Insight into the Peculiarities of the Excited State Properties in the Series of Novel Donor-acceptor Indolizine-based Systems
Timur Burganov a, Sergey Katsyuba a, Liliya Islamova a, Guzel Fazleeva a, Alexey Kalinin a, Andreas Köhn b
a Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center of RAS, Arbuzov st. 8, 420088 Kazan, Russia
b Institut für Theoretische Chemie - Universität Stuttgart, Germany
Proceedings of Interfaces in Organic and Hybrid Thin-Film Optoelectronics (INFORM)
València, Spain, 2019 March 5th - 7th
Organizers: Natalie Stingelin, Henk Bolink and Michele Sessolo
Poster, Timur Burganov, 075
Publication date: 8th January 2019

Near-infrared (NIR) absorbing/emitting systems nowadays attract considerable attention of the researchers due to their promising applications in secure displays, night-vision goggles, tissue welding, telecommunications, biological imaging and dye-sensitized solar cells (DSCs). Significant results in solar light to electricity power conversion efficiencies (PCEs) up to >12% for organic molecules have been reached in this direction. Pure organic molecules possess lowered cost in contrast to the metal-complexes analogs and broad variety for functionalizations allowing fine-tuning of their photophysical properties. As a rule the systems possess D-π-A architecture and mostly utilize di-/triphenylamine (D/TPA) or indoline fragments as D motifs. However these systems have restricted donor strength because of the non-planar twisted structure of the nitrogen lone pair relative to the π-bridges resulting in reducing electron donation capability into acceptor moiety upon excitation. Recently indolizine-based donors have been found as more efficient donating units [1, 2]. Moreover indolizine-based systems demonstrated intensive electronic absorption/emission up to 700-900 nm revealing themselves as perspective candidates to the role of active layers in DCSs devices or NIR emitting materials [3, 4].

Herein we report on the study of excited state (ES) properties in series of novel recently synthesized indolizine-based systems bearing D-π-A architecture. Using the theoretical approaches based on combinations of density functional theory (DFT), time-dependent DFT (TD-DFT), Møller-Plesset second-order perturbation theory (MP2) and algebraic diagrammatic construction through second order (ADC2) methods, their ground and excited states features have been rationalized. Employing independent mode displaced harmonic oscillator (IMDHO) approximation the spectral features of experimental electronic absorption/emission spectra have been described and interpreted. It was found that the shape of the lowest-energy electronic absorption bands is strongly influenced by vibronic progressions. In particular, it was shown that the most intensive absorption is located nearby 0-0 adiabatic transition. IMDHO could be utilized for the prediction of electronic absorption properties in a wide range of indolizine derivatives toward light-harvesting applications.

The reported study was funded by Russian Science Foundation (project № 18-73-00165), and Timur Burganov (personal ref. 91695570 ) gratefully acknowledges the program of the German Service of Academic Exchange (DAAD).

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