Abstract
Low light outcoupling efficiency restricts the wide application of organic light‐emitting diodes in solid state light market although the internal quantum efficiency of the device could reach near to 100%. In order to improve the output efficiency, different kinds of microlens array on the substrate emission surface were designed and simulated using light tracing method. Simulation results indicate that the microlens array on the substrate could efficiently improve the light output efficiency and an enhancement of 1.8 could be obtained with optimized microlens structure design. The microlens array with semicircle shape using polymer material was fabricated on glass substrate by a facile approach. Finally, the organic device with microlens array substrate was manufactured and the light output of the device with surface microlens structure could increase to 1.64 times comparing with the device without microlens.
Highlights
Due to high power efficiency, simple fabrication processes, and wide-color covering, organic light-emitting diodes (OLEDs) are the focus of attentions in applications of display and solid state lighting [1, 2]
A facile approach of fabricating microlens array on substrate is introduced to enhance the light outcoupling for organic devices using traditional photolithography method
Different kinds of microlens array are simulated with ray trace software and optimized microlens array model with an enhancement of 80% light output efficiency that is obtained from the simulation results
Summary
Due to high power efficiency, simple fabrication processes, and wide-color covering, organic light-emitting diodes (OLEDs) are the focus of attentions in applications of display and solid state lighting [1, 2]. Many different approaches had been done with the aim of optimizing the light outcoupling for OLEDs, including low-index grids [6, 7], periodic corrugated structure [8], Bragg mirrors [9, 10], buckling patterns [11], photonic crystals [12, 13], antireflection coatings [14], and monolayer of SiO2 microparticles [15] Those methods focused on changing the contact surface of glass substrate with organic device, which were complicated to achieve them. With respect to many previously reported studies on microlense fabrication method, here the easy achieved method using polymer photoresist is proposed, and by which ∼85% enhancement of the light extraction for OLED is obtained
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