Hot-electron transfer in quantum-dot heterojunction films

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.

Coherent Exciton Dynamics in Ensembles of Size-Dispersed CdSe Quantum Dot Dimers Probed via Ultrafast Spectroscopy: A Quantum Computational Study

“…Colloidal nanometric metallic and semi conducting quantum dots (QDs) have long been used as versatile building blocks for assembling dimers and larger extended arrays [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Among possible building blocks, isolated CdSe QDs were extensively studied [15][16][17][18][19].…”

“…Among possible building blocks, isolated CdSe QDs were extensively studied [15][16][17][18][19]. Driven by the possible applications to lasing, sensing, light harvesting, and information processing, they have recently received renewed attention focusing on understanding the role of the fine structure coupling [20][21][22][23][24], electronic and vibrational coherences [25][26][27][28][29][30][31][32] and coupling to biexcitons [30,[33][34][35][36][37], electron transport in arrays [38][39][40][41], and the possibility of engineering ultrafast energy transfer between a donor and an acceptor dot [10,11].…”

Atomic Layer Deposition of ZnO on InP Quantum Dot Films for Charge Separation, Stabilization, and Solar Cell Formation

“…If a QD film is infilled with a semiconductor material that is characterized by a type II band offset with the QDs, as shown schematically in Figure , then the resulting heterostructure can induce a separation between the two carriers (electrons and holes) while improving the film stability by blocking the diffusion of ambient oxidants to the QDs. If the band offsets are engineered to the correct energy levels it could also be possible to use this band alignment engineering scheme to enhance carrier multiplication (CM)—a process that creates multiple free electrons from one high‐energy photon . It was recently shown that the use of heterojunctions provides a systematic way to reduce the threshold energy for CM .…”

Photoinduced electron transfer in novel CdSe–Cu2Se type II core–shell quantum dots

“…[30][31][32][33] Many research groups have used the method of monitoring the luminescence of core-shell QDs in presences of an electron donor/ acceptor to investigate their charge carrier dynamics. 34,35 Zhang et al investigated the quenching of QD photoluminescence in the presence of hole acceptors and explored the static and dynamic factors involved. 36 A similar study in core-shell nanorods by Jiang group differentiated the quenching mechanism based on the nature of binding sites.…”