Investigations into the Opto-electronic Properties of Polymer Composites Oriented Through Either Self-Assembly or Inorganic Templating.

摘要

Conjugated polymers (CPs) are attractive as a replacement for silicon as the active material for many semiconductor based electronics. However, the performance of CP based devices is still much lower than their silicon counterparts. Photovoltaics based upon CPs have comparatively low conversion efficiencies, at least an order of magnitude less than inorganic systems. This is in large part do to the poor control of the nanoscale morphology within the commonly employed donor/acceptor blend films. Similarly, integrated circuit components using CPs, such as field effect transistors (FETs), suffer from low electronic carrier mobilites. In the case of CP FETs electronic carrier mobilities remain low due to the lack of control over the molecular confirmation and alignment of the polymer chains within CP thin films.;In the case of CP based photovoltaic systems we address this issue by using a combination of self-assembly, tailored chemical synthesis and material architecture engineering which allow us an unprecedented level of control over the nanoscale morphology of donor/acceptor thin films. Atomic force microscopy (AFM) and grazing incidence x-ray diffraction (GIXRD) show that each of these approaches control the morphology within the blend films. Under solar simulation, electronic measurements show that this morphological control yields a commensurate increase in device performances.;For polymer FET devices, a self-assembly approach was used to enhance carrier mobilities. In this case we have used surfactant templated mesoporous silica (MPS) as a host matrix for CP systems. Uniaxial alignment within the host matrix is transferred to the polymer molecules such that they are straightened and aligned. The optical anisotropy of the polymer molecules is measured by polarized absorption and fluorescence spectroscopy. FETs fabricated using the composite mesoporous silica:polymer system as the active material produce hole mobilities one order of magnitude larger than any previously reported values for CPs.