Calculation of two-photon absorption by nanocrystals of CsPbBr3

Article

关键词: PEROVSKITE NANOCRYSTALS;    QUANTUM DOTS;    EMISSION;    CSPBX3;    ENHANCEMENT;    EXCITONS;    BR;   

DOI  :  10.1103/PhysRevB.103.045415

来源: SCIE

【 摘 要 】

We present calculations of the two-photon absorption cross section sigma((2))(omega) for nanocrystals (NCs) of the inorganic perovskite CsPbBr3 for photon energies omega ranging from the absorption threshold at 2 omega approximate to 2.3eV up to 2 omega = 3.1 eV. The calculations employ a 4 x 4 k.p envelope-function model, with final-state excitons described in a self-consistent Hartree-Fock approximation. The k.p corrections to sigma((2))(omega) are found to be rather large, giving a reduction of about 30% in the cross section at the largest energies considered. The cross section is shown to be independent of polarization in the effective-mass approximation (EMA), but including k.p corrections leads to a small difference in sigma((2))(omega) between circular and linear polarization, which rises to about 16% at 2 omega = 3.1 eV. The theoretical cross section follows closely a power-law dependence on NC size, sigma((2))(omega)proportional to L alpha, with theoretical exponents alpha = 3.4 (EMA) or alpha = 3.2 (4 x 4 k.p model), in excellent agreement with experiment. The dominant contribution to the exponent alpha is shown to be the number of final-state excitons per unit energy. Measured values of the absolute (normalized) cross section sigma((2))(omega) show a large spread of values, differing by as much as a factor of 25 for some NC sizes. Our calculations strongly favor a group of measurements at the lower end of the reported range of sigma((2))(omega).

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