Polymer Science and Technology Group, The School of Materials, The University of Manchester, Grosvenor Street, M1 7HS, UK.
J Colloid Interface Sci. 2010 Apr 15;344(2):261-71. doi: 10.1016/j.jcis.2009.12.062. Epub 2010 Jan 11.
Hybrid solar cells are third-generation solar cells that are colloidal in nature. The composites used as photoactive layers within hybrid solar cells comprise conjugated polymers and inorganic semiconductor nanoparticles (e.g., nanocrystals and nanorods). The composites are usually prepared by spin casting non-aqueous dispersions consisting of polymer, nanoparticles and a co-solvent blend. The factors governing colloidal stability of the dispersions used for composite preparation have not been reported in detail. Here, the factors governing the stability of non-aqueous ZnO nanocrystal and nanorod dispersions as well as the relationship between dispersion stability and the extents of nanoparticle aggregation within model composites are studied. The polymers used are poly[[(2-methyl-4-methoxyphenyl)imino]-9,9-di-(2'-ethylhexyl)-fluorene-2,7-diyl] (PTAA) and poly[2,6-(4,4-bis-(2-ethyhexyl)-4H-cyclopenta [2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzo thiadiazole)] (PCPDTBT). FTIR in conjunction with thermogravimetric analysis data showed that up to 30% of the surfaces for the as-prepared ZnO nanocrystals and nanorods were occupied by acetate ligands. 1-Propylamine was found to form covalent coordinate bonds with ZnO and this contributes the ability of this co-solvent to promote enhanced ZnO dispersion stability. The morphologies of the composites were investigated using optical microscopy, AFM and TEM. A strong link was found between colloidal stability of the parent ZnO dispersions, extent of nanoparticle aggregation within the composites and pK(a) for the conjugate acid of the co-solvent. Electrostatic interactions did not control ZnO dispersion stability or composite morphology. Extensive nanometer-scale nanoparticle aggregation was evident within the composites. This was attributed to incompatibility between the polymer and (ligand covered) ZnO nanoparticles. Strategies for reducing uncontrolled nanoparticle aggregation are suggested.
杂化太阳能电池是胶体性质的第三代太阳能电池。作为杂化太阳能电池中光活性层使用的复合材料包括共轭聚合物和无机半导体纳米粒子（例如纳米晶和纳米棒）。这些复合材料通常是通过旋涂由聚合物、纳米粒子和共溶剂混合物组成的非水分散体来制备的。用于制备复合材料的分散体的胶体稳定性的控制因素尚未详细报道。在这里，研究了非水 ZnO 纳米晶和纳米棒分散体稳定性的控制因素以及分散体稳定性与模型复合材料中纳米粒子聚集程度之间的关系。所使用的聚合物是聚[[(2-甲基-4-甲氧基苯基)亚氨基]-9,9-二-(2'-乙基己基)-芴-2,7-二基]（PTAA）和聚[2,6-(4,4-双-(2-乙基己基)-4H-环戊二烯[2,1-b;3,4-b']-二噻吩)-交替-4,7-(2,1,3-苯并噻二唑)]（PCPDTBT）。FTIR 结合热重分析数据表明，多达 30%的原始 ZnO 纳米晶和纳米棒表面被醋酸盐配体占据。发现 1-丙胺与 ZnO 形成共价配位键，这使得该共溶剂具有促进 ZnO 分散体稳定性增强的能力。使用光学显微镜、AFM 和 TEM 研究了复合材料的形态。发现原始 ZnO 分散体的胶体稳定性、复合材料中纳米粒子的聚集程度与共溶剂的共轭酸的 pK(a)之间存在很强的联系。静电相互作用不能控制 ZnO 分散体的稳定性或复合材料的形态。在复合材料中明显存在广泛的纳米级纳米粒子聚集。这归因于聚合物和（配体覆盖的）ZnO 纳米粒子之间的不兼容性。提出了减少不可控纳米粒子聚集的策略。
