Charge carrier dynamics in CdTe/ZnTe core/shell nanocrystals for photovoltaic applications

• Published in: Journal of chemical sciences (Bangalore, India) Vol. 130; no. 10; pp. 1 - 6
• Main Authors: Maiti, Sourav, Anand, Pranav, Azlan, Farazuddin, Ghosh, Hirendra N
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.10.2018; Springer Nature B.V
• Subjects: Absorption spectra; Absorption spectroscopy; Augers; Bleaches; Cadmium tellurides; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Cooling; Current carriers; Dynamics; Electrons; Emission analysis; Emission spectra; Excitation spectra; Nanocrystals; Photovoltaic cells; Quantum dots; Regular Article; Solar cells; Spectrum analysis; Surface chemistry; Synthesis; Zinc tellurides; solar enery conversion; Quasi type II core shell; electron transfer; Ultrafast spectroscopy
• ISSN: 0974-3626; 0973-7103
• DOI: 10.1007/s12039-018-1544-y

CdTe/ZnTe type-II core/shell nanocrystals were synthesized and characterized by the red-shift in the UV-Vis absorption and emission spectra along with the increase in both emission quantum yield and lifetime. The charge carrier dynamics was investigated through ultrafast transient absorption spectroscopy revealing the excited state carrier distribution and the dynamics through which the carriers decay. Upon laser pulse excitation the transient absorption spectrum was characterized by a broad ground state bleach signal in the core/shell nanocrystals in accord with the absorption spectra. Slower electron cooling was found in the core/shell nanocrystals compared to the CdTe core due to the type-II band-alignment that decouples the electron from hole preventing Auger-assisted electron cooling process. The recombination was found to be much slower in the core/shell nanocrystals due to the better surface passivation provided by the ZnTe shell eliminating the surface trapping process. The low band-gap CdTe based nanocrystals with a charge separated state are a viable candidate for photovoltaic applications and finally, we have investigated the potentiality of the synthesized nanocrystals as sensitizers in quantum dot solar cells. Graphical Abstract The charge carrier dynamics in type-II CdTe/ZnTe nanocrystals was investigated through ultrafast transient absorption spectroscopy. The core/shell nanocrystals depicted slower electron cooling as well as slower recombination process resulting in superior photovoltaic performance compared to the CdTe core.