Facile light exposure of zinc oxide via interfacial engineering for boosting responsivity and detectivity in organic photodetectors

Abstract

This study shows results contributing to the effective detectivity improvement of PM6:Y6-based inverted self-powered organic photodetectors (OPDs) through interfacial treatment of zinc oxide (ZnO), which is widely used as an electron transport layer. ZnO has excellent charge mobility but reacts with oxygen on the surface due to photocatalysis to decompose conjugated bonds in organic semiconductors, thereby deteriorating device stability. However, by adjusting the photoreactivity, the oxygen vacancies on the surface were filled through ZnO exposure treatment to confirm the effect of interfacial modification and work function control induction. The light exposure treatment was optimized for 15 minutes, and the surface of the light exposed ZnO layer showed a smooth morphology, which also reduced the roughness of the PM6:Y6 active layer, resulting in efficient charge transport and limited recombination. In addition, as the valence band of ZnO shifts deep through light exposure treatment at the interface with the active layer, the hole injection barrier is enhanced, effectively suppressing the dark current at the reverse voltage. Based on the suppressed dark current, the detectivity was improved by 3.9 times compared to that of the pristine device to 1.21 × 10¹⁴ Jones at 0 V, and an improved photoresponse speed of 0.88 μs was also observed. In particular, the modified interface and energy level control effectively suppressed the noise current of the OPD, and showed a high signal-to-noise ratio of 51.9 dB. As a result, the light exposure treatment of ZnO is optimized through a facile route based on the characteristics of ZnO, providing interpretation and results from a new perspective turning the disadvantages into advantages.