Size and Temperature Dependence of Electron Transfer between CdSe Quantum Dots and a TiO2 Nanobelt

作者：Tafen De Nyago^*; Prezhdo Oleg V

来源：Journal of Physical Chemistry C, 2015, 119(10): 5639-5647.

DOI：10.1021/jp5110278

Understanding charge transfer reactions between quantum dots (QD) and metal oxides is fundamental for improving photocatalytic, photovoltaic, and electronic devices. The complexity of these processes makes it difficult to find an optimum QD size with rapid charge injection and low recombination. We combine time-domain density functional theory with nonadiabatic molecular dynamics to investigate the size and temperature dependence of the experimentally studied electron transfer and charge recombination at CdSe QD-TiO2 nanobelt (NB) interfaces. The electron injection rate shows strong dependence on the QD size, increasing for small QDs. The rate exhibits Arrhenius temperature dependence, with the activation energy of the order of millielectronvolts. The charge recombination process occurs due to coupling of the electronic subsystem to vibrational modes of the TiO2 NB. Inelastic electron-phonon scattering happens on a picosecond time scale, with strong dependence on the QD size. Our simulations demonstrate that the electron-hole recombination rate decreases significantly as the QD size increases, in excellent agreement with experiments. The temperature dependence of the charge recombination rates can be successfully modeled within the framework of the Marcus theory through optimization of the electronic coupling and the reorganization energy. Our simulations indicate that by varying the QD size, one can modulate the photoinduced charge separation and charge recombination, fundamental aspects of the design principles for high-efficiency devices.

• 出版日期2015-3-12