Thermal Stability and Cation Composition of Hybrid Organic–Inorganic Perovskites

Abstract

One of the great challenges of hybrid organic−inorganic perovskite photovoltaics is the material's stability at elevated temperatures. Over the past years, significant progress has been achieved in the field by compositional engineering of perovskite semiconductors, e.g., using multiple-cation perovskites. However, given the large variety of device architectures and nonstandardized measurement protocols, a conclusive comparison of the intrinsic thermal stability of different perovskite compositions is missing. In this work, we systematically investigate the role of cation composition on the thermal stability of perovskite thin films. The cations in focus of this study are methylammonium (MA), formamidinium (FA), cesium, and the most common mixtures thereof. We compare the thermal degradation of these perovskite thin films in terms of decomposition, optical losses, and optoelectronic changes when stressed at 85 °C for a prolonged time. Finally, we demonstrate the effect of thermal stress on perovskite thin films with respect to their performance in solar cells. We show that all investigated perovskite thin films show signs of degradation under thermal stress, though the decomposition is more pronounced in methylammonium-based perovskite thin films, whereas the stoichiometry in methylammonium-free formamidinium lead iodide (FAPbI 3 ) and formamidinium cesium lead iodide (FACsPbI 3 ) thin films is much more stable. We identify compositions of formamidinium and cesium to result in the most stable perovskite compositions with respect to thermal stress, demonstrating remarkable stability with no decline in power conversion efficiency when stressed at 85 °C for 1000 h. Thereby, our study contributes to the ongoing quest of identifying the most stable perovskite compositions for commercial application.

Structure, optoelectronic properties and thermal stability of the triple organic cation GAxFAxMA1−2xPbI3 system prepared by mechanochemical synthesis

“…This has been desired due to the association of this cation with the low stability of halide perovskites. 81,82 Perhaps, the system may offer a one-day rivalry as a more friendly, metal-less alternative to the current foremost CsFAMA triple cation halide perovskites as the frontrunners in solar cells. 83 We hope to conduct more studies elucidating the electrical, dielectric, and photovoltaic properties of this system and to explore more compositions, such as GA 2x FA x MA 1À3x PbI 3 and GA x FA 2x MA 1À3x PbI 3 .…”

Progress in the preparation and application of CsPbX3 perovskites

“…40 Moreover, Schwenzer et al investigated the effects of different cation compositions on the thermal stability of perovskite thin films; the surface material composition of FACsPbI 3 films was less affected than that of FAPbI 3 films after 500 h at 85 °C. 41 The poor thermal and moisture stability of organic–inorganic hybrid perovskite materials is caused by the facile phase transitions and the formation of hydrated phases near room temperature. 43 Kulbak et al explored the thermal stability of MAPbBr 3 and CsPbBr 3 by thermogravimetric analysis.…”

One-Step Blade Coating of Inverted Double-Cation Perovskite Solar Cells from a Green Precursor Solvent

“…28 However, in recent years, MAPbI3 perovskite absorber have been replaced by multi-cation perovskite precursor mixtures such as triple-cation formamidinium (FA)/methyl ammonium (MA)/cesium (Cs)-based perovskite compositions because of their higher resulting device efficiency and intrinsic structural stability. [29][30][31] By now, the research focus lies more on double-cation perovskite materials especially due to their thermal stability, which normally contain FA and/or Cs avoiding the highly volatile MA. 31,32 Unfortunately, producing a uniform and high-quality perovskite thin film from such more complex precursor solutions on large area via a scalable printing technique, such as blade coating, might be additionally challenging due to their intricate solution chemistry.…”

“…[29][30][31] By now, the research focus lies more on double-cation perovskite materials especially due to their thermal stability, which normally contain FA and/or Cs avoiding the highly volatile MA. 31,32 Unfortunately, producing a uniform and high-quality perovskite thin film from such more complex precursor solutions on large area via a scalable printing technique, such as blade coating, might be additionally challenging due to their intricate solution chemistry. 33,34 Thereby, next to the more technological vacuum-assisted perovskite conversion, [35][36][37][38] the quenching methods via heat and a gas stream are considered to be easily scalable.…”

“…Methylammonium lead triiodide (MAPbI 3 ) is the most widely used lead-halide perovskite material for PSCs as it is a defect tolerant semiconductor with extraordinary optoelectronic properties . However, in recent years, MAPbI 3 perovskite absorbers have been replaced by multi-cation perovskite precursor mixtures such as triple-cation formamidinium (FA)/methyl ammonium (MA)/cesium (Cs)-based perovskite compositions because of their higher resulting device efficiency and intrinsic structural stability. − By now, the research focus lies more on double-cation perovskite materials, especially due to their thermal stability, which normally contain FA and/or Cs, avoiding the highly volatile MA. , …”