Organic diboron compounds are well-known reagents for organic synthesis. They are widely employed in Suzuki coupling and Miyaura borylation reactions. By contrast, the use of them in inorganic materials chemistry is much less known. The researchers in the College of Engineering, Peking University have developed an application of diboron compounds in energy conversion materials and devices.
Semiconducting oxides such as TiO2, ZnO, and SnO2 are well-known materials in the fields of energy conversion, photocatalysis, and environmental protection, but their main disadvantage comes from a wide band gap that limits the utility of visible light energy.
Researchers have devoted time to expanding the energy absorption region into visible light, near infrared and microwave ranges. Based on the work of others, Prof. Fanyang Mo of College of Engineering developed a new semiconductor oxide modification method and obtained a series of impressive results.
“This proposal was based on the bonding interaction between the semiconductor oxide surface and the diboron compound, whereby the latter coordinates to the surface bridging O2c oxygen atoms and -OH groups. The surface-bound complex can rearrange the surface electronic structure and induce absorption of visible light,” said Prof. Mo.
Fig.1 Scheme diagram of the Ti3+ on the surface of TiO2
Additionally, the researchers have tried to gain a deeper insight into the interaction between the diboron compound and TiO2, and found out that novel surface states were established, and the device applying the surface states exhibited highly enhanced optoelectronic performance.
The paper was published in the latest issue of iScience (Modification of TiO2 Nanoparticles with Organodiboron Molecules Inducing Stable Surface Ti3+ Complex, iScience 2019, 20, 195-204)
Fig. 2 Schematic diagram of the diboron-modified photodetector with enhanced efficiency
The authors also studied the interaction between ZnO nanoparticles and diboron compounds and discovered the dual-spin surface state of ZnO (see Fig.3). The results are published in a recent issue of Langmuir (Zn+-O- dual-spin surface states formation by modification of ZnO nanoparticles with diboron compounds, Langmuir, 2019, 35, acs.langmuir.9b01955).
Fig.3 Dual-spin states on the surface of ZnO materials modified with diboron molecules
The interface engineering strategy with diboron compounds was further applied in the planar perovskite solar cell employing SnO2 as ETL. Prof. Fanyang Mo and Prof. Huanping Zhou (also in the College of Engineering) found that the device showed enhanced performance. The work was published in Solar RRL (Sol. RRL 2019, 3, 201900217) recently (Fig.4).
Fig. 4. The performance up level of the solar cell device.
Additionally, Prof. Rui Zhu of Peking University introduced diboron compounds into the preparation of perovskite solar cells, and found that the molecule could reduce the defects in a solar cell’s perovskite layer by removing redundant I ion species, and the solar cell performance was significantly improved (Fig. 5). The work was published in Adv. Mater (Adv. Mater. 2018, 1805085).
Fig. 5. Schematic diagram for the diboron compound’s defect control strategy
To summarize, researchers from Peking University found a new way to tune the surface electronic structure of semiconductor oxides by using organic diboron compounds. This interdisciplinary study by integrating diboron compounds with semiconductor oxides’ surface states and band structure delivered a series of important findings. These findings introduce new insights into topological states and energy-related interface structures, with potential applications in catalysis. The results provide a new approach to adjusting the surface electronic band structure and spin states.
Those who are interested in the work above or would like to collaborate are welcome to contact Prof. Mo. (email@example.com).
The research group greatly appreciate the kind instructions from Prof. Wanhong Ma of the Institute of Chemistry, Chinese Academy of Sciences (CAS).