Improved Crystal‐Growth and Emission Gain‐Narrowing of Thiophene/Phenylene Co‐Oligomers

Abstract

Large plate‐like single crystals of several millimeters to ∼ 1 cm in size of organic semiconducting materials are prepared via an improved crystal‐growth technique. The crystals (see Figure) exhibit self‐waveguided amplified spontaneous emission with a relatively small threshold resulting from the excellent optical properties of the crystals, such as high transparency and low light scattering.

Origin of the amplified spontaneous emission from thiophene/phenylene co-oligomer single crystals: Towards co-oligomer lasers

“…Spectral narrowing of the whole PL bands and superlinear increases of their intensities have been reported under intense excitation at room temperature. [6][7][8]12 The drastic behavior observed at 10 K is analogous to that of the SNE at room temperature. Therefore, the superlinear increases in the line intensities are considered to be the origin of the SNE and due to the ASE.…”

“…1, 2 The SNE due to amplified spontaneous emission ͑ASE͒ has been demonstrated from single crystals of thiophene and phenylene oligomers, [3][4][5] and single crystals of thiophene/phenylene co-oligomers. [6][7][8] In addition to the ASE, stimulated resonance Raman scattering has been also observed from the co-oligomer crystals. [9][10][11][12] The single crystals of the co-oligomers in high quality and uniformity allow light propagation in the crystals working as a self-waveguide such as a polariton.…”

“…[6][7][8]12 In order to elucidate those, we have investigated the photoluminescence ͑PL͒ properties of the BP1T crystal at low temperature and elevated temperatures under both weak and intense excitations. At low temperature, we have observed several equidistantly separated sharp PL lines from the BP1T crystal and identified them to vibronic sidebands of the molecules.…”

Photopumped laser oscillation and charge-injected luminescence from organic semiconductor single crystals of a thiophene/phenylene co-oligomer

“…15 The procedures of the crystal growth were also described in detail elsewhere. 16 The charged pressure of the N 2 +H 2 ͑10 mol %͒ growth gas was −18.6 kPa ͑a differential pressure from the atmosphere͒ at room temperature. The temperature of the growth cylinder was maintained at 360°C at the material-loaded position ͑bottom͒ and 300°C at the growth position ͑top͒ during crystal growth ͑about 150 h͒.…”

“…The detailed experimental setup was described in our previous work. 16 Fabrication and measurement of the charge-injected luminescence device were carried out follows. A gold electrode that worked as an anode was thermally deposited in the thickness of 15 nm through a shadow mask on a polished glass substrate.…”