Phosphorous and Boron Doped Colloidal Silicon Nanocrystals in Conjugated Co-polymers
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1102-LL01-08
Phosphorous and Boron Doped Colloidal Silicon Nanocrystals in Conjugated Co-polymers Vladimir Svrcek, Hiroyuki Fujiwara, and Michio Kondo Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, 305-8568, Japan ABSTRACT One-way to improve organic solar cell efficiency is blending conjugated polymer with a second nanocomposite. We report on blending of freestanding boron- and phosphorous-doped environmental friendly silicon nanocrystals (Si-ncs) with two conjugated polymers i.e. (poly(3hexylthiophene) (P3HT) and poly[methoxy-ethylexyloxy-phenylenevinilene] (MEH PPV)). The electrochemical etching and pulverization of doped porous silicon films are used for fabrication of photesensitive Si-ncs/polymers blends. Processing of Si-ncs dispersed in polymers allows simple tuning of the Si-ncs concentrations in the blends. The blends with high Si-ncs concentrations are prepared and opto-electric properties are compared and discussed. Both types of polymers containing doped Si-ncs showed a photoconductivity response under illumination AM1.5 at ambient temperature and atmosphere.
INTRODUCTION Composites polymer based solar cells presents potential for renewable energy sources because they can be fabricated on large areas with low cost. The observation of ultrafast photoinduced charge transfer from a conjugated polymer to buckminsterfullerene has attracted wide scientific interest in photovoltaic community [1]. Nowadays the best performing organic solar cells based on a conjugated polymer are blended intimately with a second component, usually a fullerene, to achieve a ‘bulk heterojunction’ structure. It has been shown that the resulting large interfacial area leads to an increase in external quantum efficiency compared with devices fabricated with the polymer-layered structure [2, 3]. Silicon is mostly used in current photovoltaic technologies. The usefulness of silicon can be amplified in a form of tiny soluble nanocrystals with sizes less than quantum confinement limit. That nano-scale silicon can be a favorable material as a host composite in conjugated polymer [4]. Processing of Si-ncs in polymer in liquid phase allows the control of blend properties [4, 5]. Recently, observed minority carrier multiplication discovered in colloidally dispersed silicon nanocrystals (Si-ncs) [6] in principle recognizes the Si-ncs as one of the key materials for the development of next generation Si-ncs solar cells. Furthermore, Sincs also possess non-toxicity for the environment, and their simple integration in nowadays wellestablished silicon based photovoltaic technologies might bring considerable benefit for the hybrid organic/inorganic solar cell development. In the following we demonstrate that phosphorus and boron doped freestanding Si-ncs prepared by electrochemical etching can be used for fabrication of the photosensitive conjugated polymers based blends. Freestanding doped-Si-ncs are blended with two conjugated polymers i.e. (poly(3he
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