Insight Into the Optoelectronic Properties of 2,1,3-Benzoxadiazole Based Small Organic Molecules

The development of solution-processed small molecules for organic optoelectronics remains an urgent research task. Herein, the study of the opto-electrical properties of conjugated small molecules of 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) in thin films is reported. These small molecules exhibited an absorption maximum at around 347 nm, as expected for electronic transitions of the π – π * type, an optical band gap of 2.74 eV, and strong PL emission located in the red region. The energy levels of lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) were determined by cyclic voltammetry. Because Ohm's law was dominant at low voltages, space charge-limited conduction (SCLC) following trap-controlled SCLC at higher applied voltages was observed from current–voltage characteristics analysis. The charge carrier mobility was assessed to be 9.64 × 10^ - 5 cm^2V^ - 1s^ - 1 . Mott-Schottky measurements were also performed.