纳米棒
载流子
材料科学
异质结
光激发
光电子学
半导体
超快激光光谱学
纳米技术
激发
光学
激光器
量子力学
物理
作者
Tanmay Goswami,Himanshu Bhatt,Dharmendra Kumar Yadav,Ramchandra Saha,K. Justice Babu,H. Ghosh
摘要
Efficient utilization of hot charge carriers is of utmost benefit for a semiconductor-based optoelectronic device. Herein, a one-dimensional (1D)/two-dimensional (2D) heterojunction was fabricated in the form of CdS/MoS2 nanorod/nanosheet composite and migration of hot charge carriers was being investigated with the help of transient absorption (TA) spectroscopy. The band alignment was such that both the electrons and holes in the CdS region tend to migrate into the MoS2 region following photoexcitation. The composite system is composed of optical signatures of both CdS and MoS2, with the dominance of CdS nanorods. In addition, the TA signal of MoS2 is substantially enhanced in the heterosystem at the cost of the diminished CdS signal, confirming the migration of charge carrier population from CdS to MoS2. This migration phenomenon was dominated by the hot carrier transfer. The hot carriers in the high energy states of CdS are preferentially migrated into the MoS2 states rather than being cooled to the band edge. The hot carrier transfer time for a 400 nm pump excitation was calculated to be 0.21 ps. This is much faster than the band edge electron transfer process, occurring at 2.0 ps time scale. We found that these migration processes are very much dependent on the applied pump photon energy. Higher energy pump photons are more efficient in the hot carrier transfer process and place these hot carriers in the higher energy states of MoS2, further extending charge carrier separation. This detailed spectroscopic investigation would help in the fabrication of better 1D/2D heterojunctions and advance the optoelectronic field.
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