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arXiv · 2412.16371

Photocurrent Enhancement due to Spin-Exchange Carrier Multiplication in Films of Manganese-Doped 'Inverted' CdSe/HgSe Quantum Dots

Jungchul Noh·Clément Livache·Donghyo Hahm·Valerio Pinchetti·Ho Jin·Changjo Kim·Victor I. Klimov
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Abstract

Incorporation of manganese impurities into II-VI semiconductors results in a dramatic change in their properties due to strong exchange interactions between the Mn ion and the semiconductor host. In colloidal quantum dots (QDs), these interactions result in a rapid bidirectional energy transfer between the magnetic impurity and the QD intrinsic states, which is characterized by an extremely high energy transfer rate of more than ~5 eV/ps. This rate is higher than the rate of energy loss due to phonon emission (typically, ~1 eV/ps or less), so Mn-QD interactions could in principle be used to capture and utilize the kinetic energy of the hot carrier before it is lost to phonons. Here, we demonstrate that by using Mn-doped CdSe/HgSe core/shell QDs, we can efficiently convert the kinetic energy of a hot exciton into an additional electron-hole pair (exciton). This carrier multiplication process occurs through rapid capture of a hot exciton by a Mn ion, which then undergoes spin flip relaxation, producing two excitons near the QD band edge. Due to the inverted geometry of the CdSe/HgSe QDs, both electrons and holes resulting from carrier multiplication occupy the QD shell, allowing them to be easily extracted from the QD for potential use in electro-optical devices or chemical reactions.

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Jungchul Noh, Clément Livache, Donghyo Hahm, Valerio Pinchetti, Ho Jin, Changjo Kim, Victor I. Klimov. 2024-12-20. Photocurrent Enhancement due to Spin-Exchange Carrier Multiplication in Films of Manganese-Doped 'Inverted' CdSe/HgSe Quantum Dots. https://arxiv.org/abs/2412.16371

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