Dimmable sunlight-like organic light emitting diodes with ultra-high color rendering index

• Novel dimmable sunlight-like white organic light-emitting diodes are presented.
• The spectra are like black body radiation with high color rendering index (CRI).
• Charge modification layers suppresses energy transfer between emitting materials.
• This study shows that covering a wide long-wavelength range is vital for high CRI.

We propose novel dimmable sunlight-like white organic light-emitting diodes that were fabricated using three luminophores to form an emitting spectrum similar to black body radiation at 2250 K with ultra-high color rendering index (CRI) value of 91, which nearly remained the constant at various luminance values ranging from 100 to more than 2500 cd/m2 at Commission Internationale de l’Eclairage chromaticity coordinates of (0.51, 0.41). Introducing charge modification layers suppressed the energy transfer between the emitting material layers and increased the probability of carrier recombination. Moreover, we reveal that covering long-wavelength ranges played a vital role in achieving high CRI values; the CRI values of a spectrum artificially shifted toward a long-wavelength direction (from 610 to 620 nm) remained constant, whereas those of a spectrum shifted toward a short-wavelength direction (from 610 to 600 nm) dropped to 79.