Bay-Extended, Distorted Perylene Esters Showing Visible Luminescence after Ultraviolet Excitation: Photophysical and Electrochemical Analysis

Abstract

Perylene derivatives with a unilaterally and bilaterally extended core show luminescence in the visible wavelength range (500−600 nm) that can be excited by absorption in the ultraviolet range (360−370 nm). This unusual behavior is investigated by means of excitation spectroscopy, cyclic voltammetry, and calculations based on (time-dependent) density functional theory. The results indicate that the extended compounds show promising features for optoelectronic applications and even might be used as fluorescent dyes in lasing. This is supported by nonadiabatic ab initio molecular dynamics. With respect to applications in organic optoelectronic nanostructures, nanofilms were prepared via spin-coating and thermal vapor deposition and demonstrated the formation of excimers. The relationship between the excimer-induced bathochromic shift and the interplanar distance of the molecules opens up the possibility to vary the perceived color of a nanofilm via tempering.

Ultrafast Electronic Energy Transfer in an Orthogonal Molecular Dyad

“…Ultrafast relaxation dynamics following photoexcitation and electronic energy transfer (EET) in molecular systems are not only of fundamental interest 1 but are of significance in light harvesting arrays, 2,3 in OLEDs, 4,5 and in organic photovoltaics. [6][7][8] Förster theory, which requires the calculation of point-or line-dipole interactions, can be used to describe longrange EET.…”

Electroluminescent and Optoelectronic Properties of OLEDs with Bay‐Extended, Distorted Perylene Esters as Emitter Materials

“…Photoluminescence (PL) spectra of nanofilms deviate from the PL spectra of solutions of compounds 1 – 3 , but are very similar to the respective EL spectra (Figure b). As mentioned above, the effects of excimer formation on the PL‐spectra of nanofilms of compounds 1 – 3 were already established and discussed in preceding studies . Consequently, it is reasonable to assume that the same process is responsible for the observed EL‐spectra.…”

“…The emission spectrum can be explained with the formation of excimers. The existence of excimers in nanofilms of compounds 1 – 3 and the relationship of the interplanar distance between the molecules and the resulting excimeric red shift were studied earlier . However, the EL‐spectra demonstrate that one has to take into consideration the effects of excimer formation, when choosing compounds such as 1 – 3 for OLED applications.…”

“…The nanofilms of compounds 1 – 3 are mainly polycrystalline ,[29, 54, 55] but compound 2 is of particular interest, because it can form a glassy liquid crystalline phase with a denser packing after annealing, resulting in a smaller interplanar distance and a more pronounced excimeric red shift in the PL‐spectra …”

“…Recently, perylene derivatives containing helicene fragments in their cores have been of special interest owing to their peculiar properties, among others showing liquid crystalline behavior with minimal side chains due to distortions in the arene core . The electronic and spectroscopic properties of extended perylene derivatives with distorted cores are also noteworthy …”