Capacitance and impedance spectroscopy studies of polymer light emitting diodes based on MEH-PPV:BT blends

•Effect of blending MEH-PPV and BT on the electronic properties of the PLEDs has been investigated using Capacitance and Impedance Spectroscopy (IS) techniques.•Minimum parallel resistance (Rp) is obtained for PLEDs with MEH-PPV:BT blend ratio of 1:3.•Absence of negative capacitance in MEH-PPV:BT blend devices shows the suppression of trap-assisted non-radiative recombination.•Maximum conductance at small bias voltages is obtained for PLEDs with MEH-PPV:BT blend ratio of 1:3.•Blend of MEH-PPV:BT (1:3 ratio) is a good material combination for single layer PLEDs with enhanced charge transport. Light emitting polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is blended with a wide bandgap electron transport material benzothiadiazole (BT) and its effect on the electronic properties has been studied by capacitance and impedance spectroscopy (IS) in PLEDs. The impedance data is fitted using equivalent circuit models and the minimum parallel resistance (Rp) at zero bias have been obtained for 1:3 ratio of MEH-PPV:BT blended devices. The negative capacitance (NC) shows the occurrence of the trap-assisted non-radiative recombination mechanism at low frequencies in the unblended MEH-PPV PLEDs. Further, this behavior is seen to be reduced in PLEDs with MEH-PPV:BT blends. This clearly suggests that the blending of MEH-PPV and BT at different weight ratios results in the suppression of trap-assisted recombination. This can be attributed to the elimination of trap states due to the dilution of semiconductor material on account of the addition of wide bandgap host material. Moreover, the blended devices have shown a significant improvement in the conductivity at small bias voltages.