Determination of the charge trap energy distribution in conjugated polymer MDMO-PPV

Abstract

The trap distribution depending on the exciting light spectral range and applied electrical field in the ,5-(3,77dimethyloctyloxy)] paraphenylenevinylene) was investigated by the thermally stimulated current (TSC) technique. To ensure selective excitation of the defect states we have used the long-pass colour filters with cut-on energies from 1.77 up to 3.10 eV. In order to evaluate the trap parameters of MDMO-PPV, curve fitting was done. The analysis revealed the Gaussian distribution of the defect states; the estimated effective activation energies were about 0.22 and 0.40 eV.

Gaussian Distribution of the Charge Traps in the Energy Gap of MDMO-PPV and Its Dependence on Synthesis Route Revealed by the Thermally Stimulated Current Spectroscopy

“…chain ends and irregularities of the polymer layer. Therefore, basing on these results the TSC curves were fitted by equation, which takes into account distribution of the trapping states in energy scale [23]: To limit the number of the fitting parameters, the initial density of the filled traps N t was determined according to Eq. (2) and the attempt to escape frequency v 0 was evaluated from the following relationship [24,25]:…”

Magnetoresistance in electrochemically deposited polybithiophene thin films

“…In semiconducting polymers, TSC is an efficient technique to access information about deep trap states present on a material [29][30][31][32][33]. It consists on the analysis of relaxation peaks of current dependent on temperature.…”

“…However, if their energies are not sufficiently separated, overlap of contribution due to each site can occur, resulting, for example, in a broader single peak curve [34]. As is known, the density of states on noncrystalline organic semiconductors can be well described by a Gaussian distribution of localized states due to its structural disorder and fluctuation in conjugation lengths, and this distribution also includes localized defects and trapping sites [32,35]. In this case, overlap can also occur, given rise to a more complex picture of energy trap distribution inside the material.…”