Low temperature transient response and electroluminescence characteristics of OLEDs based on Alq₃

Highlights: • The dependency relation between transmission rate and electron transport layer is revealed. • The critical temperature points for the influence of luminescent materials and injection barriers on delay time are found. • The influence of light-emitting material and injection layer on carrier accumulation is quantified. - Abstract: In this work, the organic light-emitting diodes (OLEDs) based on Alq₃ are fabricated. In order to make clear the transport mechanism of carriers in organic light-emitting devices at low temperature, detailed electroluminescence transient response and the current-voltage–luminescence (I–V–L) characteristics under different temperatures in those OLEDs are investigated. It founds that the acceleration of brightness increases with increasing temperature is maximum when the temperature is 200 K and it is mainly affected by the electron transport layer (Alq₃). The MoO₃ injection layer and the electroluminescent layer have great influence on the delay time when the temperature is 200 K. Once the temperature is greater than 250 K, the delay time is mainly affected by the MoO₃ injection layer. On the contrary, the fall time is mainly affected by the electroluminescent material. The V_f is the average growth rate of fall time when the temperature increases 1 K which represents the accumulation rate of carriers. The difference between V_f caused by the MoO₃ injection layer is 0.52 us/K and caused by the electroluminescent material Ir(ppy)₃ is 0.73 us/K.