Study of degradation in OLEDs by magneto-electroluminescence response

Device degradation of organic light emitting diodes (OLED) has been of continuing interest. Here we introduce a method of investigating OLED degradation via magneto-electroluminescent (MEL) response upon the application of relatively small magnetic field, B. The MEL in OLEDs requires spin-mixing among spin sublevels of e-polaron and h- polaron pairs, which may be provided by the difference of the g-values between the e-polaron and h-polaron, which is known as the “Δg mechanism”. At steady state the “Δg-mechanism” leads to a non-Lorentzian MEL(B) response when a broad distribution of spin lifetime and g-values exists. Using the MEL(B) response we have studied OLED degradation at various operation conditions such as prolonged illumination and exposure to atmosphere. The extracted spin lifetime distribution from the MEL response has been analyzed to gain deeper understanding of the device performance under these conditions.