Colour calculations
Colour outputs in SunSolve Power quantify the perceived colour of the simulated device under a specified illumination spectrum based on the wavelength‑dependent reflectance and transmittance calculated by the optical solver. You can enable colour calculations on the Inputs → Options tab by selecting Enable colour solver, and the results are reported on the Outputs → Colour tab.
Colour calculations
Section titled “Colour calculations”Colour outputs are calculated from the upward hemispherical spectrum (front colour), the downwards hemispherical spectrum (rear colour), and, if a detector is included, the spectrum incident to the detector (detector colour).
The program effectively ‘averages’ the colour of the module components that reflect light. For example, if a module contains a dark blue cell surrounded by a white backsheet, its ‘averaged’ colour might appear light blue; and if the cell also had fingers, then the ‘averaged’ colour might be a bluey-grey.
XYZ is a device-independent representation of colour. It does not depend on the display monitor.
The precision of XYZ increases as the number of rays increases and as the wavelength interval decreases (down to 1 nm).
XYZ is scaled such that Y = luminosity. SunSolve does not determine the absolute luminosity of the colour; the luminosity is merely an input.
XYZ depends on the incident spectrum as well as the reflection, absorption, and transmission of the simulated structure.
XYZ will only be calculated if the inputs for the minimum and maximum wavelengths are ≤360 nm and ≥830 nm, respectively.
RGB, LAB and LUV are all calculated from XYZ. These outputs depend on the white point of the chromatic display type. Most computer monitors have an sRGB display type where the white point is based on the 6504 K spectrum. RGB also also depends on the chromaticity coordinates and gamma curves of the chromatic display type.
Not all XYZ can be represented as RGB. When this occurs, we take the approach described by Walker, where we determine the RGB to be the intercept between the line that joins the xy point to the white point and the nearest side of the sRGB triangle. An example is given by McIntosh (2018).
On the colour outputs tab, RGB is presented as values and as a block of colour. If your monitor’s display colour is not calibrated, the colour viewed for a particular RGB might be incorrect.
In summary, RGB can be a useful output but if you’re not very familiar with colour representation, treat it as an approximate ‘averaged’ colour of the structure.
McIntosh (2018) presents examples of determining the colour of a solar cell and module. It describes how the colour depends on the illumination source and the detector.