Intensity Color

OLED emission color can change strongly with output angle: a device that appears yellow-green on-axis may shift toward cyan-green off-axis. Intensity Color converts the emission spectrum at each angle into chromaticity coordinates and color descriptors for evaluating that angular shift.

Example Setup

This page uses the top-emitting OLED case. Emission is detected through the semitransparent Ag top electrode. The Alq₃ emissive layer uses a broad synthetic spectrum with a peak near 530 nm and a red tail.

Structure direction: top medium → bottom medium

Optics enables only the Intensity detector in the Emission lane. The wavelength grid uses 1 nm, and three output angles make on-axis and off-axis emission directly comparable.

Generation Requirements

Intensity Color requires all of the following:

• Enable the Intensity detector.
• Set Wavelength Mode to Sweep.
• Set the wavelength range exactly to 360–780 nm.
• Use a wavelength step no greater than 5 nm.
• Enable Visible Color.

The 360–780 nm / ≤ 5 nm grid is a Dreapex TMM generation requirement, not a claim of physical-measurement conformity with ISO/CIE 11664-3:2019.

Set wavelength 360–780 nm, step 1 applies the detector, wavelength, and color settings in one action. Emission uses the emitter spectrum in the emissive layer; it neither requires nor reads the Propagation lane's Incident Spectrum.

Emission-Spectrum Convention

Each result row represents one output angle. Dreapex TMM first obtains intensity versus wavelength at that angle, then integrates it with the selected observer's color-matching functions to produce XYZ, xy, and the other color quantities. It is neither one color integrated over every output direction nor a physical measurement report.

The emitter's Spectrum Unit defines the input convention:

• Power is used directly as a relative radiant-power spectrum.
• Probability is converted to a power spectrum using photon energy before color calculation.

For one emitter, a common scaling from Conversion Efficiency or Multiplication Factor does not change chromaticity. With multiple emitters, their relative efficiencies and factors change the mixed spectrum and therefore the mixed color.

Chromaticity Diagram

The diagram draws one point for each angle with visible emission. In this example, the 0°, 30°, and 60° points move across the green region, directly showing angular color shift caused by the microcavity stack.

Connect Data Points joins the angle points to show the direction of color travel. All points share one brightness scaling, so their relative brightness can be compared. The swatches and sRGB values remain screen previews rather than absolute luminance or radiometric intensity.

Angles without visible emission are omitted and counted in a note below the result. The chart draws at most 2,000 points; when parameter combinations multiplied by angles exceed that limit, use the table and CSV.

Color Data Table

In a single run, table view shows one row per output angle. In a parameter Sweep, each row represents a parameter-combination-and-angle pair; a separate Angle column remains visible for multi-angle results. Columns controls only the on-screen view, while Export CSV always exports the complete result.

Color Metrics and Display

Baseline Row and Angular Color Shift

The table uses the first row as Baseline by default. Select another row with its radio button or the toolbar dropdown; Delta u′v′ immediately updates relative to the new baseline.

Delta u′v′ is the straight-line distance in the CIE 1976 u′v′ plane. CIE TN 001:2014 recommends it for describing angular chromaticity differences of light sources, but it defines no universal pass/fail threshold; apply the limit set by the display, lighting-product, or customer specification. For physical angle-resolved spectral and color measurement, refer to CIE 239:2020.

With 0° as the baseline, this example gives Delta u′v′ = 0.02569 at 30° and 0.06707 at 60°. Use these values together with the direction shown in the diagram instead of treating sRGB swatches as quantitative evidence.

Dominant Wavelength and Excitation Purity

Dominant wavelength describes the perceptual hue direction from equal-energy white E to the emission chromaticity point. It is not the spectral peak reported by Global Peak Wavelength:

• A plain number is the dominant wavelength on the spectral locus, in nanometres.
• A trailing c denotes the complementary wavelength for a purple-line color.
• When excitation purity pe < 0.01, chromaticity is too close to the achromatic reference for a stable hue direction, so wavelength is shown as —.

Dominant wavelength describes perceived hue; peak wavelength locates the maximum of the spectrum. They may be close for narrow, single-peak emission but should not be interchanged for broad, multi-peak, or strongly microcavity-shaped spectra.

CCT and Duv

CCT and Duv are available only with the 2° observer and use the Ohno (2014) method; see CIE TN 013:2022 for their scope:

• Duv > 0 places chromaticity above the Planckian locus and is typically greener near white; Duv < 0 places it below the locus and is typically pinker near white.
• CCT is shown only when |Duv| <= 0.05; outside that domain, CCT is — while Duv remains available.
• When 0.006 < |Duv| <= 0.05, CCT carries *. The ±0.006 reference band is a tool-chosen visual hint, not a binning or compliance verdict.

All three angles in this example have |Duv| > 0.05, so the table correctly keeps Duv and displays — for CCT. Highly saturated green emission lies far from the Planckian locus and cannot be described meaningfully by one correlated color temperature.

Observer and Sampling

The observer is frozen at run time. Rerun after switching between 2° and 10°:

• 2° uses the CIE 1931 diagram and provides CCT / Duv.
• 10° uses the CIE 1964 locus and hides gamut triangles, preset white points, and CCT / Duv.

Wavelength step may be <= 5 nm, but use 1 nm for color comparison. When the actual result grid is coarser than 1 nm, the page shows a nonblocking coarse-sampling note. Narrow emission peaks, especially those with FWHM below about 10 nm, are more sensitive to grid placement; the UI warning gives a possible shift on the order of Delta u′v′ = 0.005.

Next

Compare dominant wavelength with the spectral peak in Intensity Spectrum Peaks and Envelope FWHM, then use Mode to relate angular color shift to outcoupling and loss channels.