Ultrafast Dynamics of Multiple Exciton Harvesting in the CdSe-ZnO System: Electron Injection versus Auger Recombination

作者：Zidek Karel^*; Zheng Kaibo; Abdellah Mohamed; Lenngren Nils; Chabera Pavel; Pullerits Tonu

来源：Nano Letters, 2012, 12(12): 6393-6399.

DOI：10.1021/nl303746d

• Quantum dots
• solar cell
• electron transport
• ultrafast transient absorption
• multiple exciton generation

We study multiple electron transfer from a CdSe quantum dot (QD) to ZnO, which is a prerequisite for successful utilization of multiple exciton generation for photovoltaics. By using ultrafast time-resolved spectroscopy we observe competition between electron injection into ZnO and quenching of multiexcitons via Auger recombination. We show that fast electron injection dominates over biexcitonic Auger recombination and multiple electrons can be transferred into ZnO. A kinetic component with time constant of a few tens of picoseconds was identified as the competition between injection of the second electron from a doubly excited QD and a trion Auger recombination. Moreover, we demonstrate that the multiexciton harvesting efficiency changes significantly with QD size. Within a narrow QD diameter range from 2 to 4 nm, the efficiency of electron injection from a doubly excited QD can vary from 30% to 70% in our system.

• 出版日期2012-12