Improvement of the Physical and Technical Characteristics of the Thin-Film Solar Cells under their Modification by the Plasmonic Nanoparticles

This work deals with the study of such an important task of plasmonic photovoltaics as the improvement of thin-film solar cells by introducing metal nanoparticles into their absorbing layer. The frequency dependences of photocurrent amplification, radiation efficiency and electric field amplification in the neighborhood of the nanoparticles, as well as an expression for volt-ampere characteristic of Schottky barrier formed at the boundary of metallic nanoparticle and the semiconductor absorbing layer are obtained. The mathematical model, proposed in this work, takes into account all mechanisms of electron relaxation in metallic nanoparticle. The calculations have been performed for the case of Ag and Pt nanoparticles embedded into TiO2 and Si layer. The fact of the significant amplification, of photocurrent with decreasing the thickness of the absorbing layer and increasing the radius of embedded plasmonic nanoparticles has been established. In this case, the spectral range of thin-film solar cells is determined by the properties of the semiconductor, primarily by the width of the forbidden zone of the absorbing layer. The calculations showed the weak size dependence of the frequency of the surface plasmonic resonance and the strong dependence of the position of the maxima of the spectral characteristics on the material properties of the nanoparticles and the absorbing layer. It has been demonstrated the advantage of silver nanoparticles over platinum nanoparticles, as they provide greater radiation efficiency at the same frequencies. The results of the calculations of the frequency dependences of the amplification of electric fields in the neighborhood of plasmonic nanoparticles indicate its growth with decreasing radius of platinum nanoparticles, while the highest maximum value of the amplification will be in the neighborhood of silver nanoparticles of intermediate sizes, which is explained by the weakening of the process of electron relaxation in silver nanoparticles of such sizes. The sharp (3-4 orders of magnitude) increase in the current in the modified solar cells compared to conventional ones at voltages exceeding the Schottky barrier is shown, which is explained by the excitation of plasmonic resonances on the surface of metallic nanoparticles.