Improvement in light-extraction efficiency of light emitting diode using microlenses fabricated by a novel and cost-effective method

Abstract

A low cost, solution-based novel process was proposed, which avoids any photo-lithographically fabricated Si template and yet yields small dimension microlenses. The microlenses were fabricated using a well-known chemical technique called dewetting of polymer thin film. Polystyrene (PS) was used to make a polymer thin film with thickness ranging from 20 to 40 nm. Then, this PS film was kept in dewetting solution namely methylethylketone (MEK) to obtain the microlenses. Dimension of these microlenses was measured to be the order of 1–2 \({\upmu }\!\hbox {m}\). The effect of various microlens parameters such as diameter and area fraction on light-extraction efficiency was systematically studied. Improvement of 4% in extraction efficiency was obtained by employing it on white light emitting diode. The area fraction of microlenses was increased up to 0.34 by reducing the spin speed. The light-extraction efficiency was further enhanced up to 7% upon increasing the area fraction of microlenses.