The invention relates to a method for determining the maximum open circuit voltage and the power that can be output by a photoconverter material subject to a measurement light intensity, the method including the following steps: measuring the photoluminescent intensity of the material, measuring the absorption rate of the photoconverter material at a second wavelength substantially equal to the photoluminescent wavelength of the photoconverter material, determining the maximum open circuit voltage of the photoconverter material with the measurement light intensity by means of the absorption rate and the photoluminescent intensity measured at substantially the same wavelength; said invention being characterized in that the light source and the photoconverter material are arranged such that the angular distributions of the rays incident on and emitted by the lit surface of the material and collected by the detector are substantially identical.