| Autor: |
Il Jake Choi J; Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.; Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141, Republic of Korea., Ono LK; Energy Materials and Surface Sciences Unit (EMSSU), Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan., Cho H; Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141, Republic of Korea., Kim KJ; Beamline Research Division, Pohang Accelerator Laboratory (PAL), Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea., Kang HB; Engineering Section, Okinawa Institute of Science and Technology Graduate University (OIST) 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan., Qi Y; Energy Materials and Surface Sciences Unit (EMSSU), Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa 904-0495, Japan., Park JY; Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.; Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141, Republic of Korea. |
| Abstrakt: |
While organic-inorganic hybrid perovskites are emerging as promising materials for next-generation photovoltaic applications, the origins and pathways of perovskite instability remain speculative. In particular, the degradation of perovskite surfaces by ambient water is a crucial subject for determining the long-term viability of perovskite-based solar cells. Here, we conducted surface characterization and atomic-scale analysis of the reaction mechanisms for methylammonium lead bromide (MA(CH 3 NH 3 )PbBr 3 ) single crystals using ambient-pressure atomic force microscopy (AP-AFM) and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) in environments ranging from ultrahigh vacuum to 0.01 mbar of water vapor. MAPbBr 3 single crystals, grown by a solution process, were mechanically cleaved under UHV conditions to obtain an atomically clean surface. Consecutive topography and friction force measurements in low-pressure water ( p water ≈ 10 -5 mbar) revealed the formation of degraded patches, one atomic layer deep, gradually increasing their coverage until the surface was entirely covered at a water exposure of 4.7 × 10 4 langmuir (L). At the perimeters of these degraded patches, a higher friction coefficient was observed, along with an interstitial step height, which we attribute to a structure equivalent to that of the MA-Br terminated surface. Combined with NAP-XPS analysis, our results demonstrate that water vapor induces the dissociation of surface methylammonium ligands, eventually resulting in the depletion of the surface MA and the full coverage of hydrocarbon species after exposure to 0.01 mbar of water vapor. |
