An effective method of predicting perovskite solar cell lifetime–Case study on planar CH₃NH₃PbI₃ and HC(NH₂)₂PbI₃ perovskite solar cells and hole transfer materials of spiro-OMeTAD and PTAA

As stability of perovskite solar cells remains a significant research topic, it is important to be able to predict the long-term stability of any new kinds of perovskite solar cells when new perovskite absorber materials or transport layers or new cell structures are being demonstrated. This work reports a reliable method of determining degradation rate which is resulted from thermal stress. By incorporating three kinds of accelerated tests, the activation energy for photo-thermally driven degradation processes of perovskites solar cells was determined, which is then used to predict its long-term stability using an Arrhenius equation. In addition, thermal stability of CH₃NH₃PbI₃, HC(NH₂)₂PbI₃, PTAA (poly[bis(4-phenyl)(2,4,6-trimethyl phenyl)amine]) and Spiro-OMeTAD (2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]−9,9'-spirobifluorene) are studied. The thermal stability of a planar HC(NH₂)₂PbI₃/PTAA device is better than a planar HC(NH₂)₂PbI₃/Spiro-OMeTAD device which in turn is better than a planar CH₃NH₃PbI₃/Spiro-OMeTAD device due to better thermal stability of HC(NH2)2PbI3 and PTAA. It is predicted that a planar HC(NH₂)₂PbI₃/PTAA device can have a lifetime of more than 3 years (or 1.5 years) at room temperature if 50% (or 25%) drop in power output can be tolerated. While these lifetimes are specific to perovskite material chosen, preparation method and solar cell design, the lifetime prediction method reported here can be verified experimentally. Therefore, the lifetime calculation method developed in this work is a quick and useful tool for determining the relative stability of a perovskite device especially when comparing the merits of different cell structure designs.