Hot carrier extraction from 2D semiconductor photoelectrodes

TL;DR

This study demonstrates ultrafast hot carrier extraction from monolayer MoS2 in a proof-of-concept solar cell, revealing new pathways for efficient, ultrathin photovoltaic devices using 2D semiconductors.

Contribution

It introduces a novel combination of spectroscopic techniques to achieve ultrafast hot carrier extraction in 2D MoS2-based photoelectrochemical cells, enabling potential cost-effective solar energy applications.

Findings

Ultrafast (<50 fs) hot exciton and free carrier extraction achieved.

Efficient charge transport over 1 cm^2 area with 7 Å thickness.

Theoretical insights into exciton state distribution and electronic coupling.

Abstract

Hot carrier-based energy conversion systems could double the efficiency of conventional solar energy technology or drive photochemical reactions that would not be possible using fully thermalized, ``cool'' carriers, but current strategies require expensive multi-junction architectures. Using an unprecedented combination of photoelectrochemical and in situ transient absorption spectroscopy measurements, we demonstrate ultrafast (<50 fs) hot exciton and free carrier extraction under applied bias in a proof-of-concept photoelectrochemical solar cell made from earth-abundant and potentially inexpensive monolayer (ML) MoS2. Our approach facilitates ultrathin 7\AA charge transport distances over 1 cm^2 areas by intimately coupling ML-MoS2 to an electron-selective solid contact and a hole-selective electrolyte contact. Our theoretical investigations of the spatial distribution of exciton states suggest greater electronic coupling between hot exciton states located on peripheral S atoms and neighboring contacts likely facilitates ultrafast charge transfer. Our work delineates future 2D semiconductor design strategies for practical implementation in ultrathin photovoltaic and solar fuels applications.