Optoelectronic Modelling, Circuit Design and Modulation for Polymer-Light Emitting Diodes for Visible Light Communication Systems

Abstract

This paper investigates the use of organic polymer light emitting diodes (PLEDs) for the use in visible light communications (VLC). We prepared blue and green emitting PLEDs using commercial light-emitting polymers, and then characterised the device emission (spectrum and power), and extracted their circuit parameters for their electrical equivalent model for driving with small signals. In addition, we characterised the bandwidth ($\boldsymbol{B_{mod}}$) of the devices over a period of continuous driving (∼ 4 h) and found that for the blue PLEDs the $\boldsymbol{B_{mod}}$ decreased from an initial 750 kHz to a steady state of ∼250 kHz. The green-emitting devices were found to benefit from an extended $\boldsymbol{B_{mod}}$ of ∼1.5 MHz at the beginning of the test, which then stabilised to ∼850 kHz. Furthermore, with the addition of a first order RC filter we show that, the steady state $\boldsymbol{B_{mod}}$ of the blue PLED cane be increased by a factor of ∼3, thus allowing > 1 Mbps non-return to zero on-off keying (NRZ OOK) data transmission in a complete VLC system.