Trinh M Tuan, Houtepen Arjan J, Schins Juleon M, Hanrath Tobias, Piris Jorge, Knulst Walter, Goossens Albert P L M, Siebbeles Laurens D A
Optoelectronic Materials, Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands.
Nano Lett. 2008 Jun;8(6):1713-8. doi: 10.1021/nl0807225. Epub 2008 May 20.
Efficient carrier multiplication has been reported for several semiconductor nanocrystals: PbSe, PbS, PbTe, CdSe, InAs, and Si. Some of these reports have been challenged by studies claiming that carrier multiplication does not occur in CdSe, CdTe, and InAs nanocrystals, thus raising legitimate doubts concerning the occurrence of carrier multiplication in the remaining materials. Here, conclusive evidence is given for its occurrence in PbSe nanocrystals using femtosecond transient photobleaching. In addition, it is shown that a correct determination of carrier-multiplication efficiency requires spectral integration over the photobleach feature. The carrier multiplication efficiency we obtain is significantly lower than what has been reported previously, and it remains an open question whether it is higher in nanocrystals than it is in bulk semiconductors.
据报道，几种半导体纳米晶体（PbSe、PbS、PbTe、CdSe、InAs和Si）中存在高效的载流子倍增现象。其中一些报道受到了质疑，有研究称CdSe、CdTe和InAs纳米晶体中不存在载流子倍增现象，这使得人们对其他材料中载流子倍增现象的发生产生了合理怀疑。在此，利用飞秒瞬态光漂白给出了PbSe纳米晶体中载流子倍增现象发生的确凿证据。此外，研究表明，正确测定载流子倍增效率需要对光漂白特征进行光谱积分。我们获得的载流子倍增效率明显低于先前报道的值，纳米晶体中的载流子倍增效率是否高于体相半导体仍是一个悬而未决的问题。
