Public Abstract

DE-FG02-07ER46474: Hybrid interfaces between silicon and excitonic materials

Award Status: Active

Institution: Massachusetts Institute of Technology, Cambridge, MA
UEI: E2NYLCDML6V1
PM: Henderson, Craig

Most Recent Award Date: 07/23/2026
Number of Support Periods: 19
PI: Baldo, Marc

Current Budget Period: 07/01/2025 - 06/30/2027
Current Project Period: 07/01/2025 - 06/30/2027

Public Abstract

Hybrid interfaces between silicon and excitonic materials PI: Marc Baldo Massachusetts Institute of Technology Excitonic materials have highly localized excited states with strong optical transitions and potentially useful nonlinear effects. But they also exhibit correspondingly poor electronic transport and, in most applications, excitonic materials are more promising as partners than replacements for silicon in optoelectonic applications. Meanwhile, silicon has an indirect band gap, which means it requires a phonon to emit light and it struggles to absorb photons close to its bandgap. This project therefore addresses the poor optical properties of silicon by complementing it with excitonic materials such as molecules or quantum dots. Scientifically, however, the combination of silicon and excitonic materials has been long-neglected and remains poorly understood. One crucial goal is to realize energy transfer across the interface. But this requires charge tunneling that is incompatible with traditional, thick silicon passivation layers. Indeed, coupling silicon to exciton fission, a problem first proposed by Dexter in 1979, remained unsolved for 45 years¹. This research project studies Dexter’s archetype tetracene-silicon system. Rather than relying on Dexter transfer - simultaneous tunneling of electrons and holes, we demonstrate a new approach to hybrid interfaces, thinning the inorganic silicon passivation layer to ~ 1nm and introducing an interfacial excitonic layer designed to promote sequential charge tunneling. We observe a correspondingly successful transfer of triplet excited states to silicon, as measured by a photocurrent yield exceeding 100% for the first time in the visible spectrum. Building on this foundation, our primary goals is to establish the science of hybrid silicon-excitonic interfaces by characterizing and understanding their dynamics. In particular, we will implement new transient surface photovoltage experimental probes of charge transfer at the surface, and new materials to promote energy transfer as well as improving the passivation properties of the tunnel barrier. Successful demonstration of energy transfer at hybrid interfaces combining silicon and excitonic materials promises to form a new bridge between electronics and photonics. Understanding their materials and dynamics will improve the efficiency of energy transduction in applications spanning from solar cells to integrated photonics. 1. Dexter, D. L. Two Ideas On Energy-Transfer Phenomena - Ion-Pair Effects Involving The OH Stretching Mode, And Sensitization of Photo-Voltaic Cells. J. Lumines. 18-9, 779-784 (1979).

Hybrid interfaces between silicon and excitonic materials

PI: Marc Baldo

Massachusetts Institute of Technology

Excitonic materials have highly localized excited states with strong optical transitions and potentially useful nonlinear effects. But they also exhibit correspondingly poor electronic transport and, in most applications, excitonic materials are more promising as partners than replacements for silicon in optoelectonic applications. Meanwhile, silicon has an indirect band gap, which means it requires a phonon to emit light and it struggles to absorb photons close to its bandgap. This project therefore addresses the poor optical properties of silicon by complementing it with excitonic materials such as molecules or quantum dots.

Scientifically, however, the combination of silicon and excitonic materials has been long-neglected and remains poorly understood. One crucial goal is to realize energy transfer across the interface. But this requires charge tunneling that is incompatible with traditional, thick silicon passivation layers. Indeed, coupling silicon to exciton fission, a problem first proposed by Dexter in 1979, remained unsolved for 45 years¹.

This research project studies Dexter’s archetype tetracene-silicon system. Rather than relying on Dexter transfer - simultaneous tunneling of electrons and holes, we demonstrate a new approach to hybrid interfaces, thinning the inorganic silicon passivation layer to ~ 1nm and introducing an interfacial excitonic layer designed to promote sequential charge tunneling. We observe a correspondingly successful transfer of triplet excited states to silicon, as measured by a photocurrent yield exceeding 100% for the first time in the visible spectrum. Building on this foundation, our primary goals is to establish the science of hybrid silicon-excitonic interfaces by characterizing and understanding their dynamics. In particular, we will implement new transient surface photovoltage experimental probes of charge transfer at the surface, and new materials to promote energy transfer as well as improving the passivation properties of the tunnel barrier.

Successful demonstration of energy transfer at hybrid interfaces combining silicon and excitonic materials promises to form a new bridge between electronics and photonics. Understanding their materials and dynamics will improve the efficiency of energy transduction in applications spanning from solar cells to integrated photonics.

1. Dexter, D. L. Two Ideas On Energy-Transfer Phenomena - Ion-Pair Effects Involving The OH Stretching Mode, And Sensitization of Photo-Voltaic Cells. J. Lumines. 18-9, 779-784 (1979).