with T a reference temperature. The denominator T0 is called the characteristic temperature. A high characteristic temperature implies a weak temperature dependence.
In order to check the consistency of Eq.(9) with the model as described by Eq.(3), the fitting parameters S1,S2,and S3 of LED R1 have been plotted for several junction temperature in Fig.6. These three parameters decrease exponentially with temperature. The slopes are more or less identical, suggesting that one common characteristic temperature can be identified. All single color diodes under test have proven to show the same behavior. Their corresponding characteristic temperature have been collected in Table II. Similar characteristic temperature have been reported in literature. However,the characteristic temperature depends on whether radiant or luminous flux is considered in Eq.(10)