Self-Assembly of Squaraine Dyes: A Thermodynamic Exploration of Aggregation on Device Properties

摘要

Squaraine dyes have been ubiquitous in xerography since the 1970's, and have recently begun to be used as a highly efficient absorbing material in organic photovoltaics. Our group has demonstrated that multiple molecular structures within the squaraine family can be used to generate reasonably efficient devices (～2.7% PCE) with very good short circuit current densities (～ 14 mA cm-2). We characterize and explain how the formation of nanoscale aggregates impacts the bulk device properties. The nanoscale aggregates are controllable through macroscopic processes such as solvent and thermal annealing, and we are using the aggregates as a direct, uniquely specific energetic probe of the bulk heterojunction interface. The impact of this work has potential impact in any field that is working with small molecules, including solar power, the health and imaging industry, and the OLED electronics industry as we endeavor to offer deeper QM reasoning for why these materials aggregate, and how that aggregation will impact their structural and optoelectronic properties.