Cao, W.Yuan, L.Patterson, R.Wen, X.Tapping, P.Kee, T.Veetil, B.Zhang, P.Zhang, Z.Zhang, Q.Reece, P.Bremner, S.Shrestha, S.Conibeer, G.Huang, S.2018-11-062018-11-062017Nanoscale, 2017; 9(43):17133-171422040-33642040-3372http://hdl.handle.net/2440/115802Published on 29 September 2017The carrier dynamics of lead sulphide quantum dot (PbS QD) drop cast films and closely packed ordered Langmuir-Blodgett films are studied with ultra-fast femtosecond transient absorption spectroscopy. The photo-induced carrier temperature is extracted from transient absorption spectra and monitored as a function of time delay. The cooling dynamics of carriers in PbS QDs suggest a reduction of the carrier energy loss rate at longer time delays through the retardation of the longitudinal optical (LO) phonon decay due to partial heating of acoustic phonon modes. A slowed hot carrier cooling time up to 116 ps is observed in the drop cast film. A faster cooling rate was also observed in the highly compact Langmuir-Blodgett film due to the enhanced carrier-LO phonon coupling strength arising from the Coulombic interaction in neighboring QDs, which is verified by temperature dependent steady state PL measurements.enThis journal is © The Royal Society of Chemistry 2017Journal article003007718110.1039/c7nr05247b0004149609000682-s2.0-85033800608386961Tapping, P. [0000-0002-2359-1304]Kee, T. [0000-0002-4907-4663]