Rationalizing Phase Transitions with Thermal Annealing Temperatures for P3HT:PCBM Organic Photovoltaic Devices
Rationalizing Phase Transitions with Thermal Annealing Temperatures for P3HT:PCBM Organic Photovoltaic Devices
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DOI：
10.1021/ma202063k
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发表时间：
2012-02-14
期刊：
影响因子：
5.5
通讯作者：
Donald, Athene M.
中科院分区：
文献类型：
--
作者：
Pearson, Andrew J.;Wang, Tao;Donald, Athene M.
我们已经研究了一系列的有机光伏器件（OPV）的基础上的薄膜共混物的P3HT和PCBM和显示，通过比较设备的研究与表征的共混物的热转变，我们可以提供一个机械描述的最佳退火温度，以提高设备的运行效率。对于铸态P3HT：PCBM共混物薄膜，我们证明了两个玻璃化转变温度对应于两个组成不同的无定形状态的存在，这是迄今未报道的观察。我们证明，只有当薄膜被加热到高于共混物的上表观玻璃化转变温度时，器件效率才会得到改善。如果在最佳温度以上进行退火，则过度的相分离和膜光密度的部分降低导致器件效率的总体降低。这两个特征温度都取决于共混物的组成。因此，这些工艺之间的温度依赖性竞争打开了一个“窗口”，在该窗口内可以优化器件效率，并为未来的聚合物：富勒烯共混物OPV设计有效的退火方案提供了机会。
We have studied a range of organic photovoltaic devices (OPVs) based on a thin-film blend of P3HT and PCBM and show that, by comparing device studies with a characterization of the thermal transitions of the blend, we can provide a mechanistic description of the optimum annealing temperatures necessary to improve the operational efficiency of a device. For as-cast P3HT:PCBM blend thin-films we evidence two glass transition temperatures corresponding to the existence of two compositionally different amorphous states; an observation that is unreported to date. We demonstrate that an improvement in device efficiency only occurs once the film has been heated above the upper apparent glass transition temperature of the blend. If annealing is performed above the optimum temperature, excessive phase-separation and a partial reduction in film optical density leads to a general decrease in device efficiency. Both of these characteristic temperatures are dependent upon the composition of the blend. The temperature-dependent competition between such processes therefore opens a "window" within which device efficiency can be optimized and provides an opportunity to design effective annealing protocols for future polymer:fullerene blend OPVs.