Application of 2D-MoO3 nano-flakes in organic light emitting diodes: effect of semiconductor to metal transition with irradiation†
Abstract
The current work demonstrates efficient utilization of 2D-MoO3 nano-flakes as a hole injection layer (HIL) in organic light emitting diodes (OLEDs). Nano-flakes are synthesized using an organic solvent-assisted grinding and sonication method of liquid exfoliation for MoO3, and 8–16 nm thick flakes are obtained. The effect of solar illumination on the hole injection properties of these nano-flakes is then studied by exposing the nano-flakes for 0, 15, 30, 45, 60 and 120 min and using them as HIL in green OLED. The device results are then compared with the OLED having bulk MoO3 as HIL. OLEDs with nano-flakes as the HIL have shown better performance than the OLED with bulk MoO3 as the HIL due to the better semiconducting properties in the nano-flake phase. The luminous intensity is increased by increasing the duration of irradiation and was found to be optimum in case of nano-flakes irradiated for 30 or 45 min and then started to decrease with the increase of duration of irradiation. The current density in the OLEDs with nano-flakes as the HIL shows a switching from high resistance to low resistance; however, the sequential pattern of switching voltage was missing with the duration of irradiation. The current density also decreased for nano-flakes with 60 and 120 min of irradiation. Transition from the semiconducting to metal nature of nano-flakes by solar irradiation is suggested to be the reason behind this decrease in current density and luminous intensity with a longer duration of illumination.
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