An organic electroluminescent device ("OELD") has a controllable brightness, an improved energy efficiency, and stable optical output at low brightness. The OELD is activated with a series of voltage pulses, each of which has a maximum voltage value that corresponds to the maximum power efficiency when the OELD is activated. The frequency of the pulses, or the duty cycle, or both are chosen to provide the desired average brightness.
This invention was first conceived or reduced to practice in the performance of work under contract DE-FC26-00NT40989 awarded by the United States Department of Energy. The United States of America may have certain rights to this invention.