Absorption F-Sum Rule for the Exciton Binding Energy in Methylammonium Lead Halide Perovskites

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• 作者：Nicola Sestu ; Michele Cadelano ; Valerio Sarritzu ; Feipeng Chen ; Daniela Marongiu ; Roberto Piras ; Marina Mainas ; Francesco Quochi ; Michele Saba ; Andrea Mura ; Giovanni Bongiovanni
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2015
• 出版时间：November 19, 2015
• 年：2015
• 卷：6
• 期：22
• 页码：4566-4572
• 全文大小：394K
• ISSN：1948-7185

文摘

Advances of optoelectronic devices based on methylammonium lead halide perovskites depend on understanding the role of excitons, whether it is marginal as in inorganic semiconductors, or crucial, like in organics. However, a consensus on the exciton binding energy and its temperature dependence is still lacking, even for widely studied methylammonium lead iodide and bromide materials (MAPbI₃, MAPbBr₃). Here we determine the exciton binding energy based on an f-sum rule for integrated UV鈥搗is absorption spectra, circumventing the pitfalls of least-squares fitting procedures. In the temperature range 80鈥?00 K, we find that the exciton binding energy in MAPbBr₃ is E_B = (60 卤 3) meV, independent of temperature; for MAPbI₃, in the orthorhombic phase (below 140 K) E_B = (34 卤 3) meV, while in the tetragonal phase the binding energy softens to 29 meV at 170 K and stays constant up to 300 K. Implications of binding energy values on solar cell and LED workings are discussed.