Luminous Power Efficiency Optimization of a White Organic Light-emitting Diode by Tuning Its Spectrum and Its Extraction Efficiency

We show an increase of the luminous power efficiency of a white organic light-emitting diode (LED) with three emitters by optimizing its spectrum and its extraction efficiency. To calculate this efficiency we use a model with four parameters: the spectra, extraction efficiencies, internal quantum efficiencies of three emitters, and the driving voltage. This luminous power efficiency increases by 30% by use of a spectrum close to the spectrum of the MacAdam limit. This limit gives the highest luminous efficacy for a given chromaticity. We also show that a white organic LED with an inefficient deep blue emitter can give the same luminous power efficiency as a white organic LED with a more efficient light blue emitter, because of their different fractions in the radiant flux. Tuning the extraction efficiency with a microcavity to the spectrum also increases the luminous power efficiency by 10%.