Jingyu Qian

Reversible Multistimuli-Response Fluorescent Switch Based on Tetraphenylethene–Spiropyran Molecules

Two tetraphenylethene (TPE)-functionalized spiropyran (SP) molecules with very similar structure were designed and synthesized. The two molecules exhibit aggregation-induced emission (AIE) properties, as well as multistimuli-responsive color-changing properties, such as photochromism and acidchromism. The investigation of their different photochromic and acidchromic characteristics and dual-response fluorescent switch during isomerization indicated that the different link position between TPE and SP will significantly affect the extended π-conjugated system, resulting in completely different photochromic and acidchromic properties.

Solution-processable two-dimensional conjugated organic small molecules containing triphenylamine cores for photovoltaic application

Two solution-processable two-dimensional conjugated organic small molecules based on triphenylamine (TPA) cores, TPA-BT-C8 and TPA-3Th, were designed and synthesized. As to TPA-BT-C8, two arms of the TPA core are symmetrically connected with a thiophene donor group and a benzothiadiazole acceptor group, while the third arm consists of a strong acceptor group of 2-(5,5-dimethylcyclohex-2-en-1-ylidene)malononitrile (DCM) connected through a trans double bond with the TPA core. For TPA-3Th, two arms of its TPA core are composed of only donor group, terthiophene, whereas the third arm consists of an acceptor group of cyano-n-octyl acetate connected through a trans double bond with the TPA core. The investigation indicated that TPA-BT-C8 has a lower energy band gap and wider absorption than TPA-3Th due to the strong intramolecular charge transfer effect in TPA-BT-C8. The two molecules have a deep highest occupied molecular orbital (HOMO) energy level. Bulk heterojunction photovoltaic devices were fabricated using TPA-BT-C8 or TPA-3Th as the donor and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as the acceptor. All the devices have a high open-circuit voltage (Voc) of about 0.9 eV. Devices based on TPA-BT-C8 have a much higher short circuit current (Jsc) (8.47 mA cm−2) and power conversion efficiency (PCE) (2.26%) than devices based on TPA-3Th (4.32 mA cm−2, 1.21%), resulting from wider solar light absorption of TPA-BT-C8 and better compatibility and film-formation ability of TPA-BT-C8 with PCBM than TPA-3Th. Incident photon-to-electron conversion efficiency (IPCE) spectra also confirmed that TPA-BT-C8 based devices have a wider and red-shifted response range than TPA-3Th based devices, which leads to a higher performance of the former devices.

A theoretical study of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures

The electrical properties, optical properties and stabilities of hybrid lead iodide perovskite homologous semiconductors with 0D, 1D, 2D and 3D structures have been investigated based on their electronic structures calculated by density functional theory (DFT). The results indicated that the power conversion efficiencies (PCEs) estimated according to the absorption spectra of 1D perovskite homologues (1.9–10.9%) and 2D perovskite homologues (4.4–6.9%) are similar. However, the charge transport properties of 1D perovskite homologues (only ∼0% of that of the reference, CH3NH3PbI3) are entirely different from those of 2D perovskite homologues (reaching 43% of that of the reference) when a polycrystalline model has been introduced, although both of them are anisotropic materials. More charge transport paths of 2D perovskite homologues have been found in the polycrystalline state, compared with those of 1D perovskite homologues. Our findings have a great realistic significance to understand the properties of polycrystalline perovskite homologues.

Direct Observation of the Symmetrical and Asymmetrical Protonation States in Molecular Crystals

The symmetrical and asymmetrical protonation states are realized via the formation of intermolecular hydrogen bonds inside 9,10-bis((E)-2-(pyridin-4-yl)vinyl)anthracene (BP4VA) molecular crystals. With the protonation of H2SO4, BP4VA molecules are protonated symmetrically, while the molecules are asymmetrically protonated by introducing HCl. The different protonation states of BP4VA crystals result in various supramolecular interactions, aggregation states, and even tunable optical properties. It provides a fundamental principle to understand the effect of protonation in organic conjugated molecules and an approach to expanding the scope of organic functional materials.

Synthesis and properties of novel polymers based on PD electron-withdrawing unit

In this article, we designed and synthesized a series of 5-(2,6-dimethyl-4H-pyran-4-ylidene)-1,3-diethyl-2-thioxodihydropyrimidine- 4,6(1H, 5H)-dione (PD) unit based polymers (PFTDT, CZTDT, PHTDT and THTDT) for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability (all above 377 °C). Very broad absorption spectrum was also obtained from the polymer THTDT (300–850 nm). CV characterization found that these polymers owned low highest occupied molecular orbital (HOMO) energy levels (–5.39 eV for THTDT,–5.49 eV for CZTDT and–5.78 eV for PFTDT) except for PHTDT (–5.17 eV). The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.