Performance of white light emitting diodes prepared by casting wavelength‐converting polymer on InGaN devices

ABSTRACT UV‐curable siloxane oligomers prepared by a hydrosilylation reaction were used as encapsulant. Two fluorescent copolymers with emission covering the range of green and red light were synthesized and blended with the UV‐curable siloxane oligomers and photoinitiator to make the wavelength‐converting polymer (WCP). WCP was casted on blue light emitting InGaN diodes and UV cured to fabricate white light emitting diodes (WLEDs). Effects of monomer compositions on the fluidity of uncured oligomer, together with the optical, thermal, and mechanical properties of the cured polysiloxane were studied. We also investigated the influence of red fluorescent polymer which was comprised of repeating units of dioctylfluorene, bisthienyl‐benzothiadiazole, and benzothiadiazole segments on the color rendering index, correlated color temperature, and luminous efficacy of WLED. Because of the good match between the absorption and emission features of the segments in the fluorescent copolymers, white LEDs can be produced by fluorescent copolymer blends which can support incomplete energy transfer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45210.