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

作者：Sestu Nicola; Cadelano Michele; Sarritzu Valerio; Chen Feipeng; Marongiu Daniela; Piras Roberto; Mainas Marina; Quochi Francesco; Saba Michele; Mura Andrea; Bongiovanni Giovanni

来源：Journal of Physical Chemistry Letters, 2015, 6(22): 4566-4572.

DOI：10.1021/acs.jpclett.5b02099

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 (MAPbI(3), MAPbBr(3)). Here we determine the exciton binding energy based on an f-sum rule for integrated UV-vis absorption spectra, circumventing the pitfalls of least-squares fitting procedures. In the temperature range 80-300 K, we find that the exciton binding energy in MAPbBr(3) is E-B = (60 +/- 3) meV, independent of temperature; for MAPbI(3), in the orthorhombic phase (below 140 K) E-B = (34 +/- 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.

• 出版日期2015-11-19