Jack Lawton

Advisor: Prof. Correa-Baena

will propose a doctoral thesis entitled,

Vapor Phase Processing of Organic and Hybrid Organic-Inorganic Materials for Perovskite Optoelectronics

On

Monday, December 8th at 11:00 a.m.  

Pettit Microelectronics Building Room 102A

Committee
Professor Juan-Pablo Correa-Baena, Advisor, MSE and Chemistry

Professor John R. Reynolds, Chemistry and MSE

Professor Lauren Garten, MSE

Professor Guoxiang Hu, MSE

Professor Mark Losego, MSE

Abstract

Lead halide perovskites (LHPs) have the potential to revolutionize modern optoelectronics, and they have emerged as key materials for several applications including photovoltaics, light-emitting diodes, and photodetectors. However, scaling the manufacture of these materials is limited by the fact that most research relies on non-scalable deposition methods such as spin coating. Vapor-based deposition techniques, such as thermal evaporation, offer a route to scalable LHP processing by allowing uniform and large-area film deposition without processing solvents.

This thesis will deepen our understanding of how thermal evaporation influences the structure of separate layers within LHP device stacks. Chapter 1 investigates how molecular functionalization influences the thermal stability of organic semiconductors and hence their suitability for thermal evaporation. We focus on phosphonic acid (PA)-functionalized naphthalene diimide (NDI), where NDI is a widely used electron-transport material, and PAs are commonly used anchoring groups. We show, by comparing solution processed and evaporated films, that chemical changes occur during evaporation. These results demonstrate the importance of considering thermal stability when designing molecules for such applications. Chapter 2 will focus on controlling the phase composition of flash-evaporated LHP thin films. Here, we propose that secondary phase formation can be suppressed through phosphonic acid additives that bind strongly to organic precursors, influencing evaporation dynamics. Chapter 3 will focus on thermally evaporated interlayers to suppress halide migration across interfaces. We propose the use of bulky organic cations and identify molecular design routes to control halide migration across interfaces without hindering charge transport.