Effect of donor on the performance of self-powered UV photodiodes based on solution-processed TPD:Alq3 and NPD:Alq3 active layers

Abstract

In this work, the impact of donor material on the optical and photodiode response is revealed by comparing the performance of self-powered photodiodes based on D:Alq3 (D=TPD or NPD) composite. The active layers were fabricated from solution-processed composites using the well-known spin coating technique, followed by their optical and electrical characterizations. The photodiodes were utilized for the UV light detection in a self-powered mode, in which no external power is required, but it is generated through the photovoltaic effect. Results showed that the NPD film has provided a broader and more intensive optical absorption towards the UV light compared to that of TPD. Also, photoluminescence quenching in the NPD:Alq3 composite was found to highly outperform that of the TPD:Alq3. These were ascribed to the effect of extra pi conjugated bonds present in the NPD, which are originated from the aromatic rings. Consequently, the NPD:Alq3 photodiodes presented a respective sensitivity, responsivity and detectivity of 1.3×105, 1.07 mA/W and 5.25×1011 Jones at 0 V. Moreover, the response (0.34 s) and recovery time (0.28 s) of these devices were found to be smaller compared to those reported in literature.