Department of Physics, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11623, Saudi Arabia.
Basic Science Department, Faculty of Technology and Education, Helwan University, Saraya El Koba, El Sawah Street, Cairo 11281, Egypt.
Int J Mol Sci. 2024 May 21;25(11):5586. doi: 10.3390/ijms25115586.
One useful technique for increasing the efficiency of organic dye-sensitized solar cells (DSSCs) is to extend the π-conjugated bridges between the donor (D) and the acceptor (A) units. The present study used the DFT and TD-DFT techniques to investigate the effect of lengthening the polyene bridge between the donor N, N-dimethyl-anilino and the acceptor dicyanovinyl. The results of the calculated key properties were not all in line with expectations. Planar structure was associated with increasing the π-conjugation linker, implying efficient electron transfer from the donor to the acceptor. A smaller energy gap, greater oscillator strength values, and red-shifted electronic absorption were also observed when the number of polyene units was increased. However, some results indicated that the potential of the stated dyes to operate as effective dye-sensitized solar cells is limited when the polyene bridge is extended. Increasing the polyene units causes the HOMO level to rise until it exceeds the redox potential of the electrolyte, which delays regeneration and impedes the electron transport cycle from being completed. As the number of conjugated units increases, the terminal lobes of HOMO and LUMO continue to shrink, which affects the ease of intramolecular charge transfer within the dyes. Smaller polyene chain lengths yielded the most favorable results when evaluating the efficiency of electron injection and regeneration. This means that the charge transfer mechanism between the conduction band of the semiconductor and the electrolyte is not improved by extending the polyene bridge. The open circuit voltage (V) was reduced from 1.23 to 0.70 V. Similarly, the excited-state duration (τ) decreased from 1.71 to 1.23 ns as the number of polyene units increased from n = 1 to n = 10. These findings are incompatible with the power conversion efficiency requirements of DSSCs. Therefore, the elongation of the polyene bridge in such D-π-A configurations rules out its application in solar cell devices.
一种提高有机染料敏化太阳能电池（DSSC）效率的有效方法是延长给体（D）和受体（A）单元之间的π共轭桥。本研究使用 DFT 和 TD-DFT 技术研究了延长给体 N，N-二甲基苯胺和受体二氰基乙烯之间的聚烯桥的影响。计算得出的关键性质的结果并不都符合预期。平面结构与增加π共轭连接体有关，这意味着电子从给体有效地转移到受体。当增加聚烯单元的数量时，还观察到较小的能隙、较大的振子强度值和电子吸收红移。然而，一些结果表明，当聚烯桥延伸时，这些染料作为有效染料敏化太阳能电池的潜力是有限的。增加聚烯单元会导致 HOMO 能级升高，直到超过电解质的氧化还原电位，从而延迟再生并阻碍电子传输循环的完成。随着共轭单元数量的增加，HOMO 和 LUMO 的末端叶继续收缩，这影响了染料内部分子内电荷转移的容易程度。在评估电子注入和再生效率时，较短的聚烯链长度产生了最有利的结果。这意味着通过延长聚烯桥不会改善半导体导带和电解质之间的电荷转移机制。开路电压（V）从 1.23 降低到 0.70 V。同样，随着聚烯单元数量从 n = 1 增加到 n = 10，激发态持续时间（τ）从 1.71 降低到 1.23 ns。这些发现与 DSSC 的功率转换效率要求不兼容。因此，在这种 D-π-A 构型中延长聚烯桥排除了其在太阳能电池器件中的应用。
