Hybrid polymer:inorganic-nanoparticle composite devices for photodetection and photovoltaics
Thapa, Ram B.
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Conjugated organic polymers and molecules exhibit semiconducting properties which are in many respects similar to those of traditional inorganic semiconductors that make them suitable for practical optoelectronic devices. Hybrid inorganic-organic nanocomposites are rapidly emerging as alternatives to traditional optoelectronic devices as they combine the properties of both inorganic and organic materials and they can be chosen to cover the entire spectral range from ultraviolet (UV) to infrared (IR). In addition, the performance of photo-responsive devices based on these hybrid materials can be improved by the incorporation of new additive components like pentacene, and single wall carbon nanotubes (SWNTs) that can help in charge transport. In this thesis, we present an infrared active thin film polymeric photovoltaic device fabricated from a nanocomposite of regioregular polymer P3HT, monodispersed quantum dots of PbSe and the organic semiconductor pentacene by using colloidal solution processing. The PbSe quantum dots serve as infrared photosensitizers due to their tailorable absorption characteristics at infrared wavelengths. The current voltage measurements of the device show that the photovoltaic performance is significantly increased by the introduction of pentacene. The improved performance of the device is attributed to the high mobility of charge carriers in pentacene. Specifically, the π-stacked ordered geometry of pentacene provides highly conducting domain in the device. In addition, we also present the enhancement of photodetection in a hybrid nanocomposite by the inclusion of SWNTs. The SWNTs were attached to PbSe QDs by a novel chemical method.