Theoretical Investigation of the Absorption Properties of 3,6-Bis(thiophen-2-yl)diketopyrrolopyrrole Derivatives in the Solid State

本研究的目的是对3，6-双(硫代-2-基)二酮基吡咯(TDPP)发色团在薄膜中的吸收特性进行理论研究。最近的研究表明，TDPP染料在固态时的吸收光谱受生色团内酰胺单元上不同取代基的影响很大，而单体染料在溶液中的吸收光谱没有明显的变化。因此，薄膜中不同的吸收特性可以归因于固体中不同的堆积，而这不能用简单的激子理论来解释。因此，本项目的目标是利用包括激子-振动和短程耦合在内的激子理论的扩展来解释导致TDPP染料在固体中不同光学性质的发色间相互作用。此外，还将基于基本态模型对固体吸收光谱进行模拟，以考虑极化效应和色团间电荷转移相互作用。所获得的见解将有助于建立二酮基吡咯(DPP)染料的堆积-结构-性能关系，这类染料在有机电子和光伏领域具有很高的应用潜力。

The aim of this research project is the theoretical investigation of the absorption properties of 3,6-bis(thiophen-2-yl)diketopyrrolopyrrole (TDPP) chromophores in thin films. It has been recently shown that the absorption spectra of TDPP dyes in the solid state are significantly influenced by the different substituents at the lactam units of the chromophores, whereas no changes are observed for the respective monomeric dyes in solution. Thus, the different absorption properties in thin films can be attributed to the different packing in the solid state which, however, cannot be explained based on simple exciton theory. Therefore, the goal of this project is to elucidate the interchromophoric interactions leading to the different optical properties of TDPP dyes in the solid state using an extension of the exciton theory including exciton-vibrational and short-range coupling. In addition, the solid state absorption spectra will be also simulated based on the essential states model to account for polarization effects as well as interchromophoric charge transfer interactions. The gained insights will contribute to establish packing-structure-properties relationships for the class of diketopyrrolopyrrole (DPP) dyes, which exhibit high potential for application in organic electronics and photovoltaics.