Enhancing Photoinduced Charge Separation through Donor Moiety in Donor–Acceptor Organic Semiconductors

Abstract

Three systems were designed, synthesized, and characterized to understand decay processes of photoinduced charge separation in organic semiconductors that are imperative for efficient solar energy conversion. A styrene-based indoline derivative (YD) was used as donor moiety (D), a triazine derivative (TRC) as the first acceptor (A1), and 9,10-anthraquinone (AEAQ) as a second acceptor (A2) in constructing two systems, YD-TRC and YD-TRC-AEAQ. The lifetime of the photoinduced charge-separated states in YD-TRC, a D–A1 system, was found to be 215 ns and that in YD-TRC-AEAQ, a D–A1–A2 system, to be 1.14 μs, a 5-fold increase with respect to that of the YD-TRC. These results show that YD is a more effective donor in YD-TRC and YD-TRC-AEAQ systems at forming long-lived charge-separated states compared to a previously reported atriphenylamine derivative (MTPA) that generated charge-separated states with a lifetime of 80 ns in MTPA-TRC and 650 ns in MTPA-TRC-AEAQ. The third system was constructed using a metal-free porphyrin derivative (MHTPP) to form a MHTPP-TRC-AEAQ structure, a D–L (linker)–A system with a charge separation lifetime less than 10 ns. Therefore, the D–A1–A2 architecture is the best at generating long-lived charge-separated states and thus is a promising design strategy for organic photovoltaics materials.

Characterization of photo-induced electron and hole transfer in a porphyrin based ambipolar organic molecule with cascade energy levels

“…A series of D-A 1 -A 2 systems were reported, with the triphenylamine (MTPA) or indoline (YD) derivative as a donor, s-triazine derivative (TRC) as the first acceptor (A 1 ), and anthraquinone derivative (AEAQ), or two perylene bisimide derivatives (PDI and PBI) as the second acceptors (A 2 ), and could be denoted as D-TRC-A 2 systems. The charge-separated states in MTPA-TRC-AEAQ system is elongated to 650 ns, more than 8 times of that in the MTPA-TRC, a simple D-A architecture (80 ns) [34,36], and the further studies suggest that charge separation efficiency and lifetime of charge-separated states may be controlled by changing the donor and second acceptor of MTPA-TRC-AEAQ [34,36,38,40]. The aforementioned ambipolar organic molecules have cascade energy levels and similar photophysical processes to generate photo-induced charge-separated states which relate to the photovoltaic performance of organic solar cells [34,37,38].…”

“…The charge-separated states in MTPA-TRC-AEAQ system is elongated to 650 ns, more than 8 times of that in the MTPA-TRC, a simple D-A architecture (80 ns) [34,36], and the further studies suggest that charge separation efficiency and lifetime of charge-separated states may be controlled by changing the donor and second acceptor of MTPA-TRC-AEAQ [34,36,38,40]. The aforementioned ambipolar organic molecules have cascade energy levels and similar photophysical processes to generate photo-induced charge-separated states which relate to the photovoltaic performance of organic solar cells [34,37,38]. In this work, metal-free tetraphenyl porphyrin module (HTPP) as the second electronic acceptor was firstly introduced into the MTPA-TRC system, which utilized 4,4 0 -dimethyl-4 00 -styryl-triphenylamine (MTPA) as donor and TRC as the first acceptor based on the substitution of chlorine at triazine.…”

Effects of heterocyclic ring and amino‐ethyl‐amino group on the electronic and photophysical properties of a triphenylamine‐pyrimidine dye

“…Since nonconjugated chains can inhibit the back charge transfer and improve the charge separation efficiency of D-A systems, the introduction of nonconjugated chains as a bridge between the donor and the acceptor has attracted widespread attention of researchers. [37][38][39] In addition to these heterocyclic groups, between the donor and acceptor of the triphenylamine-s-triazine binary electron transfer systems nonconjugated alkyl-amino groups of different lengths were introduced. Studies showed that all the systems after the introduction of nonconjugated chains indeed show long-lived charge-separated states.…”

Tuning Intramolecular Charge Transfer through Adjusting Hydrogen Bonding by Anions

“…These intramolecular processes could lead to the transient alternation of the electronic properties such as energies of electronic state, electron density distribution and dipole moments, which could tune the emission color by both covalent modifications of the fluorescence chromophores and its non‐covalent interactions with the surrounding micro‐environment . Therefore, molecules capable of ICT have practical and potential applications in sensing,– nonlinear optics, catalysis, semiconducting, thermochromism, organic light‐emitting materials…”

“…[1] These intramolecular processes could lead to the transient alternation of the electronic properties such as energies of electronic state, electron density distribution and dipole moments, which could tune the emission color by both covalent modifications of the fluorescence chromophores and its non-covalent interactions with the surrounding micro-environment. [2] Therefore, molecules capable of ICT have practical and potential applications in sensing, [3,2a-c,4] nonlinear optics, [5] catalysis, [6] semiconducting, [7] thermochromism, [8] organic light-emitting materials. [9] The optical and electronic properties of perylene bisimide (PBI) dyes have been tuned by substitution, [1g,10] controlling the local π-π stacking arrangements, [11] and supramolecular assembly with electron donating/accepting molecules.…”