Nanostructured donor/acceptor interfaces in photovoltaic cells using columnar-grain films of a cross-linked poly(fluorene-alt-bithiophene)
作者:Joana Farinhas、Quirina Ferreira、Roberto E. Di Paolo、Luís Alcácer、Jorge Morgado、Ana Charas
DOI:10.1039/c1jm10195a
日期:——
We report on the fabrication of photovoltaic cells, PVs, with controlled donor/acceptor interfaces using a process based on the phase separation between a cross-linkable polyfluorene and polystyrene. Robust, nanostructured columnar-grain layers of a conjugated cross-linked polymer, F8T2Ox1 (an oxetane-functionalized derivative of poly(9,9-dioctylfluorene-alt-bithiophene)) are obtained after removal of polystyrene. These layers are used, in combination with 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61 (PCBM) deposited by spin coating, to define donor/acceptor interfaces, as PVs' active layers. The performance of these cells is dependent on the dimensions of the surface structures. In particular, a significant power conversion efficiency improvement is observed upon decrease of column diameter, reflecting an improvement of the exciton dissociation. We find, however, that these efficiencies still fall below those of the PVs based on blends of the same components, but are larger than the ones found for planar bilayer PVs. Furthermore, PVs based on blends of cross-linked F8T2Ox1 and PCBM showed enhanced efficiency and thermal stability with respect to PVs based on blends of PCBM and the non-cross-linkable analogue poly(9,9-dioctylfluorene-alt-bithiophene). Taking into account that the columnar-grain morphology is recognised as the “ideal” architecture for PVs' active layer provided the column radii are of the order of few nanometres, this work gives a new insight into how to achieve efficient organic photovoltaic cells through the use of cross-linkable conjugated polymers as the electron-donor component.
我们报告了一种基于交联聚氟烯和聚苯乙烯之间相分离的工艺,制造出具有可控供体/受体界面的光伏电池(PV)。去除聚苯乙烯后,获得了强韧的纳米结构柱状晶粒层,这是一种交联共轭聚合物F8T2Ox1(聚(9,9-二辛基氟烯-与-二噁烯)的一个氧杂环功能化衍生物)。这些层与通过旋涂沉积的1-(3-甲氧基碳酰基)丙基-1-苯基-(6,6)C61 (PCBM)结合,用于定义作为PV活性层的供体/受体界面。这些电池的性能依赖于表面结构的尺寸。特别地,随着柱直径的减小,观察到显著的功率转换效率提高,这反映了激子解离的改善。然而,我们发现这些效率仍低于基于相同组分混合物的PV,但高于平面双层PV的效率。此外,基于交联F8T2Ox1和PCBM混合物的PV在效率和热稳定性方面相较于基于PCBM和不可交联的类似物聚(9,9-二辛基氟烯-与-二噁烯)混合物的PV显示出增强的性能。考虑到柱状晶粒形态被认为是PV活性层的“理想”架构,只要柱半径在几个纳米的量级,本研究为如何通过使用可交联的共轭聚合物作为电子供体组件来实现高效有机光伏电池提供了新视角。