Femtosecond two-photon absorption spectroscopy of copper indium sulfide quantum dots: A structure-optical properties relationship

Author(s)

dos Reis, George B. ^[1] ; Rodriguez, Ruben D. F. ^{[2, 3]} ; dos Santos, Calink I. L. ^[4] ; Gontijo, Leiriana A. P. ^[4] ; Schiavon, Marco A. ^[4] ; De Boni, Leonardo ^[2] ; Mendonca, Cleber R. ^[2] ; Vivas, Marcelo G. ^[1]

Affiliation

^[1] Univ Fed Alfenas, Lab Espect Opt & Foton, Pocos De Caldas, MG - Brazil

^[2] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

^[3] Univ Costa, Dept Ciencias Nat & Exactas, Barranquilla 080002 - Colombia

^[4] Univ Fed Sao Joao del Rei, Dept Ciencias Nat, Sao Joao Del Rei, MG - Brazil

• Document type: Journal article
• Source: Optical Materials; v. 86, p. 455-459, DEC 2018.
• Web of Science Citations: 1

Abstract

We have interpreted the two-photon absorption spectrum of water-soluble copper indium sulfide (CIS) QDs with stoichiometry 0.18 (Cu), 0.42 (In), and 2 (S) and an average diameter of approximately 2.6 nm. For that, we employed the wavelength-tunable femtosecond Z-scan technique and the parabolic effective-mass approximation model, in which the excitonic transition energies were phenomenologically corrected due to the stoichiometry of the nanocrystal. This model considers a conduction band and three valence sub-bands allowing excitonic transitions via centrosymmetric (Delta l = +/- 1, where l is the angular momentum of the absorbing state) and non-centrosymmetric (Delta l= 0) channels. In such case, this became relevant because the CIS QDs with chalco- pyrite crystalline structure is a non-centrosymmetric semiconductor. Thus, our experimental results pointed out two 2 PA allowed bands located at 715 nm (2hv = 3.47 eV) and 625 run (2hv = 3.97 eV) with cross sections of (6.3 +/- 1.0) x 10(2) GM and (4.5 +/- 0.7) x 10(2) GM, respectively. According to the theoretical model, these 2 PA bands can be ascribed to the 1P(1/2) (h(3))-> 1S(3/2) (e) (lower energy band) and 1P(1/2) (h(heavy)) -> 1S(3)(/2) (e) (90%)/(10%) 1P(1/2)(h(split-off)) -> 1P(3/2) (e) (higher energy band) excitonic transitions. A good agreement (magnitude and spectral position) between the experimental and theoretical data were obtained. However, our experimental data suggest that the higher-energy 2 PA band may have other contributions due to the mixing between the heavy-and the light-hole bands, which the effective mass model does not take into consideration. (AU)

• FAPESP's process: 15/20032-0 - Study on Nonlinear and Charge Transport Properties of Multi-branched Molecules via Quantum Chemical Methods.
• Grantee: Daniel Luiz da Silva
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/20886-1 - Ultrafast nonlinear optical spectroscopy: Transient Absorption and optical Kerr Gate with polarization control
• Grantee: Leonardo de Boni
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/12399-0 - Femtosecond pulses applied to nonlinear optics: spectroscopy, pulse shaping and microfabrication
• Grantee: Cleber Renato Mendonça
• Support Opportunities: Research Projects - Thematic Grants