Impact of the Interfacial Molecular Structure Organization on the Charge Transfer State Formation and Exciton Delocalization in Merocyanine:PC₆₁BM Blends

Abstract

The intermolecular charge transfer (CT) exciton in the merocyanine:[6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) system induced by the molecular geometry is investigated. The CT state, localized on the merocyanine domain, was experimentally observed in the transient spectra and modeled via DFT/TDDFT calculations. A relationship between molecular geometry at the donor/acceptor interface and the delocalization of the CT exciton was identified. It was found that different alkyl side chains of merocyanine can be used to tune the formation of H-aggregates by means of better intermixing with PC 61 BM. Moreover, we observed that high H aggregation increases the charge delocalization and improves the efficiency and carrier transport properties of the merocyanine-based bulk heterojunction solar cell.

Morphology Determines an Efficient Coherent Electron Transport for Push–Pull Organic Semiconductors Based on Triphenylamine and Dicyanovinyl Groups

“…Currently, there is no consensus about which molecular orientation leads to a more efficient charge generation when comparing edge- and face-on stacking modes [ 5 , 24 ]. We found that coherent charge transmission was higher along the edge-on stacking direction (P1) of compound 4 .…”

“…The above is due to the intermolecular arrangement of the molecules that compose the active layer of organic solar cells. This arrangement affects the exciton diffusion and the charge generation and recombination [ 3 , 4 , 5 , 6 ]. The morphology of the active layer then influences the performance of organic solar cells.…”

Halogenation of the Side Chains in Donor‐Acceptor Based Small Molecules for Photovoltaic Applications: Energetics and Charge‐Transfer Properties from DFT/TDDFT Studies

“…However, it has been verified in many cases that face-on arrangement increases the electron coupling and contributes the most to the charge transport in the donor/acceptor bi-molecular systems. [58][59][60][61][62][63] Therefore, we have chosen to use face-on models for our systems. In the above optimizations, Grimme's D3 version of dispersion correction was also included.…”

“…[104][105]107] It has been highlighted that better device performance upon halogenation may not be due to energetics alone, and it is also morphology dependent. [58,[62][63] Experimentally controlling the blend morphology at the interface is a difficult task. Computational modeling of the interface morphology is even a bigger challenge.…”