Fig. 2: Historical waterfall diagrams of energy loss channels in a generic mid/high-power white LED package.
a–d, Diagrams for 2003 (a), 2010 (b), 2016 (c) and 2020 (d). Losses are normalized to 1 Watt of electric power input. Represented energy loss channels, listed in each column in a, contribute to the following sub-efficiencies, listed below each column in d and defined in Supplementary Methods 3: ηVf, forward voltage efficiency; ηIQ, internal quantum efficiency; ηdroop, efficiency droop; ηLE, light extraction efficiency; ηC, light conversion efficiency; ηS, spectral efficiency; ηL, overall LED lamp efficiency. Numbers for each loss channel indicate energy losses both in relative terms of input power (in percentage) at the point of the channel and as absolute values (in Watts). Percentages for loss channels labelled by red, green and blue text indicate losses of corresponding remaining red/green/blue light energy. Note that absolute losses for individual loss channels may not always add up to the total loss due to the accumulation of rounding error. To the right of each waterfall diagram, the following representative LED architectures and light-source spectra used in calculations for each considered year are shown for reference: 2003, flip-chip with YGAG phosphor; 2010, flip-chip with 258 phosphor; 2016, flip-chip with PFS phosphor; 2020, chip-scale package flip-chip with SALON phosphor. On the spectral plots, the red curve shows the wavelength-dependent sensitivity of the human eye, whereas the black curve shows the spectrum of the light source. Details for each LED architecture are provided in Supplementary Note 2. Details on the phosphors for light down conversion are provided in Table 1 and Supplementary Note 5. Nonrad., non-radiative; scat., scattering. Source: own elaboration based on data on LED sub-efficiencies presented in Supplementary Note 3 and LED spectral data in Supplementary Note 5, with additional sources reported in Supplementary Note 6.
