Zhijian Chen

Functional organogels from highly efficient organogelator based on perylene bisimide semiconductor

A new n-type semiconducting perylene bisimide dye has been synthesized that gelates a broad variety of organic solvents to afford well-defined nano- and mesoscopic helical fibers and bundles.

Tracing Single Electrons in a Disordered Polymer Film at Room Temperature

The transport of charges lies at the heart of essentially all modern (opto-) electronic devices. Although inorganic semiconductors built the basis for current technologies, organic materials have become increasingly important in recent years. However, organic matter is often highly disordered, which directly impacts the charge carrier dynamics. To understand and optimize device performance, detailed knowledge of the transport mechanisms of charge carriers in disordered matter is therefore of crucial importance. Here we report on the observation of the motion of single electrons within a disordered polymer film at room temperature, using single organic chromophores as probe molecules. The migration of a single electron gives rise to a varying electric field in its vicinity, which is registered via a shift of the emission spectra (Stark shift) of a chromophore. The spectral shifts allow us to determine the electron mobility and reveal for each nanoenvironment a distinct number of different possible electron-transfer pathways within the rugged energy landscape of the disordered polymer matrix.

Performance enhancement of perovskite solar cells by employing TiO2 nanorod arrays decorated with CuInS2 quantum dots

In this work, TiO2 nanorod arrays (TiO2-NAs) were modified by CuInS2 quantum dots (CuInS2 QDs) on the surface of the nanorods. The resultant TiO2-CuInS2 nanorod arrays (TiO2-CuInS2-NAs) were characterized by UV/Vis spectroscopy, transmission electronic microscopy (TEM), and X-ray diffraction (XRD). The TiO2-CuInS2-NAs were applied as scaffold for the preparation of organic-inorganic hybrid perovskite solar cells. In comparison with the solar cell devices based on TIO2-NAs, a significant improvement in the power conversion efficiency had been achieved and the highest efficiency was obtained as 11.7% (under 100 mW/cm2) through the optimization of the growth time of QDs on nanorods. The improvement of the device performance could be attributed to the assistance of CuInS2 QDs in the light harvesting as well as the facilitation of the electron injection from the perovskite to the TiO2 scaffold.

Coupled Cooperative Supramolecular Polymerization: A New Model Applied to the Competing Aggregation Pathways of an Amphiphilic aza-BODIPY Dye into Spherical and Rod-Like Aggregates

Based on our studies on biphasic self-assembly behavior of an amphiphilic BF2 -azadipyrromethene (aza-BODIPY) dye 1, a new analytical model to quantitatively describe the thermodynamic properties of the aggregation involving two competing supramolecular polymerization processes is proposed. In this model, the formation of the metastable as well as the thermodynamically stable aggregates was considered to follow a nucleated polymerization mechanism. The numerical calculation based on the new model gives insight into the formation of different species in such complicate aggregate systems. Moreover, the aggregation of the biphasic self-assembly processes for dye 1 was investigated by concentration-dependent UV/Vis spectroscopy. The experimental data were analyzed by using the new model to evaluate the thermodynamic parameters including aggregation constants, the size of nuclei, and the cooperativity the two types of aggregates.