In-Situ Measurement of Junction Temperature and Light Intensity of Light Emitting Diodes With an Internal Sensor Unit

This study designed and tested an innovative light-emitting diode (LED) chip with a built-in sensor. Two electrically isolated units, the LED (for light emission) and the sensor (for monitoring junction temperature and light intensity), were integrated on a single chip. The sensor unit determines the junction temperature by measuring the forward voltage; the light output power of the LED unit can be precisely extrapolated with a polynomial function based on the photocurrent and junction temperature. This novel structure enables the in-situ real-time monitoring of the LED junction temperature and light output power, which allows a highly detailed and/or in-field LED reliability analysis and provides valuable feedback information for smart LED lighting systems.