We present a broadband free space light communication system using high-speed organic light emitting diodes (OLEDs) as transmitters. Firstly, we report the design and bandwidth measurements of micro-OLEDs with active area of 40 × 40μm2. For this OLED, a cut-off frequency up to 459 MHz is observed. Secondly, by applying Direct Current Optical Orthogonal Frequency Division Multiplexing (DCO-OFDM) with adaptive bit and energy loading techniques, a data rate of 2.85 Gb/s is achieved. The increase of bandwidth and throughput reported in the current work are attributed to the improvements at the material, device and transmission levels. At the material level, a low work function Calcium cathode and ALD encapsulation of OLED is considered. At the device level, the active area is reduced in size and the OLEDs thickness is optimized. At the transmission level, parameters such as bias voltage, modulation amplitude and clipping have been fine-tuned to obtain high data rate.