MTDTPY·TCNQ及MTDTPY·CHL电荷转移复合物晶体的电子能带结构及其与导电性能关系的研究

Electronic Energy Band Structure of Charge Transfer Complex Crystals MTDTPY·TCNQ and MTDTPY·CHL and the Relations Between the Band Structure and the Electrical Conductivity

用紧束缚近似的EHMO方法对α-MTDTPY·TCNQ(1)、β-MTDTPY·TCNQ(2)及MTDTPY·CHL(3)三种电荷转移复合物晶体的电子能带进行了计算.在1中,电子施体(D)分子MTDTPY及受体(A)分子TCNQ形成交替重叠的一维分子柱(M),柱间无净电荷转移.能隙.E_G=0.15 eV,载流子的产生主要来自热激发.在2及3中,电子施体(D)MTDTPY及受体(A)TCNQ及CHL分子分别形成相对独立的D及A一维分子柱,载流子的产生主要来自柱间的电荷转移.由电子能带结构及关于载流子迁移的Frohlich-Sewell公式,得出上述三种晶体的室温电导率之比为σ_1∶σ_2∶σ_3=3.72×10^(-10)∶1∶1.15,与实验事实基本一致.关于各分子柱对σ的贡献,2中D柱∶A柱～10~3∶1;3中D柱∶A柱～2∶1.根据计算结果,本文还对载流子的迁移机理进行了讨论.

The electronic energy bands of charge transfer complexes α-MTDTPY·TCNQ(1), β-MTDTPY·TONQ (2) and MTDTPY·CHL (3) were calculated by tight binding EHMO. In 1, the electron donor, molecule MTDTPY, and the electron acceptor, molecule TCNQ, form a quasi one-dimensional mtxed molecular column with alternative packing, and there is no net intereclumn charge transfer. The energy gap E=0.15eV. The charge carriers are created by thermo-exciting from band E_(Ho) to E_(LU). As for 2 and 3, the electron donor, molecule MTDTPY and electron acceptor, molecules TCNQ and OHL appear in relatively separated quasi one-dimensional molecular columns respectively. Charge carriers mainly come from inter-column charge transfer. Based on the calculated structure of energy bands and according to the equation of the migration of charge carriers of Frohlich-Sewell, the proportion of the room temperature electrical conductivities for these crystals is σ_1: σ_2: σ_3=3.75×10^(-10):1:1.15, and it is fundamentaly coincide with the relevant experimental results. In 2 the ratio of contributiong of molecular column MTDTPY (D) and TCNQ (A) to electrical conductivity is σ_D:σ_A=10~3:1, and for 3, the corresponding ratio of MTDTPY (D) and CHL (A) is σ_D:σ_A=2:1. Besides, the migration mechanisms of charge carriers of these crystals have been discussed.