Optical Absorption and Visible Photoluminescence from Thin Films of Silicon Phthalocyanine Derivatives

Abstract

The interest of microelectronics industry in new organic compounds for the manufacture of luminescent devices has increased substantially in the last decade. In this paper, we carried out a study of the usage feasibility of three organic bidentate ligands (2,6-dihydroxyanthraquinone, anthraflavic acid and potassium derivative salt of anthraflavic acid) for the synthesis of an organic semiconductor based in silicon phthalocyanines (SiPcs). We report the visible photoluminescence (PL) at room temperature obtained from thermal-evaporated thin films of these new materials. The surface morphology of these films was analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM indicated that the thermal evaporation technique is an excellent resource in order to obtain low thin film roughness when depositing these kinds of compounds. Fourier transform infrared spectroscopy (FTIR) spectroscopy was employed to investigate possible changes in the intra-molecular bonds and to identify any evidence of crystallinity in the powder compounds and in the thin films after their deposition. FTIR showed that there was not any important change in the samples after the thermal deposition. The absorption coefficient (α) in the absorption region reveals non-direct transitions. Furthermore, the PL of all the investigated samples were observed with the naked eye in a bright background and also measured by a spectrofluorometer. The normalized PL spectra showed a Stokes shift ≈ 0.6 eV in two of our three samples, and no PL emission in the last one. Those results indicate that the Vis PL comes from a recombination of charge carriers between conduction band and valence band preceded by a non-radiative relaxation in the conduction band tails.

Preparation of Hybrid Materials Containing M(II)Pc (M = Fe, Co, Ni)/Nylon films with Optical and Electrical Properties

“…The optical band gap was determined from the analysis of the spectral dependence of the absorption near the fundamental absorption edges. Evaluation of the absorption coefficient α is defined by the Lambert-Beer law and can be calculated from the optical transmittance [20] [21]. The absorption coefficient α in many amorphous semiconductors shows an exponential dependence on photon energy usually obeying the empirical relation [21]- [23]:…”

Revealing the Chemistry between Band Gap and Binding Energy for Lead‐/Tin‐Based Trihalide Perovskite Solar Cell Semiconductors

“…Notably, the band gap ( E g ) is one of the most important integrated aspects of semiconductor physics . UV/Vis and photoluminescent spectroscopic techniques are routinely employed for the accurate determination of E g for solid‐state materials . Experimentalists often refer to this property as the onset of optical absorption .…”

“…[70] UV/Vis and photoluminescent spectroscopic techniques are routinely employed for the accurate determination of E g for solid-state materials. [71][72][73][74] Experimentalists often refer to this property as the onset of optical absorption. [76] It is strongly relatedt ot he Shockley-Queisser limit, which applies to cells with as ingle p-n junction architecture.…”

Band Gap Characterization of Thermally Treated Hybrid Blend ZnPc/CdS Thin Films

“…ZnPc appear a three chief absorption peaks, B band at 305 nm in the UV region and Q bands at 694 nm and 690 nm in visible region [10], the intense visible absorption and ultraviolet B band is due to the electronic transitions from π to π*. The peak around 305 nm of the B-band of as-deposited ZnPc film (this single peak is similar to that noticed in many Pcs [11,12] was shifted to 307, 309 and 310 nm for 1h, 2h and 3h annealing films respectively [13].…”