FA1-xCsxPbI3-yBry钙钛矿材料优化及太阳电池性能计算

Simulation and property calculation for FACsPbIBr:Structures and optoelectronical properties

甲脒铅碘钙钛矿(FAPbI3)因其优异的光电性能而成为新兴太阳电池最具潜力的候选材料,但是稳定性较差成为制约其发展的主要瓶颈.通过离子掺杂可以有效地改善FAPbI3的稳定性,如通过共掺杂Cs^+和Br^-形成FA1-xCsxbI3-yBry钙钛矿材料,其耐热及耐水稳定性得到显著改善.本文利用第一性原理计算了FA1-xCsxPbI3-yBry(x=0.125,y=0-0.6)体系的几何结构、电子结构和光学性质.通过分析发现Cs^+和Br^-的掺入使得体系能量降低,FA0.875Cs0.125PbI2.96 Br0.04最稳定.利用等效光学导纳法模拟计算了平面结构钙钛矿太阳电池的吸收率、载流子收集效率、外量子效率、短路电流密度、开路电压和伏安特性.对于FA1-xCsxPb I3-yBry钙钛矿太阳电池,当x=0.125,y=0.04,厚度为0.5—1.0μm时,电池的短路电流密度均为24.7mA·cm^-2,开路电压为1.06 V.结果表明Cs^+和Br^-的共掺杂在没有降低电池短路电流的同时提高了体系的稳定性,可为实验上制备高效稳定的钙钛矿太阳电池提供理论参考.

Formamdinium lead triiodide(FAPbI3)perovskite has developed as a promising candidate in solar cells for its excellent optoelectronic property.However,the poor environmental stability is still a critical hurdle for its further commercial application.Element doping is an effective method of improving the stability of FAPbI3 materials.It has been reported that the FA1-xCsxPbI3-yBry stability for heat and water resistance were greatly improved by Cs cations and Br anions co-doping.In this study,we perform first-principles calculations to systematically investigate the crystal structures,electronic structures,and optical properties of FA1-xCsxPbI3-yBry.We obtain several stable crystal structures of FA1-xCsyPbI3-yBry(x=0.125,y=0-0.6)in the cubic phase for different ratios of Cs cations to Br anions.By analyzing the structures of these mixed ion perovskites,it is revealed that the lattice parameters decrease linearly with the increase of concentration of Cs cations and Br anions,which is consistent with previous experimental result.In this work,the formation energy difference(AE)is calculated and our results show that the mixing of Cs cations and Br anions could increase the thermodynamic stability compared with pure FAPbI3.The FA0.875Cs0.125PbI2.96Br0.04 is found to be the most stable in all composites investigated.Furthermore,the band gap,hole and electron effective mass increase with increasing proportion of Br anions,indicating an effective strategy for extending the absorption range of FAPbI3 perovskites into the ultraviolet of the solar spectrum,thereby affecting the carrier transport mechanism in this material.Density of states(DOS)analysis indicates that the DOS of valence band edge increases with increasing proportion of Br anions and enhancing transitions between the valence and conduction bands.Finally,the absorption rate,carrier collection efficiency,external quantum efficiency,short-circuit current density,open circuit voltage and volt-ampere characteristics for the planar structure perovskite solar cell are analyzed by the equivalent optical admittance method.For the FA1-xCsxPbI3-yBry(x=0.125,y=0.04 thickness=0.5-1.0μm)solar cell,the short-circuit current density and the open circuit voltage are estimated at about 24.7 mA·cm^-2 and 1.06 V.It is demonstrated that the co-doping Cs cations and Br anions can improve the stability of the system without reducing short-circuit current density,which may provide some theoretical guidance in preparing the perovskite solar cells with high efficiency and excellent stability.