Hot-electron transfer in quantum-dot heterojunction films
G. Grimaldi (TU Delft - ChemE/Opto-electronic Materials)
R.W. Crisp (TU Delft - ChemE/Opto-electronic Materials)
Stephanie Ten Brinck (Vrije Universiteit Amsterdam)
Felipe Zapata (Netherlands eScience Center, Vrije Universiteit Amsterdam)
M. van Ouwendorp (TU Delft - Applied Sciences)
N. Renaud (TU Delft - ChemE/Opto-electronic Materials)
Nicholas Kirkwood (TU Delft - ChemE/Opto-electronic Materials)
Wiel H. Evers (Kavli institute of nanoscience Delft, TU Delft - BN/Technici en Analisten)
Sachin Kinge (Toyota Motor Europe)
Ivan Infante (Vrije Universiteit Amsterdam)
Laurens Siebbeles (TU Delft - ChemE/Opto-electronic Materials)
A. J. Houtepen (TU Delft - ChemE/Opto-electronic Materials)
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Abstract
Thermalization losses limit the photon-to-power conversion of solar cells at the high-energy side of the solar spectrum, as electrons quickly lose their energy relaxing to the band edge. Hot-electron transfer could reduce these losses. Here, we demonstrate fast and efficient hot-electron transfer between lead selenide and cadmium selenide quantum dots assembled in a quantum-dot heterojunction solid. In this system, the energy structure of the absorber material and of the electron extracting material can be easily tuned via a variation of quantum-dot size, allowing us to tailor the energetics of the transfer process for device applications. The efficiency of the transfer process increases with excitation energy as a result of the more favorable competition between hot-electron transfer and electron cooling. The experimental picture is supported by time-domain density functional theory calculations, showing that electron density is transferred from lead selenide to cadmium selenide quantum dots on the sub-picosecond timescale.
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