Highly reflective porous films via polymerization-induced phase separation and application on phosphor-converted light-emitting diodes

We propose a highly reflective porous polymer film, fabricated by polymerization-induced phase separation (PIPS), to be integrated on the reflective cup of light-emitting diode (LED) lamps. In detail, a liquid mixture consisting of monomers of polymers, porogens and photoinitiator is used as the formulation of phase separation process. Different reflectivity is achieved by easily tuning the film thickness. With an optimized film thickness of ~55 μm, the porous polymer film features an average reflectivity of ~ 92.18% in the visible wavelength range 400-800 nm. When applied on the LED reflective cup, the porous films improve the optical efficiency of LED lamps and the angular color uniformity. The measurement results show that compared with the LED lamp without porous films, the luminous flux of the LED with porous films increases by 11.56% with the 60% weight percent of phosphor in phosphor- polydimethylsiloxane ( PDMS)layer at the current of 100 mA and the correlated color temperature deviation decreased from 34561 K to 2743 K with the 47.37% weight percent of phosphor in phosphor-PDMS layer at the current of 100 mA. Therefore, the porous polymer film made by polymerization-induced phase separation is a promising material to promote the optical performance of LED lamp.