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

Abstract

Three esters with a perylene, a unilaterally, and a bilaterally extended perylene core, respectively, were used as emitter materials for organic light-emitting diodes. The electroluminescent properties of these devices were studied. Different spectral shifts were found, which can be attributed to the formation of excited dimers (excimers) in the nanofilms of the emitter materials. Thermal treatment of the unilaterally extended derivative resulted in a red-shift of the electroluminescence owing to the formation of a denser nanofilm. The luminance and efficiency of optoelectronic devices employing the extended perylene esters exceed those of devices using an emitter layer comprised of the perylene ester. Different deposition methods, limitations in the deposition process, and the role of hole-transporting materials are compared.

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance

“…For practical applications of semitransparent solar cells, the color coordinates ( x , y ) of a semitransparent solar cell are calculated from the transmitted light, which is expressed as the product of the incident light spectrum and the transmission spectrum of the device. Figure a shows the standard illuminant D65 and AM 1.5G solar spectrum, which are typically selected as the reference light source/incident light to determine the color parameters of a semitransparent solar cell.…”

“…a) Color coordinates of Illuminant D65 and AM 1.5G light in CIE xy 1931 chromaticity diagram. Reproduced with permission . Copyright 2017, Wiley.…”

Organic Light‐Emitting Diodes Based on a Columnar Liquid‐Crystalline Perylene Emitter

“…[24][25][26] The use of perylene derivatives in OLEDs has been explored by several groups, however, most studies primarily focused on physicochemical properties of materials and their potential applications rather than device performance and characteristics. Hence, emitters were only incorporated in simple OLED structures which often required drive voltages >8 V and achieved a maximum luminance of mostly <1000 cd m −2 at voltages higher than 10 V, [27][28][29][30][31] similar to other studies of liquid crystal-based OLEDs. [17,[32][33][34][35] In order to develop more efficient liquid crystalline OLEDs, the knowledge about the self-assembling properties of DLCs that the community has acquired over the past decades needs to be appropriately integrated with state-of-the-art OLED structures and with the functional materials used in these.…”

“…Measurement of TDM orientation via angle-resolved p-polarized PL spectra fitted to a transfer matrix model as described in literature [1][2][3]6,9] revealed a preferential horizontal orientation of the transition dipoles with an anisotropy of a = 0.1 (a denotes the ratio of vertical dipoles over all dipoles; a = 0 for complete horizontal orientation and a = 0.33 for isotropic orientation; Figure 1c; Figure S1, Supporting Information). Since annealing of liquid crystalline materials may lead to denser packing and improved structural order, [29] we also studied the TDM orientation for heated films. For annealing temperatures up to 120 °C only minor changes were observed, but annealing to 160 °C and above caused slight narrowing of the PL spectra and molecular re-orientation (Figure 1b,c).…”

“…Although detailed studies of the compound in both solution and thin film were made previously, key photophysical quantities such as photoluminescence quantum yield (PLQY) and TDM anisotropy remain unknown. [22,29,36,37] Here, we investigate the photophysical properties of PTCTE thin films by measurements of PLQY, TDM orientation, and emission behavior upon annealing. In order to improve PLQY and OLED efficiency, we then incorporated the emitter into different host materials and implemented the host-guest-films into state-of-the-art OLED structures.…”