Disorder controlled hole transport in MEH-PPV

Abstract

We analyze the correlation between nanostructure and charge transport in poly(2-methoxy,5-(2'ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV) films. The MEH-PPV films prepared in toluene (TL) as well as chlorobenzene (CB) solvents were investigated using the time-of-flight method and x-ray scattering. Nondispersive hole transport was observed at room temperature in devices prepared from both solutions. The field and temperature-dependent mobility were analyzed by the Gaussian disorder transport model. The positional disorder parameter in CB is larger than that in TL films. Both energy and position disorders affect the transport property in the devices from CB whereas only energy disorder affects this property in devices from TL. Correspondingly, according to the x-ray scattering measurements, the TL-cast films have larger chain-packed domains and less order-disorder transition interfaces than those for CB-cast films, along the surface normal, i.e., the charge transport direction

Review of Morphology Dependent Charge Carrier Mobility in MEH‐PPV

“…2. 23 These results suggest that position disorder dominates the charge transport characteristics of MEH-PPV and energy disorder effects only become visible in samples having lower position disorders, i.e., for samples having large position disorder, positional disorder dominates charge transport characteristics and affects the change from non-dispersive transport to dispersive transport.…”

“…1 shows the hole transient of drop-cast MEH-PPV devices prepared from the solvents chlorobenzene and toluene. 23 The transients show non-dispersive behaviours which consist of an initial peak due to RC time constant at the beginning followed by a plateau and than a long declining edge indicating that the hole transport is non-dispersive (ND) for both films. While the transit time of faster arriving carriers can be seen in the linear scale for ND behaviour, the transit times were determined form the log i-log t plot.…”

“…Fig. 2 shows the temperature dependence of devices prepared from chlorobenzene and toluene from 225 K to 325 K at the interval of 10 K. 23 The electric field dependence of mobility follows Poole-Frenkel behaviour,…”

“…22 As these polymers tend to form a mixture of amorphous and crystalline structures, small angle X-ray diffraction (SAXS) is needed to provide information about mesoscale structures. 23 In this paper, we review the morphology (bulk and surface) dependent charge carrier mobility with respect to solvents (used for device fabrications), temperature (annealing), film fabrication process (spin cast, drop cast), and charge transport direction (parallel and perpendicular to the substrate).…”

A New Approach to the Synthesis of Nanocrystal Conjugated Polymer Composites

“…This relative imbalance limits the performance of any optoelectronic device based upon the material. Nanocrystals, by acting as a percolated high mobility pathway for electrons, offsets this imbalance [7]. It is thought that photoexcited charge separation occurs at the nanocrystal-polymer interface [8].…”