Bi替代CH_(3)NH_(3)Pb_(1-x)Bi_(x)Br_(3)钙钛矿实现带隙调控

Band Gap Regulation of CH_(3)NH_(3)Pb_(1-x)Bi_(x)Br_(3) Using by Bi Substitution

通过Bi^(3+)代替Pb^(2+)离子对CH_(3)NH_(3)PbBr_(3)进行n型掺杂,使用Materials Studio软件的CASTEP模块构建出CH_(3)NH_(3)Pb_(1-x)Bi_(x)Br_(3)(x=0,0.25,0.50,0.75,1.00)五种结构位形,基于第一性原理并将GGA+PBE作为关联函数对其结构进行几何优化与物理性质研究.结果表明:随着Bi含量的增加,CH_(3)NH_(3)Pb_(1-x)Bi_(x)Br_(3)带隙有逐渐减小的趋势,特别是当x=0.50时,实现了半导体向导体的转变;当Bi替代含量为0.25时,CH_(3)NH_(3)Pb_(0.75)Bi_(0.25)Br_(3)具有可以吸收可见光的能带结构;Bi与Pb的6p电子占据导带底,s电子占据价带顶,s电子与Br的p电子存在较强的轨道耦合;Bi(6s^(2)p^(3))比Pb(6s^(2)p^(2))多一个p电子,随着Bi替代量的增加,多出的p电子从浅掺杂逐渐向重掺杂过渡,准能级逐渐增加,最终填满整个带隙,导带与价带交联进而实现半导体向导体的转变.

The n-type doping of CH_(3)NH_(3)PbBr_(3) perovskite is carried out by Bi^(3+)substitution for Pb^(2+) cations.Five structural configurations(x=0,0.25,0.50,0.75,1.00)are constructed by CASTEP module in Materials Studio software.Based on the first principles,GGA+PBE is used as the correlation function to study the geometric optimization and physical properties.The results show that:with the increase of Bi content,the band gap of CH_(3)NH_(3)Pb_(1-x)Bi_(x)Br_(3) tends to gradually decrease,especially when x=0.50,the transition from semiconductor to conductor is realized.When the Bi substitution content is 0.25,CH_(3)NH_(3)Pb_(0.75)Bi_(0.25)Br_(3) can absorb the visible light.Bi and Pb’s 6p electrons occupy the conduction band minimum(CBM),while s electrons occupy the valence band maximum(VBM).Bi(6s^(2)p^(3))has one more p electron than Pb(6s^(2)p^(2)),with the increase of Bi substitution content,the extra p electron gradually overgoes from shallow doping to heavy doping,and the quasi-energy level gradually increases,finally filling the entire band gap,and then the conduction band and valence band are cross-linked to realize the transformation from semiconductor to conductor.