Induced UV photon sensing properties in narrow bandgap CdTe quantum dots through controlling hot electron dynamics

Thankappan Thrupthika; Devaraj Nataraj; Subramaniam Ramya; Arumugam Sangeetha; T Daniel Thangadurai

doi:10.1039/d3cp02424e

Induced UV photon sensing properties in narrow bandgap CdTe quantum dots through controlling hot electron dynamics

Phys Chem Chem Phys. 2023 Sep 27;25(37):25331-25343. doi: 10.1039/d3cp02424e.

Authors

Thankappan Thrupthika¹, Devaraj Nataraj^{1

2}, Subramaniam Ramya¹, Arumugam Sangeetha¹, T Daniel Thangadurai³

Affiliations

¹ Quantum Materials & Devices Laboratory, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu 641 046, India. de.nataraj@buc.edu.in.
² UGC-CPEPA Centre for Advanced Studies in Physics for the Development of Solar Energy Materials and Devices, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, 641 046, India.
³ KPR Institute of Engineering and Technology, Coimbatore, Tamil Nadu, 641 407, India. danielthangadurai.t@kpriet.ac.in.

PMID: 37702661
DOI: 10.1039/d3cp02424e

Abstract

Mn-doped CdTe (Mn-CdTe) quantum dot (QD) as well as quantum dot solid (QD solid) nanostructures are formed and the established structures are confirmed through HR-TEM analysis. The dynamics of charge carriers in both doped & undoped QD and QD solid structures were investigated by transient absorption (TA) spectroscopy. A slow band edge bleach recovery is obtained for Mn-doped CdTe QD and CdTe QD solid systems at room temperature. Additionally, a blue shifted broad bleach behaviour is identified for the Mn-CdTe QD solid system, which is attributed to hot exciton formation in the solid upon photoexcitation with a higher photon energy than the band gap energy (hν > E_g). This noteworthy process of generation of hot excitons and slow charge recombination occurs by means of a synergetic action of the Mn dopant in the host CdTe QD solid system as well as the extended electronic wave function between the coupled QD solid. Apart from the Mn-assisted delayed relaxation of hot electrons in the QD solid, a suppression in dark current as well as a high I_ON/I_OFF ratio of 3203.12 at 1 V is observed in the Mn-CdTe QD-solid based photosensitized device in the visible region. Furthermore, we were able to improve the UV photon harvesting property in a narrow band gap Mn-CdTe QD solid through reducing the higher excited carrier's energy losses.