier funnelling towards the lowest energy layer. We constructed the first quantum-gradient photodiode to be formed in a single deposition step and, as a result of the gradient-enhanced electric field, experimentally measured the highest normalized detectivity of any colloidal quantum dot photodetector.

Solution-processed semiconductors for next-generation photodetectors

“…56 These quantum-funnel photodiodes benefit from improved drift-assisted carrier extraction, yielding MHz 3dB-bandwidths even at zero bias and high detectivity in the near-IR.…”

Chitin Nanofiber Transparent Paper for Flexible Green Electronics

“…Building on these previous efforts, we introduce here a new version of transparent paper made with bottom-up self-assembled ChNF. In particular, our ChNF transparent paper is produced by centrifugal casting [43] of a homogeneous chitin solution, the use of which obviates the need for any additional chemical treatment or coagulation process yet produces a uniform large-area sheet. We also fabricate a typical OLED device on our ChNF transparent paper and show that ChNF transparent papers can viably serve as substrates for flexible green electronics.…”

Correlating Charge‐Carrier Dynamics with Efficiency in Quantum‐Dot Solar Cells: Can Excitonics Lead to Highly Efficient Devices?

“…This energy transfer due to size deviation has also been used for light harvesting in the quantum‐funnel solar cell developed by Kim et al. Higher efficiency is achieved through exciton funnelling due to RET between PbS QDs of different sizes . The energy‐transfer process between the QDs strongly depends on the surface chemistry of the QDs; this has been explained by Hoffman et al .…”