Japan Synchrotron Radiation Research Institute , 1-1-1 Kouto, 679-5198 Hyogo, Japan.
Institute of Physics SAS , Dubravska cesta 9, 84511 Bratislava, Slovakia.
ACS Appl Mater Interfaces. 2017 Mar 8;9(9):8241-8247. doi: 10.1021/acsami.6b15167. Epub 2017 Feb 27.
Solvent annealing is an efficient way of phase separation in polymer-fullerene blends to optimize bulk heterojunction morphology of active layer in polymer solar cells. To track the process in real time across all relevant stages of solvent evaporation, laboratory-based in situ small- and wide-angle X-ray scattering measurements were applied simultaneously to a model P3HT:PCBM blend dissolved in dichlorobenzene. The PCBM molecule agglomeration starts at ∼7 wt % concentration of solid content of the blend in solvent. Although PCBM agglomeration is slowed-down at ∼10 wt % of solid content, the rate constant of phase separation is not changed, suggesting agglomeration and reordering of P3HT molecular chains. Having the longest duration, this stage most affects BHJ morphology. Phase separation is accelerated rapidly at concentration of ∼25 wt %, having the same rate constant as the growth of P3HT crystals. P3HT crystallization is driving force for phase separation at final stages before a complete solvent evaporation, having no visible temporal overlap with PCBM agglomeration. For the first time, such a study was done in laboratory demonstrating potential of the latest generation table-top high-brilliance X-ray source as a viable alternative before more sophisticated X-ray scattering experiments at synchrotron facilities are performed.
溶剂退火是聚合物-富勒烯混合物中相分离的有效方法，可优化聚合物太阳能电池活性层的体异质结形态。为了实时跟踪溶剂蒸发所有相关阶段的过程，我们同时对模型 P3HT：PCBM 混合物在二氯苯中的溶解进行了基于实验室的原位小角和广角 X 射线散射测量。PCBM 分子团聚在混合物中固体含量约为 7wt%时开始。尽管在固体含量约为 10wt%时，PCBM 的团聚速度减慢，但相分离的速率常数没有变化，这表明 P3HT 分子链的聚集和重排。这个阶段持续时间最长，对 BHJ 形态的影响最大。在浓度约为 25wt%时，相分离迅速加速，其速率常数与 P3HT 晶体的生长相同。P3HT 结晶是最终阶段溶剂完全蒸发前相分离的驱动力，与 PCBM 团聚没有明显的时间重叠。这是首次在实验室中进行此类研究，展示了新一代台式高亮度 X 射线源的潜力，可作为在同步辐射设施进行更复杂的 X 射线散射实验之前的可行替代方案。
