School of Materials and Energy, Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energies, Southwest University, Chongqing, China.
School of Materials and Energy, Chongqing Key Laboratory for Advanced Materials and Technologies of Clean Energies, Southwest University, Chongqing, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Jan 15;225:117480. doi: 10.1016/j.saa.2019.117480. Epub 2019 Aug 19.
Non-fullerene acceptor based organic bulk heterojunction solar cells have been a hot topic because their power conversion efficiencies have been up to 16.35%. Functionalized 6,13‑bis (trimethylsilyl alkynyl) pentacenes with strong electron withdrawing groups, which can be easily modified to improve charge transport properties and film morphology, seem to be promising soluble non-fullerene pentacene-based organic acceptors. But how the substitutions of electron withdrawing groups influence their electronic structures, then change the absorption spectra and power conversion efficiencies, is still not clear. In this paper, we utilize density functional theory and time-dependent density functional theory to study the effects of substitutions of different electron withdrawing groups (CN, CF, NO) and different positions of these groups in 6,13‑bis (trimethylsilyl alkyl) pentacene molecule on their physical and optical properties. We find that the experimental power conversion efficiencies are positively/negatively correlated with calculated dipole moments/exciton binding energies of these functionalized molecules. The computed results indicate that the molecules substituted with CN group have much larger dipole moment than the others. For the same electron withdrawing group, the dipole moment at the R2 position is generally larger than that at the R1 position. Furthermore, we find that the calculated exciton binding energy of these molecules functionalized at the R2 position is lower than that at the R1 position. In addition, the result of absorption spectra confirm that these functionalized 6,13‑bis (trimethylsilyl alkynyl) pentacenes have stronger absorption strength than C60 in the both visible and the ultraviolet regions.
基于非富勒烯受体的有机体异质结太阳能电池一直是一个热门话题，因为它们的光电转换效率已高达 16.35%。具有强吸电子基团的功能化 6,13-双（三甲基硅基）丙炔基并五苯，可通过易修饰来提高载流子输运性能和薄膜形貌，似乎是很有前途的可溶性非富勒烯并五苯基有机受体。但是，吸电子基团的取代如何影响其电子结构，进而改变吸收光谱和光电转换效率，目前还不清楚。在本文中，我们利用密度泛函理论和含时密度泛函理论研究了不同吸电子基团（CN、CF、NO）取代以及这些基团在 6,13-双（三甲基硅基烷基）并五苯分子中不同位置取代对其物理和光学性质的影响。我们发现实验的光电转换效率与这些功能化分子的计算偶极矩/激子结合能呈正/负相关。计算结果表明，取代 CN 基团的分子具有比其他分子更大的偶极矩。对于相同的吸电子基团，R2 位的偶极矩通常大于 R1 位的偶极矩。此外，我们发现这些在 R2 位取代的分子的计算激子结合能低于在 R1 位取代的分子的激子结合能。此外，吸收光谱的结果证实，这些功能化的 6,13-双（三甲基硅基炔基）并五苯在可见光和紫外光区域均比 C60 具有更强的吸收强度。
