Studying the surface morphology, linear and nonlinear optical properties of manganese (III) phthalocyanine chloride/FTO films

Highlights

• MnPcCl film were prepared by the thermal vacuum evaporating technique.

• Surface morphology shows that the MnPcCl film is formed by spherical nanoparticles.

• The MnPcCl film deposited on the FTO revealed a high optical laser limitation.

Abstract

Scientific review of laser protective materials is currently primarily focused on improving linear transmittance and developing the optical limiting ability. Due to its unique large π electronic conjugated structure, phthalocyanine has become a successful optical limiting material. Thin films of manganese (III) phthalocyanine chloride (MnPcCl) were formed on FTO substrates using traditional thermal deposition techniques. The X-ray diffraction demonstrated that there is an amorphous structure for MnPcCl films. AFM's surface morphology shows that the MnPcCl film is homogeneous and formed by spherical and elliptical nanoparticles. The thickness dependences of both linear and nonlinear optical properties of MnPcCl films were also investigated via UV–Vis-IR measurements. The absorption coefficient examination indicated that the films were distinguished by an indirect transition with two energy gaps. The power of the He–Ne (633 nm) and green (533 nm) lasers were used to estimate optical limiting behavior. The MnPcCl film deposited on the FTO revealed a high optical laser limitation that could be acceptable for different nonlinear optical devices, like laser filters.

Introduction

In many recent works, Phthalocyanine (Pc) compounds have attracted significant interest in several scientific fields such as medicine [1], optical communication [2], chemical sensors [3], and solar cells [4]. These compounds have high radiation resistance, significant and easily adapted linear/nonlinear optical properties possess many scientific applications, including materials science, optoelectronic, and photonic device fabrication [5]. Furthermore, they display high chemical and thermal stability, increasing the possibility of using this compound as optical sensors, increasing surface acoustic waves, catalysts, biological imaging, and therapy.

However, due to their low solubility and the formation of aggregates in solution and solid films, several researchers study the modification of adding different metals to Pc's central [6]. It is well known that metal phthalocyanine (MPc) compounds exhibit excellent nonlinear optical (NLO) properties due to the remarkably symmetrical spatial configuration and overall π-electronic conjugation structure. In literature, several metals such as Zinc, Lead, Copper, Gallium, etc., are integrating into Pc's side group to study the change of optical and electrochemical properties [7,8]. Various studies have proven that Pc's optical properties and applications are affected by the central metal's nature [9]. Farag et al. [10] studied the effect of central metals (Cu (II), Zn (II), Co (II), Pb (II), and Mn (III)) in the metal-free Pc compound. They showed that the surface morphology depends on the kind of metal complex. Several optical parameters were analyzed and showed that the nanocrystalline MPc thin films could be favorable for optoelectronic applications.

On the other hand, researchers have been interested in the phthalocyanine compounds with metal chloride because they exhibit distinctive optical properties [[11], [12], [13]] and photoelectric behavior worthy of attention [14,15]. The optical properties of AlPcCl [11] and GaPcCl [12,13] films have been studied. These films displayed indirect permissible interband transitions, and different dispersion and absorption parameters were evaluated. Besides, electrochemical, dielectric, electrical, and measurements of AlPcCl have been performed, where cyclic voltammetry was utilized to calculate the energy gap and was found to be 1.42 eV [16]. Rajesh and Menon investigated the electrical conductivity of MnPcCl films [17]. They came to the conclusion that oxygen has a significant influence on electrical parameters. There is a scarcity of scientific research on the properties of MnPcCl films, particularly their optical properties, which are greatly important for photovoltaic applications.

In General, any electronic or photoelectric applications require a transparent electrode and usually used Fluorine Doped Tin Oxide (FTO) coated glass substrate. FTO has a higher conductivity, good optical transmittance, and reflection in the infrared range [18]. For these excellent properties, FTO would be suitable for deposited MnPcCl films. Thus, the present study aims to deposit MnPcCl films on FTO by the conventional thermal deposition technique. The thickness influence of MnPcCl film on optical properties will be analyzed. MnPcCl films' significant parameters such as refractive index, high-frequency dielectric constants, real and imaginary parts of dielectric constants, absorption index, and lattice dielectric constants were measured and interpreted. Finally, the optical limiting of MnPcCl film was studied via two laser wavelength sources (532 nm and 638 nm) for laser filters.