Self‐Assembled Nanowrinkle‐Network‐Structured Transparent Conductive Zinc Oxide for High‐Efficiency Inorganic Light‐Emitting Diodes

Abstract A ZnO nanowrinkle network (NWN) film is applied as a transparent conductive electrode (TCE) to improve the light extraction efficiency of inorganic light‐emitting diodes (LEDs). The NWN structures in sol–gel‐derived ZnO films are spontaneously formed by the evaporation of the solvent during prebaking to achieve the gelation of the sol–gel ZnO film. Despite the NWN structure, the optical transmittance of the NWN‐ZnO film prebaked at 130 °C is maintained at ≈92% with respect to that of unmodified glass. However, the optical transmittance of the NWN‐ZnO film prebaked at 150 °C is significantly decreased because of the increase in nanowrinkle density. As a result, the electroluminescence intensity of LEDs having the NWN‐ZnO TCEs increases significantly for the samples prebaked at temperatures up to 130 °C but decreases slightly in those treated at 150 °C. In addition, LEDs having the NWN‐ZnO film show enhanced spectral distribution over wide angles, which is important for lighting applications. On the basis of these results, the spontaneously assembled NWN‐ZnO films formed by the sol–gel method show potential for the low‐cost production of inorganic LEDs having high light extraction efficiencies.