The effect of X-rays and gamma rays on nanocomposite materials

Abstract

As an alternative to classical silicon electronics, organic electronics has grown rapidly. The most promising and industrially developed areas of the application of organic semiconductor nanostructures are light-emitting devices and photodetectors. Organic solar cells, despite the inadequate efficiency (about 10-12%), have many advantages, such as a large area, low weight, the ability to be applied on flexible substrates, simple technology, and potentially low cost. Thus, photovoltaics based on organic semiconductors and their composites have rapidly developed compared to other types of solar cells. The baseline of such solar cells are donor-acceptor mixtures, which can be a mixture of materials with different molecular weight. To ensure the realization of a bulk heterojunction or an ordered system of molecular complexes, a branched donor-acceptor mixture is required. A bulk heterojunction allows the separation of the exciton formed upon absorption of a quantum of light. The study of optical properties, photoluminescence, in particular, is one of the most informative methods on the electronic structure of materials. The study and analysis of the process of luminescence in nanocomposites allow conclusions about the exciton migration and the efficiency of the achievement by carriers of a donor-acceptor interface.

The application area of organic optoelectronic devices is growing. There are prospects of space applications of organic optoelectronic devices in special conditions. Thus, the question arises about the stability of the properties of organic components under the influence of hard radiation. However, exposure to ionizing radiation can modify and improve the properties of organic semiconductors. In addition, there is a poignant issue of creating radiation sensors based on organo-inorganic nanocomposites. Gamma and X-ray radiation interacts with material by electronic excitation and ionization. This process in organic materials leads to the appearance of excited molecules, ions, free radicals, and the rupture or formation of covalent bonds. In oxygen atmosphere, this can cause the oxidation of fragments. Thereby, changes in the properties of organic materials under the influence of gamma and Х-ray radiation can lead to the deterioration of parameters, or to their modernization.

The aim of the present work is to obtain new data on the structure, surface morphology, spectral dependence of photoluminescence, and the electronic structure of the main types of nanocomposite thin films used in organic photovoltaic structures, as well as to study the effect of gamma radiation on them. The main types of analysed organic semiconductor nanocomposites are:

(1) C60/CdTe, as a typical organo-inorganic composite for solar receivers.

(2) Porphyrin ZnTPP/C60, as a typical low molecular weight composite with molecular complexes.

(3) Nanocomposites based on the conductive polymer MEH-PPV with various types of acceptor inclusions, namely: MEH-PPV/C60, MEH-PPV/Н2TPP, MEH-PPV/Qd (PbS) and MEH-PPV/nanodiamonds.