Butterfly‐Shaped Thiophene‐Pyridine Hybrids: Green Electroluminescence and Large Third‐Order Optical Nonlinearities

• Published in: ChemPlusChem (Weinheim, Germany) Vol. 85; no. 8; pp. 1762 - 1777
• Main Authors: Kakekochi, Viprabha, Gangadharappa, Sathish Chatnahalli, Nikhil, P. P., Chandrasekharan, Keloth, Darshan, Vibhu, Narayanan Unni, K. N., Dalimba, Udaya Kumar
• Format: Journal Article
• Language: English
• Published: 01-08-2020
• Subjects: electroluminescence; light-emitting diodes; nonlinear optics; photophysics; thiophenes
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.202000435

A set of four symmetric, butterfly‐shaped 4‐(4‐(decyloxy)phenyl)‐2,6‐di(thiophen‐2‐yl)pyridine (TPY) derivatives 2TPA‐TPY (TPY center and triphenylamine end groups), 2CBZ‐TPY (TPY center and N‐ethyl carbazole end groups), 2TPY‐TPA (triphenylamine center and TPY at the periphery) and 2TPY‐CBZ (N‐ethyl carbazole center and TPY at the periphery) was synthesized. The molecules show reverse saturable absorption (RSA) which is consistent with two‐photon absorption (2PA) associated with excited‐state absorption (ESA) when excited using a 532 nm laser beam. The molecules 2TPA‐TPY and 2TPY‐TPA possess extremely low limiting thresholds of 1.73 and 2.68 J cm−2, respectively. An organic light‐emitting diode (OLED) fabricated from 2TPA‐TPY exhibits green emission with a maximum luminance of 207 cd m−2, a current efficiency (ηCE) of 1.51cd A−1, a maximum power efficiency (ηPmax) of 0.46 lm W−1 and an external quantum efficiency (ηEQE) of 0.48 % at 100 cd m−2.
Butterfly effect: An ambipolar butterfly‐shaped 4‐(4‐(decyloxy)phenyl)‐2,6‐di(thiophen‐2‐yl)pyridine derivative (2TPA‐TPY) acts as a green emitter for non‐doped OLEDs exhibiting an external quantum efficiency (ηEQE) of 0.48 % at 100 cd m−2. Furthermore, it shows enhanced two‐photon absorption properties and extremely low optical limiting with a threshold of 1.73 J cm−2.