Abstract: The factors influencing the current–voltage (I–V) characteristics of light-emitting diodes (LEDs) are investigated to reveal the connection of I–V characteristics under optical excitation and those under electrical excitation. By inspecting the I–V curves under optical and electrical excitation at identical injection current, it has been found that the I–V curves exhibit apparent differences in voltage values. Furthermore, the differences are found to originate from the junction temperatures in diverse excitation ways. Experimental results indicate that if the thermal effect of illuminating spot is depressed to an ignorable extent by using pulsed light, the junction temperature will hardly deflect from that under optical excitation, and then the I–V characteristics under two diverse excitation ways will be the same.

Key words: current–voltage characteristics, light-emitting diodes, optical excitation, electrical excitation, junction temperature