Hole injection and electron overflow improvement in InGaN/GaN light-emitting diodes by a tapered AlGaN electron blocking layer.

A tapered AlGaN electron blocking layer with step-graded aluminum composition is analyzed in nitride-based blue light-emitting diode (LED) numerically and experimentally. The energy band diagrams, electrostatic fields, carrier concentration, electron current density profiles, and hole transmitting probability are investigated. The simulation results demonstrated that such tapered structure can effectively enhance the hole injection efficiency as well as the electron confinement.

High thermal stability of correlated color temperature using current compensation in hybrid warm white high-voltage LEDs.

This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Δu'v' values ranging from 0.

Improvement in uniformity of emission by ZrO₂ nano-particles for white LEDs.

The high luminous efficiency and superior uniformity of angular-dependent correlated color temperature (CCT) white light-emitting diodes have been investigated by ZrO₂ nano-particles in a remote phosphor structure. By adding ZrO₂ nano-particles with silicone onto the surface of the phosphor layer, the capability of light scattering could be enhanced. In particular, the intensity of blue light at large angles was increased and the CCT deviations could be reduced.

A novel randomly textured phosphor structure for highly efficient white light-emitting diodes.

We have successfully demonstrated the enhanced luminous flux and lumen efficiency in white light-emitting diodes by the randomly textured phosphor structure. The textured phosphor structure was fabricated by a simple imprinting technique, which does not need an expensive dry-etching machine or a complex patterned definition. The textured phosphor structure increases luminous flux by 5.

Patterned structure of remote phosphor for phosphor-converted white LEDs.

High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region.