THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING 

GEORGIA INSTITUTE OF TECHNOLOGY   

Under the provisions of the regulations for the degree
 

DOCTOR OF PHILOSOPHY
 

on Wednesday, April 28, 2021

9:30 AM

via 

BlueJeans Video Conferencing 

https://bluejeans.com/687308766

will be held the 

DISSERTATION PROPOSAL DEFENSE

for 

Gill Biesold-McGee

  “Continuous production and improved stabilities of luminescent colloidal perovskite nanocrystals as next-generation emitters”   

Committee Members: 

Prof. Zhiqun Lin, Advisor, MSE

Prof. Vladimir Tsukruk, MSE

Prof. Juan-Pablo Correa-Baena, MSE

Prof. Naresh Thadhani, MSE

Prof. Zhitao Kang, GTRI

Abstract:

Colloidal perovskite nanocrystals have recently garnered much attention due to their outstanding optoelectronic properties. Their high photoluminescence quantum yield, easily tunable emission peak wavelength, narrow full width at half maximum, solution processability, and outstanding defect tolerance have positioned them one of promising candidates as emitters for next-generation lighting and display. In this context, some major challenges remain, namely, stability and production rate. Most perovskite nanocrystals are synthesized in batch reactions that render a lab-scale yield. Yet, for production to meet the needs of widespread applications, continuous manufacturing is highly desirable. Additionally, the ionic nature of perovskite crystals make them easily degraded from many environmental factors. For broad use, strategies to produce perovskite nanocrystals more resilient towards harsh external stimuli are urgently needed.

In the first two projects, the continuous production of perovskite nanocrystals is explored. First, two-dimensional Ruddlesden-Popper (RP) perovskite nanosheets (L2PbX4) are synthesized in via a flow reactor. The effect of precursor flowrate, antisolvent composition, antisolvent flowrate, and reactor tube length are  scrutinized. Optimized parameters yield PEA2PbBr4 and PEA2PbI4 nanoplatelets with comparable optical properties to those form batch methods.

The second project involves the incorporation of a star-like unimolecular block copolymer micelle templates into a flow reactor. These nanoreactors are made by the sequential atom transfer radical polymerization of tert-butyl acrylate and styrene. After hydrolysis of the inner PtBA block to poly(acrylic acid), perovskite precursors selectively coordinate with the hydrophilic inner PAA block. The pre-loaded nanoreactors are then placed in the flow reactor and introduced to an antisolvent, which spurs crystallization of perovskite in the inner block. Simultaneously, the outer PS blocks enable superior colloidal stability due to their permanently attachment to perovskite nanocrystal surface.

The third project aims to increase the stability of two-dimensional RP perovskite nanosheets by engineering the bulky organic cations. Traditionally, the outermost components of the bulky organic cations are hydrophobic tails that enable strong colloidal stability. By creating bulky organic cations with active sites (C=C double bonds and C≡C triple bonds) as the outermost components, they can be functionalized in a variety of ways. Crosslinking between the cations can be done through either direct polymerization or thiol-ene click chemistry. Different functional polymers can be directly grown from the NPL or can be attached via the “graft-to” approach using azide-alkyne chemistry. The diverse functionalities from these organic molecules can impart an amazing array of enhanced stabilities.