The First-Principle Study On Nontoxic Gold-based Perovskite Solar Cells Absorbers

Perovskite solar cells because of superior optoelectronic properties: suitable band gaps,high tolerance factor,long carrier diffusion length,low exciton binding energy,balanced electron and hole mobility.So the photoelectric conversion efficiency from the 3.8% to 25.2% now,such a fast development speed makes it gradually become a star material in the field of solar cells.Though the perovskite solar cells have good prospects,there are also some shortcomings,especially the use of heavy metal lead,which is highly toxic and seriously pullulates the environment and harms human health.Meanwhile,the use of expensive metal elements also make it difficult to realize industrialization.In order to solve the above problems of perovskite solar cells,this paper is based on the first principle,using density functional theory,we have investigated the geometry structures,electronic structures and optical absorption coefficients of perovskite solar cell absorption layer materials.The results are as follows:Firstly,though our calculation,the results show that Cs₂Au₂I₆ is a perovskite solar cell absorption layer material with good photoelectric conversion efficiency.It has a suitable HSE band gap（1.167 e V）and a sharp light absorption coefficient（～105cm-1）.At the same time,the average effective mass of carriers which are beneficial to electron and hole transport is 0.362m0 and 0.371m0,respectively.It is also proved to be stable by decomposition enthalpy,Schmidt tolerance factor and phonon spectrum.There,our calculation can provide strong evidence for the theoretical research and experiment of lead-free perovskite solar cell absorption layer materials.Secondly,our research found that Cs₂AgAuI₆ is a non-toxic,inexpensive and ideal perovskite solar cell absorption layer material.It has a proper HSE band gap（1.289 e V）and a sharp absorption coefficient（～105 cm-1）.Meanwhile,the average effective mass of carriers which are beneficial to electron and hole transport is 0.346m0 and 0.31m0,respectively.And decomposition enthalpy,Schmidt tolerance factor and the phonon spectra show that it is very stable.Because Cu d-orbital energy is higher than that of Ag and Au,Cu Au-based perovskite is not stable.This can be seen from the phonon spectra.Therefore,our calculations could provide strong evidence for the experimental to synthesis the lead-free and low-cost perovskite solar cell absorber materials.