Verma Sandeep, Ghosh Hirendra N
Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
Phys Chem Chem Phys. 2017 Sep 20;19(36):24896-24902. doi: 10.1039/c7cp04069e.
Semiconductor heterostructures with type-II band alignment are well known for their engineering property of efficient charge separation in photogenerated carriers. Herein, type-II CdSe/ZnO core/shell quantum dot heterostructures with CdSe shells of different thicknesses have been synthesized and a study of carrier dynamics is carried out using femtosecond transient absorption and picosecond emission spectroscopy. Carrier lifetime measurements by transient emission spectroscopy have revealed reduced electron-hole overlap in the type-II localization regime of ZnO/CdSe heterostructures. Femtosecond transient absorption studies have revealed hot electron transfer from CdSe shell to ZnO core prior to electron cooling in the CdSe shell. In addition, a surface channel for the hole cooling process has been identified in the transient absorption measurements. Effects of carrier trapping at interfacial defect states and type-II localization on carrier recombination have been recognized in our transient absorption and emission studies of ZnO/CdSe QDs heterostructure.
具有II型能带排列的半导体异质结构因其在光生载流子中有效电荷分离的工程特性而广为人知。在此，合成了具有不同厚度CdSe壳层的II型CdSe/ZnO核壳量子点异质结构，并使用飞秒瞬态吸收和皮秒发射光谱对载流子动力学进行了研究。通过瞬态发射光谱进行的载流子寿命测量表明，在ZnO/CdSe异质结构的II型定位区域中，电子-空穴重叠减少。飞秒瞬态吸收研究表明，在CdSe壳层中的电子冷却之前，热电子从CdSe壳层转移到ZnO核。此外，在瞬态吸收测量中确定了空穴冷却过程的表面通道。在我们对ZnO/CdSe量子点异质结构的瞬态吸收和发射研究中，已经认识到界面缺陷态处的载流子俘获和II型定位对载流子复合的影响。
