Optically and electrically excited emissions from organic semiconducting oligomer crystals

Abstract

This paper reviews optically and electrically excited emissions from organic semiconducting oligomers in the form of their single crystals. Of the semiconducting oligomers, the review focuses on thiophene/phenylene co-oligomers (TPCOs). The topics cover crystal growth and laser oscillation along with related spectrally narrowed emissions of TPCO crystals. Aside from the strong excitation with a laser beam, weak excitation using a mercury lamp produces optical fringes superimposed on broadband emission spectra. The laser oscillation spectra accompanied by longitudinal multimode and optical fringes observed from the weak excitation have the same origin. This enables us to determine optical constants (i.e. refractive indices) and their dispersion of the crystals and provides sufficient information for the construction of optoelectronic devices based on the organic crystals. As a typical example, the review outlines the improved device constitution and performance as well as device operation methods with light-emitting field-effect transistors (LEFETs), because the device configuration is suited for cutting-edge devices including lasers. Finally the review presents device performance of LEFETs having a diffraction grating. These devices are suited for exploring the possibility of constructing a next-generation current-injected laser device.

Organic Single‐Crystalline Semiconductors for Light‐Emitting Applications: Recent Advances and Developments

“…e) Spectra of typical laser oscillation from TPCO crystals with a desired full‐color emission and their structural formulae. Reproduced with permission . Copyright 2016, The Author, published by John Wiley & Sons on behalf of Society of Chemical Industry.…”

“…Among them, organic single‐crystalline semiconductors (OSCSs) constructed by π‐conjugated molecules in long‐range periodic order have emerged as a unique optoelectrical material . Their defined structures provide an opportunity to investigate the impact of the basic molecular interactions on the structure–property relationships and reveal fundamental physics in organic semiconductors.…”

“…The surface charge transport of these materials was determined based on the technology of field‐effect transistors with recorded mobility reaching up to 43 cm 2 V −1 s −1 . Later, they have emerged as a hotspot in the field of optically pumped lasers, which stemmed from the discovery of amplified spontaneous emission (ASE) phenomena and lasing oscillations . Also, electroluminescent (EL) devices based on organic semiconductors date back to 1963 when the first used materials were also OSCSs .…”

“…This enthusiasm for the study of OSCSs has extended the applications range to various high‐performance and low‐cost optoelectronic devices. A series of broad reviews highlighting the most important progress obtained by OSCSs has finished in different aspects including growth strategies, materials design, and device applications . However, none of the reviews so far has focused on the electrical‐pumping light‐emitting behavior, which is not only scientifically important but also technologically imperative for EL devices.…”

“…[22][23][24] Among them, organic single-crystalline semiconductors (OSCSs) constructed by -conjugated molecules in longrange periodic order have emerged as a unique optoelectrical material. [25][26][27][28][29][30][31][32][33][34][35] Their defined structures provide an opportunity to investigate the impact of the basic molecular interactions on the structure-property relationships and reveal fundamental physics in organic semiconductors. Also, the additional features of OSCSs, such as low impurity levels, high carrier mobility, and high thermal stability, make them more attractive in the field of optoelectronics.…”