Phthalocyanine/C60施主-受主电荷转移对中前线轨道能级的取代基级调谐
Substituent-level Tuning of Frontier Orbital Energy Levels in Phthalocyanine/C60 Donor-Acceptor Charge Transfer Pairs
摘要：
我们已经计算了几个低洼的电荷转移（CT）激发态能量的四个非共价结合的二联体组成的磺化锌酞菁耦合到C60。我们的研究结果表明，二-和三磺化系统产生的CT态的最低能量的激发态的系统。与此相反，四磺化ZnPc系统的能量重排导致局部激发低于CT状态的能量，显示可能的失活途径阻碍电荷分离。由于几个不同的供体-受体的相对取向可能共存于有机异质结，我们比较了几个低躺CT状态的端部上的几何形状的二磺化系统，其共面取向对应的能量。计算出的CT激发能对于端对取向比共面结构大~1.5 eV，这主要是由于从共面到端对取向的激子结合能的大幅降低。此外，相对供体-受体取向的变化比供体-受体距离的变化对CT能量有更大的影响。TDDFT计算上的各种磺化酞菁锌供体分子显示出一个显着的分裂的Q-带的四个供体系统中只有一个。我们目前的计算，与以前的实验研究一致，表明化学官能团的系统变化是一个很有前途的途径，为各种物理性质的有机半导体的取代基水平调谐。
英文摘要：
We have calculated several low-lying Charge Transfer (CT) excited-state energies for four non-covalently bound dyads composed of a sulfonated-ZnPc coupled to C60. Our results show that the di- and tri-sulfonated systems yield a CT state as the lowest-energy excited state in the system. In contrast, an energy re-ordering for the tetra-sulfonated ZnPc system leads to local excitations lying lower in energy than the CT state, displaying a possible deactivation pathway obstructing charge separation. Since several different donor-acceptor relative orientations may co-exist at an organic heterojunction, we compare the energetics of a few low-lying CT states for the end-on geometry of a di-sulfonated system to its co-facial orientation counterpart. The calculated CT excitation energies are larger for the end-on orientation in comparison to the co-facial structure by ~1.5 eV, which results principally from a substantial decrease in exciton binding energy in going from the co-facial to the end-on orientation. Furthermore, changes in relative donor-acceptor orientation have a larger impact on the CT energies than changes in donor-acceptor distance. TDDFT calculations on the various sulfonated ZnPc donor molecules show a significant splitting of the Q-band for only one of the four donor systems. Our present calculations, in line with previous experimental studies, show that the systematic variation of chemical functional groups is a promising avenue for the substituent-level tuning of various physical properties of organic semiconductors.
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