title: Constructing high-efficiency D-A-π-A-featured solar cell sensitizers: a promising building block of 2,3-diphenylquinoxaline for antiaggregation and photostability.
abstract: Controlling the sensitizer morphology on a nanocrystalline TiO2 surface is beneficial to facilitating electron injection and suppressing charge recombination. Given that the grafted alkyl chain on a π-bridge thiophene segment for preventing π aggregation can deteriorate its intrinsic photostability, we incorporate a promising building block of 2,3-diphenylquinoxaline as the additional acceptor to construct a novel D-A-π-A-featured dye IQ4, which exhibits several characteristics: (i) efficiently decreasing the molecular HOMO-LUMO energy gap by extending its absorption bands; (ii) showing a moderate electron-withdrawing capability for an ideal balance in both promising photocurrent and photovoltage; (iii) endowing an ideal morphology control with strong capability of restraining the intermolecular aggregation and facilitating the formation of a compact sensitizer layer via two twisted phenyl groups grafted onto the quinoxaline unit. The coadsorbent-free dye-sensitized solar cell (DSSC) based on dye IQ4 exhibits very promising conversion efficiency as high as 9.24 ± 0.05%, with a short-circuit current density (Jsc) of 17.55 mA cm(-2), an open-circuit voltage (Voc) of 0.74 V, and a fill factor (FF) of 0.71 under AM 1.5 illumination (100 mW cm(-2)). IQ4-based DSSC devices with an ionic liquid electrolyte can keep constant performance during a 1000 h aging test under 1 sun at 60 °C. Because of spatial restriction, the two phenyl groups grafted onto the additional electron-withdrawing quinoxaline are demonstrated as efficient building blocks, not only improving its photostability and thermal stability but also allowing it to be a successful antiaggregation functional unit. As a consequence, the incorporated 2,3-diphenylquinoxaline unit can realize a facile structural modification for constructing organic coadsorbent-free D-A-π-A-featured sensitizers, thus paving a way to replace the common, stability-deleterious grafted alkyl chain on the thienyl bridge.
authors.affiliation: Shanghai Key Laboratory of Functional Materials Chemistry, Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, People's Republic of China.
authors.forename: Kai
authors.initials: K
authors.lastname: Pei
authors.forename: Yongzhen
authors.initials: Y
authors.lastname: Wu
authors.forename: Ashraful
authors.initials: A
authors.lastname: Islam
authors.forename: Qiong
authors.initials: Q
authors.lastname: Zhang
authors.forename: Liyuan
authors.initials: L
authors.lastname: Han
authors.forename: He
authors.initials: H
authors.lastname: Tian
authors.forename: Weihong
authors.initials: W
authors.lastname: Zhu