Tuning Photoelectric Properties Of Solar Cell Using First-principles

In recent years,with the rapid energy demand and the environmental destruction,it is urgent to control environmental pollution and develop new energy sources.Solar energy is the most common renewable energy source on the planet.If the solar energy can be fully utilized,our current energy and environmental crisis will be alleviated.The use of solar cells can provide an effective way to collect and store the solar energy.However,many of the currently prepared solar cells contain heavy-metal elements,which is harmful to the environment and health,and besides,there exits some problems such as instability and high costs.Therefore,it is significant to tune the photoelectric properties of solar cell materials for the high-performance and friendly-environmental characteristic.Based on the first-principle calculation method,this thesis focuses on the method of improving the photoelectric conversion rate of solar cells.For the heterostructure CdTe/MoS₂ and the perovskite material RbGe_1-xSn_xI₃,we have investigated their band structures,density of states,effective mass and optical absorption spectrum.The results are as follows:1.The heterojunction CdTe/MoS₂ is constructed,the calculated electronic structure indicates the band gap is 0.64 e V,which is lower than the values of CdTe and MoS₂.And it shows that photogenerated electrons are transferred from the CdTe layer to the MoS₂ layer,which promotes the separation of photogenerated carriers and enhance the photoelectron conversion efficiency.Driven by its narrow band gap,the absorption of this heterojunction can cover the wide range of near infrared,visible and ultraviolet light.In addition,we have also investigated the possibility of the photocatalysis for water splitting to hydrogen,it shows that the CdTe/MoS₂ heterostructure can effectively capture the H₂O molecule and release the H₂molecule,which demonstrates this material has the ability to the catalysis of hydrogen evolution.Our theoretical predictions indicate that the CdTe/MoS₂ heterojunction has wide application prospect of the high-efficiency solar cell and photocatalysis.2.For the doped perovskite material RbGe_1-xSn_xI₃,the influence of the doping ratio and doping position of metal elements on the configuration and electronic properties has been studied.The results show that the band gap of mixed metal perovskites is narrower than that of pure Sn and Ge-based perovskites,and the mixed materials have better mobility of electron and hole.Besides,as an example for investigating the influence of the doping position,for RbGe_0.5Sn_0.5I₃,Sn atoms doped in the equatorial plane have better electronic mobility and optical properties than the other two planes.Our results show that doping metal atoms according to different ratios and positions can be an effective way to regulate photoelectric performance.