Study On Transport Properties Of TiO₂ In Perovskite Solar Cells

In the past decade,perovskite solar cells have been more attractive in power conversion efficiency?PCE?than other solar cells.It has been the best candidates for the future use of renewable solar energy sources,and it is one of the research focuses in the field of solar cells.As the electron transport layer of the perovskite solar cell,TiO₂ has problems such as excessive band gap.This makes electrons in the light absorbing layer inject and transfer difficult,then hinders the improvement of PCE of the device.The experimental results show that electrons are easier to inject and transfer into yttrium-doped TiO₂,indicating that doping can improve the efficiency of photoelectric conversion.In this thesis,the real-time electronic structure calculator?RESCU?based on first-principles is used to simulate the electron transport properties of CH₃NH₃PbI₃and TiO₂.The hybrid density functional?HSE06?and the generalized gradient approximation?GGA?with PBE functional are compared by calculation results of band structures.Band gap calculation results show that the former is more accurate.At the same time,density of states,ionization energy and mobility of them are calculated by hybrid density functional theory.The calculated results are in agreement with the experimental and theoretical values in the relevant literature.After the doping of the rutile TiO₂,the band gap is reduced,and the electron mobility is decreased.The calculation results of electrostatic potential and electronic structure of the heterojunction of the titanium dioxide and CH₃NH₃PbI₃ prove that the energy levels between the two are well matched.Although the mobility of yttrium-doped TiO₂ is reduced,the transmission coefficient of electrons is increased more,which is more conducive to the transmission of electrons and improves the photoelectric conversion efficiency.