Fig. 1. Details of top-emitting red OLEDs investigated. (a) Cross-section of OLEDs. (b) Microscope image of different sizes of OLEDs operated at 3 V. (c) Energy diagram. (a) CPL, capping layer; ETL, electron transport layer; HBL, hole blocking layer; EML, emission layer; EBL, electron blocking layer; HTL, hole transport layer; HIL, hole injection layer. (b) Each symbol indicates the types of electrodes: cathode (K) and anode (A).

Fig. 2. Current density–voltage–radiance characteristics of different OLEDs. We set the maximum current density during the measurements to prevent degradation caused by higher current densities. For the S-sized OLEDs, the maximum current density was limited to 160A/cm2, and for the L-sized OLEDs, it was limited to 180A/cm2.

Fig. 3. Frequency characteristics of OLEDs. (a) Frequency response measured at DC offset of 160A/cm2 for the S-size and 180A/cm2 for the L-size. (b) Comparison of EL bandwidth and PL bandwidth.

Fig. 4. Communication performance of OLEDs. (a) Summary of data rates at a BER of 5.54×10−3 for different types of OLEDs in a 2-m data link, with a DC offset current of 160A/cm2 for the S-size and 180A/cm2 for the L-size. (b) Data rates at a BER of 3.8×10−3 for our OLEDs, compared with single OLED results from the literature as a function of the link distance. Squares are drawn from the measured distance and the data rate to facilitate comparison of different results.