The Influence Of Ni/Pd/Pt Dopant On The Optical Gap Of BaTi_1-xCo_xO₃

In view of the low efficiency of photovoltaic devices at present,the development of high-efficiency photovoltaic materials has been a hot research topic.BaTiO₃ is a prototype perovskite ferroelectric material,possessing spontaneous polarization characteristics,which can suppress the recombination of the photoinduced electrons and holes.But its band gap is up to 3.4 eV,which is unfavourable for absorbing visible light.In this thesis,the first-principles method based on density functional theory is employed to explore the influence of Ni/Pd/Pt doping on the optical gap and polarization of BaTi_1-xCo_xO₃,which can provide theoretical guidance for the development of high-efficiency photovoltaic materials.The BaTiO₃ supercells of 2×2×2 and 3×3×3 are constructed to study the influence of different Co/Ni/Pd/Pt doping?substituting Ti atoms?concentration and?Co,Ni?/?Co,Pd?/?Co,Pt?co-doping on the optical gap and polarization of BaTiO₃.It is found that only the band gap values of BaTi_0.875Pd_0.125O₃ and BaTi_0.75Pd_0.25O₃ fall into the range of 1.4 eV and 2.0 eV.The band gap of BaTi_0.875Pd_0.125O₃ is of direct band gap character,and has good self-polarization characteristic,showing that BaTi_0.875Pd_0.125O₃ is a potential high-efficiency photovoltaic material.Perovskite transition metal oxides usually contain oxygen vacancies,which might change their properties.We therefore investigate the effect of oxygen vacancies on the photovoltaic properties of the above-mentioned doping system in further step.It is found that the doping systems of BaTi_0.875Co_0.125O_2.875,BaTi_0.926Co_0.037Ni_0.037O_2.926,BaTi_0.926Co_0.037Pd_0.037O_2.926 and BaTi_0.926Co_0.037Pt_0.037O_2.926 meet the requirements of band gap and polarization for high-efficiency photovoltaic materials.It is expected that our research is of great significance for the development of high-efficiency solar photovoltaic materials based on BaTiO₃.