Preparation of a Periodic Polystyrene Nanosphere Array Using the Dip-Drop Method with Post-deposition Etching and Its Application of Improving Light Extraction Efficiency of InGaN/GaN LEDs

In this study, we synthesized a periodic polystyrene nanosphere (PS NS) array using the dip-drop method with post-deposition etching to improve the light extraction efficiency (LEE) of InGaN/GaN light-emitting diodes (LEDs). The dip-drop method has advantages such as simple procedure, inexpensive equipment, room temperature deposition, and easy implementation in LEDs. The arrangement of PS NSs on an indium-tin-oxide (ITO)-coated glass substrate depends on the average dip-drop speed and the concentration of the PS NS suspension. The periodic PS NS array can modulate the in-plane wave vector of emission light from a semiconductor to free space and thus increase the escape probability. The calculated and experimental results indicated that the light output intensity of the InGaN/GaN LEDs can be improved by using the periodic PS NS array as a window layer; this array comprises PS NSs with a diameter of 100 nm separated with periods of 100 and 100 nm in the x and y directions. Because of the improved LEE, the InGaN/GaN LEDs with the optimal PS NS array window layers exhibited a 38% increase in light output intensity compared with the conventional InGaN/GaN LEDs under 20-mA driving current.