Department of Chemistry, Northwestern University, 2220 Campus Drive, Evanston, Illinois 60208, USA.
ACS Nano. 2012 Mar 27;6(3):2032-40. doi: 10.1021/nn203328n. Epub 2012 Mar 7.
One of the challenges facing bulk heterojunction organic solar cells is obtaining organized films during the phase separation of intimately mixed donor and acceptor components. We report here on the use of hairpin-shaped sexithiophene molecules to generate by self-assembly grooved nanowires as the donor component in bulk heterojunction solar cells. Photovoltaic devices were fabricated via spin-casting to produce by solvent evaporation a percolating network of self-assembled nanowires and fullerene acceptors. Thermal annealing was found to increase power conversion efficiencies by promoting domain growth while still maintaining this percolating network of nanostructures. The benefits of self-assembly and grooved nanowires were examined by building devices from a soluble sexithiophene derivative that does not form one-dimensional structures. In these systems, excessive phase separation caused by thermal annealing leads to the formation of defects and lower device efficiencies. We propose that the unique hairpin shape of the self-assembling molecules allows the nanowires as they form to interact well with the fullerenes in receptor-ligand type configurations at the heterojunction of the two domains, thus enhancing device efficiencies by 23%.
在本体异质结有机太阳能电池中，面临的挑战之一是在供体和受体成分紧密混合的相分离过程中获得有序的薄膜。我们在此报告使用发夹状六噻吩分子作为供体成分，通过自组装生成具有凹槽的纳米线，以制备本体异质结太阳能电池。通过旋涂制备光伏器件，通过溶剂蒸发产生自组装纳米线和富勒烯受体的贯穿网络。发现热退火通过促进畴生长而提高功率转换效率，同时仍然保持这种纳米结构的贯穿网络。通过从不形成一维结构的可溶性六噻吩衍生物构建器件来检查自组装和凹槽纳米线的好处。在这些系统中，热退火引起的过度相分离导致缺陷的形成和器件效率的降低。我们提出，自组装分子的独特发夹形状允许纳米线在形成时与受体配体型构型中的富勒烯在两个畴的异质结处很好地相互作用，从而将器件效率提高 23%。
