Speaker: Prof. Xiaogang Peng (Department of Chemistry, Zhejiang University)

Time:14:30-16:30pm,January 6, 2024 

Venue: N308, State Key Laboratory of Luminescent Materials and Devices,

Abstract：

Solution semiconductor nanocrystals (Colloidal semiconductor nanocrystals) are semiconductor single crystals synthesized and processed in solution, with dimensions in the range of 1-100 nm and monodisperse in size. This scale range is comparable to, or slightly larger than, the exciton size of general inorganic semiconductors, resulting in nanocrystals that exhibit unique excitonic semiconductor characteristics in their optoelectronic properties near room temperature. Strictly speaking, nanocrystals with dimensions smaller than the bulk-phase exciton size are also known as quantum dots, but semiconductor nanocrystals are sometimes directly equated with quantum dots in the literature. The excitons in inorganic semiconductor bulk-phase single crystals are electron-hole pairs bound together by Coulomb interactions, also known as Wanier excitons. In nanoscale semiconductor single crystals, electron-hole pairs generated by photoexcitation or electrical excitation form dynamic excitons (dynamic excitons), whose bonding originates mainly from the spatially confined domains provided by the crystal-ligand interface of the nanocrystals. The nature of this quasiparticle cannot be described only by the energy band structure of the corresponding bulk-phase semiconductor single crystal, nor does it have a one-to-one correspondence with the nature of the ground state of the nanocrystal. Two samples of semiconductor nanocrystals with indistinguishable ground-state properties such as size, morphology, composition, and even absorption spectra may have vastly different fluorescence quantum yields (e.g., 100% for one and 0 for the other). Therefore, just controlling the synthesized nanocrystals at the size and morphology level is not the fundamental goal of semiconductor nanocrystal synthesis chemistry. Instead, the synthetic control of excitonic behavior in order to realize the functionality of semiconductor nanocrystals (luminescent and photovoltaic materials) is now fundamental to synthetic chemistry.

Biography of Invited Speaker：  

Xiaogang Peng is a professor in the Department of Chemistry, Zhejiang University . Before his return to China, he was Assistant Professor (1999-2003), Associate Professor (2003-2005), Professor and Chair Professor (2005-2009) at the University of Arkansas, USA. Xiaogang Peng completed his undergraduate studies at Jilin University in 1987 and his Ph.D. in 1992. He was a postdoctoral fellow at the University of California, Berkeley, from 1994 to 1996, and an assistant researcher at the Laurentian National Laboratory of Berkeley from 1996 to 1999. Xiaogang Peng's research interests include the synthesis, properties and applications of solution nanocrystals, with a focus on solution semiconductor nanocrystals (quantum dots).