Molecular Engineering of Quinoxaline-Based D–A−π–A Organic Sensitizers: Taking the Merits of a Large and Rigid Auxiliary Acceptor

Abstract

The continuing efforts of creating novel D-A-π-A structured organic sensitizers with excellent optoelectronic properties have resulted in substantial improvement of power conversion efficiency (PCE) as well as stability of dye-sensitized solar cells (DSSCs). Here, we report a new molecular engineering strategy for enhancing optical gain and improving excited-state features in D-A-π-A structured organic sensitizers by improving the conjugation size and rigidity of the auxiliary acceptor functional group. A series of phenanthrene-fused-quinoxaline (PFQ)-based D-A-π-A organic sensitizers (WS-82, WS-83, and WS-84) are designed and synthesized for applications in DSSCs. Compared to 2,3-diphenylquinoxaline (DPQ)-based dye IQ-4, PFQ dyes show extended absorption spectra and improved open-circuit voltage performance. Upon a systematical engineering of alkyl chains and π-spacer structure, the unfavorable issues of PFQ dyes including low solubility and high energy barrier in intramolecular charge transition are successfully eliminated. When applied in iodine electrolyte-based DSSCs, the best performing PFQ dye WS-84 shows a PCE of 10.11%, which is much higher than that of our previous champion DPQ dye IQ-4 under the same conditions.

Comparison in optoelectronic properties of triphenylamine-imidazole or imidazole as donor for dye-sensitized solar cell: theoretical approach

“…The use of multi-donors has been proven as a good strategy for delaying charge recombination and enhancing the open-circuit photovoltage [17,18]. Among all, several models multidonor have been synthesized or designed theoretically, D-Dπ-A, (D-π-A) 3L2, in order to improve the performance and the efficiency of the dye to absorb more energy from solar spectrum [19][20][21][22]. The computation tools have contributed a lot in this field in studying the different molecular designs, to deepen in optoelectronic studies of the different molecules in order to be able to present them as effective candidate dyes [23,24], as well as to propose them to the experimenter to be synthesized it.…”

“…The donor may be quinoxaline [21], quinoline [25] phenothiazine, phenoxazine [26,27], or triphenylamine [28].…”

Comparison in optoelectronic properties of triphenylamine-imidazole or imidazole as donor for dye–sensitized solar cell: Theoretical approach

“…The use of multi-donors has been proven as a good strategy for delaying charge recombination and enhancing the open-circuit photovoltage [17,18]. Among all, several models multidonor have been synthesized or designed theoretically, D-Dπ-A, (D-π-A) 3L2, in order to improve the performance and the efficiency of the dye to absorb more energy from solar spectrum [19][20][21][22]. The computation tools have contributed a lot in this field in studying the different molecular designs, to deepen in optoelectronic studies of the different molecules in order to be able to present them as effective candidate dyes [23,24], as well as to propose them to the experimenter to be synthesized it.…”

“…The donor may be quinoxaline [21], quinoline [25] phenothiazine, phenoxazine [26,27], or triphenylamine [28].…”

Solvent Effects on Intra-/Intermolecular Charge Transfer in Indoloquinoxaline-Based Dyes

“…To improve the excited state and optical properties of the D–A−π–A structure of the organic dyes, a new molecular engineering strategy suggests itself, through the extension of the conjugation size and rigidity of the auxiliary acceptor functional group. For example, a series of phenanthrene-fused-quinoxaline (PFQ) based D–A−π–A organic sensitizers were studied . In comparison to a 2,3-diphenylquinoxaline- (DPQ-) based dye, IQ-4 and PFQ dyes show an extended absorption spectrum and higher V OC .…”