摘要
有机太阳能电池中的金属电极/活性层界面对载流子传输和复合等过程产生重大的影响,最终影响器件的性能。因此,界面结构调控是制备高性能有机太阳能电池的关键。利用瞬态光伏(TPV)、载流子提取法(CE)和同步辐射光电子能谱(SRPES)研究了有机太阳能电池中Ca/Al电极界面性质与器件性能之间的内在联系。金属Ca插入层减弱了金属Al电极/PCDTBT界面处的电子注入势垒,从而有利于电子从PCDTBT传输到电极,并排斥空穴使其远离电极/活性层的界面,因此显著地降低电极/活性层界面处的载流子复合。此外,利用SRPES和近边X射线吸收精细结构谱(NEXAFS)研究了金属电极和聚合物间的界面相互作用,发现Ca与PCDTBT发生强烈的化学反应,导致PCDTBT分子结构发生破坏。因此,有必要在低功函金属电极和有机活性层间引入插入层(如LiF)来调控界面电子结构,同时阻止界面化学反应。这些信息为更好地理解金属/有机界面结构与器件性能的内在联系、研发高性能有机太阳能电池器件提供理论指导。
The interfaces between electrodes and active layers in organic photovoltaics(OPVs) have direct impact on the charge transport and extraction processes, ultimately influencing the device performance. The modification of interface would benefit the development of highly efficient OPV devices. In this study, transient photovoltage(TPV) and charge extraction(CE) measurements were used in combination with the synchrotron radiation photoemission spectroscopy(SRPES) to gain insight into the correlation between interfacial properties and device performance. Devices with a Ca interlayer exhibit a lower recombination as a result of the strong dipole moment produced by the Ca interlayer, which can facilitate the extraction of electrons and drive holes away from the cathode/polymer interface. In addition, Strong chemical reactions occur between Ca and PCDTBT, which destroy the molecular structure of PCDTBT. An insertion layer(Li F et al.) should be introduced between metal cathode and the active layer to prevent the reaction and tune the interfacial electronic structure.
引文
[1]Ju,H.X.;Knesting,K.M;Zhang,W.;Pan,X.;Wang,C.H.;Yang,Y.W.;Ginger,D.S.;Zhu,J.F.;ACS Appl.Mater.Interfaces 2016,8:2125