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Heterogeneous Cationa??Lattice Interaction and Dynamics in Triple-Cation Perovskites Revealed by Infrared Vibrational Nanoscopy
摘要： Hybrid organic-inorganic perovskites exhibit extraordinary photovoltaic performance. This is believed to arise from almost liquid-like low-energy interactions among lattice ions and charge carriers. While spatial variations have recently been identified over multiple length scales in the optoelectronic responses, the relationship of the heterogeneity and the soft cation-lattice interactions has remained elusive. Here, we apply multivariate infrared vibrational nano-imaging to a formamidinium (FA)-methylammonium (MA)-cesium triple cation perovskite. By using the FA vibrational resonance as a probe of its local chemical environment, through spatial variation and correlation in composition, strength of cation-lattice coupling and its associated few-ps vibrational dynamics, we reveal how a varying local reaction field is correlated with the cation-lattice coupling. We attribute the associated heterogeneous lattice contraction to a non-uniform distribution of cesium cations. The observed varying elasticity of the lattice leads to disordered charge-phonon coupling and polaron formation, the control of which is central to improving perovskite photovoltaics.
关键词： charge-phonon coupling,infrared vibrational nano-imaging,Hybrid organic-inorganic perovskites,lattice contraction,photovoltaic performance,cation-lattice coupling,polaron formation,vibrational dynamics
更新于2025-09-19 17:13:59
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Unusual Bimodal Photovoltaic Performance of Perovskite Solar Cells at Real-World Operating Temperatures
摘要： A deep understanding of environmental effects on perovskite solar cell (PSC) performance is highly desirable for further progress towards large-scale deployment of this technology. We investigate the operation of PSCs in the temperature range (15?50 C) and report an unusual bimodal behavior in photovoltaic (PV) performance, with positive and negative temperature coefficients (TCs) below and above room temperature (RT), respectively. Furthermore, the performance metrics exhibit hysteresis, as their values depend on whether the measurements are made during the heating or cooling stages of the experiment. Conventional semiconductor solar cells, in contrast, exhibit a monotonic and non-hysteretic performance decline in this temperature range. The variations in power conversion efficiency primarily follow changes in open-circuit voltage and fill factor. Photoluminescence data suggest that the performance variations below RT are accompanied by a reduction in defect-related traps in the perovskite absorber and a drop in interfacial built-in potential at the perovskite/transport layer interface. The behavior above RT follows the conventional trend and can hence be explained by charge-phonon interactions. Our findings offer significant insight into the salient PV properties and photophysics of perovskite materials that define their performance in the real-world operating temperature range.
关键词： charge-phonon coupling,temperature-dependent hysteresis,Perovskite solar cells,Temperature coefficient
更新于2025-09-19 17:13:59