Besleaga Cristina, Abramiuc Laura Elena, Stancu Viorica, Tomulescu Andrei Gabriel, Sima Marian, Trinca Liliana, Plugaru Neculai, Pintilie Lucian, Nemnes George Alexandru, Iliescu Mihaiela, Svavarsson Halldor Gudfinnur, Manolescu Andrei, Pintilie Ioana
National Institute of Materials Physics , 077125 Magurele, Ilfov, Romania.
University of Bucharest , Faculty of Physics, Materials and Devices for Electronics and Optoelectronics Research Center, 077125 Magurele, Ilfov, Romania.
J Phys Chem Lett. 2016 Dec 15;7(24):5168-5175. doi: 10.1021/acs.jpclett.6b02375. Epub 2016 Dec 2.
We monitored the evolution in time of pinhole-free structures based on FTO/TiO/CHNHPbICl layers, with and without spiro-OMeTAD and counter electrodes (Ag, Mo/Ag, and Au), aged at 24 °C in a dark nitrogen atmosphere. In the absence of electrodes, no degradation occurs. While devices with Au show only a 10% drop in power conversion efficiency, remaining stable after a further overheating at 70 °C, >90% is lost when using Ag, with the process being slower for Mo/Ag. We demonstrate that iodine is dislocated by the electric field between the electrodes, and this is an intrinsic cause for electromigration of I from the perovskite until it reaches the anode. The iodine exhaustion in the perovskite layer is produced when using Ag electrodes, and AgI is formed. We hypothesize that in the presence of Au the iodine migration is limited due to the buildup of I negative space charge accumulated at the perovskite-OMeTAD interface.
我们监测了基于FTO/TiO/CHNHPbICl层的无针孔结构在有无螺环-OMeTAD和对电极（Ag、Mo/Ag和Au）情况下，于24°C黑暗氮气气氛中老化时随时间的演变情况。在没有电极的情况下，不会发生降解。虽然含Au的器件功率转换效率仅下降10%，在70°C进一步过热后仍保持稳定，但使用Ag时功率转换效率损失超过90%，而对于Mo/Ag来说，这一过程较慢。我们证明碘会因电极之间的电场而发生位错，这是I从钙钛矿中发生电迁移直至到达阳极的内在原因。使用Ag电极时，钙钛矿层中会出现碘耗尽现象，并形成AgI。我们推测，在有Au存在的情况下，由于在钙钛矿-OMeTAD界面处积累的I负空间电荷，碘的迁移受到限制。
