Thermodynamic Limitation on the Conversion of Heat into Light

摘要: The problem of converting ambient heat into luminescence radiation is analyzed in terms the thermodynamics electromagnetic field. process described technical efficiency a light source η, defined as ratio power leaving form to supplied work. For at temperature T, it shown that limitation imposed by is, steady state, η≤1+T/(Tf−T), where Tf net rate which field carries energy away from entropy result emission. Thus, T/(Tf−T) maximum possible contribution source.An explicit expression for and spectral distribution emission obtained. It Tf≥T, monotonic increasing function integrated intensity bandwidth spectrum. moderate intensities finite (but narrow) bandwidths, approximately equal brightness source, concluded forbids efficiencies greater than about 160% room-temperature sources practical brightness. As an example, calculated (green) band typical ZnS phosphor.