A study on optoelectronics and spectroscopic properties of TPD:Alq3 heterojunction films for the application of UV sensors

The optoelectronics and spectroscopic properties of N, N-diphenyl-N, N-bis(3-methylphenyl)-1, 1-biphenyl-4.4 diamine: tris (8-hydroxyquinolinate) aluminum (TPD:Alq3) systems were investigated for the application of ultraviolet (UV) sensors. Solution processed spin coating technique was used to deposit the films on quartz and to fabricate the devices on ITO-integrated substrates. Results showed that UV absorption of TPD was improved by its doping with Alq3 acceptor in a 1:2 volumetric ratio, thereby reducing its energy gap from 3.08 eV to 2.95 eV. The electronic transition in TDP was found to be direct forbidden, but changed to direct allowed transition by Alq3 dopant. Larger photocurrent, increased exciton generation and improved UV sensing was achieved for TPD: Alq3 (1:2) based UV detectors compared to that of the TPD-based devices. The signal to noise ratio was increased when Alq3 content was added up to 1:2 volumetric ratio, while it was decreased when higher amount of Alq3 was added.