title: Effect of Selective Contacts on the Thermal Stability of Perovskite Solar Cells.
abstract: Thermal stability of CH3NH3PbI3(MAPbI3)-based perovskite solar cells was investigated for normal structure including the mesoporous TiO2layer and spiro-MeOTAD and the inverted structure with PCBM and NiO. MAPbI3was found to be intrinsically stable from 85 °C to 120 °C in the absence of moisture. However, fast degradation was observed for the encapsulated device including spiro-MeOTAD upon thermal stress at 85 °C. Photoluminescence (PL) intensity and the time constant for charge separation increased with thermal exposure time, which is indicative of inhibition of charge separation from MAPbI3into spiro-MeOTAD. A full recovery of photovoltaic performance was observed for the 85 °C-aged device after renewal with fresh spiro-MeOTAD, which clearly indicates that thermal instability of the normal structured device is mainly due to spiro-MeOTAD, and MAPbI3is proved to be thermally stable. Spiro-MeOTAD with additives was crystallized at 85 °C due to a low glass transition temperature, and hole mobility was significantly deteriorated, which was responsible for the thermal instability. Thermal stability was significantly improved for the inverted structure with the NiO hole transporting layer, where the power conversion efficiency (PCE) was maintained at 74% of its initial PCE of 14.71% after the 80th thermal cycle (one cycle: heating at 85 °C for 2 h and cooling at 25 °C for 2 h). This work implies that the thermal stability of perovskite solar cells depends on selective contacts.
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Xing
authors.initials: X
authors.lastname: Zhao
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University , Suwon 440-746, Korea.|Laboratory of Photomolecular Science, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne, Switzerland.
authors.forename: Hui-Seon
authors.initials: HS
authors.lastname: Kim
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Ja-Young
authors.initials: JY
authors.lastname: Seo
authors.affiliation: School of Chemical Engineering, Sungkyunkwan University , Suwon 440-746, Korea.
authors.forename: Nam-Gyu
authors.identifier: http://orcid.org/0000-0003-2368-6300
authors.initials: NG
authors.lastname: Park
keywords: glass transition temperature; perovskite; selective contacts; solar cell; thermal-stability