title: Absorption F-sum rule for the exciton binding energy in methylammonium lead halide perovskites.
abstract: 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-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 MAPbBr3 is EB = (60 ± 3) meV, independent of temperature; for MAPbI3, in the orthorhombic phase (below 140 K) EB = (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.
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Sestu
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Cadelano
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Sarritzu
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Feipeng
authors.initials: F
authors.lastname: Chen
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Marongiu
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Piras
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Mainas
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Quochi
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Saba
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mura
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Cagliari , I-09042 Monserrato, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bongiovanni
keywords: UV−vis absorption; exciton binding energy; methylammonium lead halide perovskites; optical constants; optical properties