Prevention of short circuits in solution-processed OLED devices

Pinholes in the emitting layer of an organic light emitting diode (OLED), e.g. induced by particle contamination or processing flaws, lead to direct contact between the hole-injection layer (HIL) and the cathode. The resulting short circuits give rise to catastrophic device failure. We demonstrate that these short circuits can be effectively prevented by an oxidative treatment of the HIL with aqueous sodium hypochlorite (NaClO(aq), bleach), which locally lowers the conductivity of the HIL (i.e. poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)) by more than eight orders of magnitude while leaving the emitting layer virtually unaffected. The oxidizer treatment is evidenced by an order of magnitude reduction in leakage current and strong reduction in the number of bright spots in the emitting area, without affecting the device lifetime. Diode behavior is even recovered in deliberately flawed devices containing 80 μm sized defects. © 2014 Elsevier B.V. All rights reserved.