Ultrafast Dynamics in between Alq₃ Molecules and Bulk Silicon

Yu Chan Tai^1*, Wen Yen Tzeng¹, Jhen Dong Lin¹, Ming Yang Huang¹, Shun Jen Cheng¹, Chun Liang Lin¹, Chih Wei Luo¹

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Yu Chan Tai, email:brianyjtai1994@gmail.com

Energy dynamics of quasiparticles in between adsorbates and substrates is an issue for the development of energy-conversion devices. In this study, the ultrafast dynamics of quasiparticles in organic tris-(8-hydroxyquinoline) aluminum (Alq₃) molecules were revealed by optical-pump optical-probe spectroscopy. We successfully observed an enhanced decay rate in time-resolved differential reflectivity of bulk silicon under the existence of Alq₃ photoluminescence excited by ultrashort laser pulses. Additionally, the decay rate of quasiparticles in Si substrates was significantly enhanced by the existence of Alq₃ molecules on the surface of Si. This result is confirmed by comparing two different time-resolved differential reflectivities of Alq₃ molecules deposited on copper and sapphire substrates. Comparing with the results of Alq₃ molecules on copper and sapphire substrates, we found that a relatively persistent electric field could accelerate the recombination process of Si from Alq₃ molecules, which is caused by the energy transfer between Alq₃ molecules and Si.

Keywords: Alq₃ Molecules, Silicon, Ultrafast Dynamics