Excited-State Relaxation Dynamics of 3-Vinylthiophene-Terminated Silicon Quantum Dots

Abstract

In theory, silicon quantum dots (SiQDs) emit enhanced photoluminescence with a size-tunable spectrum in the visible range. In practice, surface states originating from oxide defect structures or organic ligands are strongly involved in exciton relaxation dynamics because the amplitudes of hole and electron wave functions are nonzero at the SiQD surface. In this study, SiQDs with well-defined surface properties were obtained through a wet-chemistry procedure providing SiQDs with adjustable sizes and oxide-free, 3-vinylthiophene-terminated surfaces. The 3-vinylthiophene-terminated SiQDs have a crystalline spherical 2 nm core and were observed to exhibit blue photoluminescence (∼460 nm) with a quantum yield and lifetime of ca. 23% and 1.3 ns, respectively. The interplay between electronically excited molecular states and conduction band states was examined upon direct monitoring of photoexcited carrier dynamics with femtosecond transient absorption spectroscopy. The 3-vinylthiophene ligands were found to act...