Ultrafast Dynamics of Charge Transfer and Photochemical Reactions in Solar Energy Conversion

Abstract

For decades, ultrafast time‐resolved spectroscopy has found its way into an increasing number of applications. It has become a vital technique to investigate energy conversion processes and charge transfer dynamics in optoelectronic systems such as solar cells and solar‐driven photocatalytic applications. The understanding of charge transfer and photochemical reactions can help optimize and improve the performance of relevant devices with solar energy conversion processes. Here, the fundamental principles of photochemical and photophysical processes in photoinduced reactions, in which the fundamental charge carrier dynamic processes include interfacial electron transfer, singlet excitons, triplet excitons, excitons fission, and recombination, are reviewed. Transient absorption (TA) spectroscopy techniques provide a good understanding of the energy/electron transfer processes. These processes, including excited state generation and interfacial energy/electron transfer, are dominate constituents of solar energy conversion applications, for example, dye‐sensitized solar cells and photocatalysis. An outlook for intrinsic electron/energy transfer dynamics via TA spectroscopic characterization is provided, establishing a foundation for the rational design of solar energy conversion devices.

Characterizing photocatalysts for water splitting: from atoms to bulk and from slow to ultrafast processes

“…Time-resolved luminescence spectroscopy, and pumpprobe spectroscopic techniques, i.e., transient absorption (TA) in the visible, ultraviolet and IR range, sometimes complemented by time-resolved Raman experiments and more exotic techniques such as THz and X-ray absorption, are the most common techniques employed to gain insight into changes of the systems subsequent to excitation, i.e., into relaxation, charge transfer and recombination processes and have been extensively reviewed. [129][130][131][132][133][134][135][136] Already observing the quenching of PL intensity and changes in the PL lifetime of a photosensitizer or semiconductor in the presence of a co-catalyst can give first indication on the presence and time scale of additional energy or charge transfer processes influencing the lifetime of the emitting state. While PL spectroscopy is only sensitive to bright states, TA spectroscopy can also probe non-emitting states because it is based on the observation of changes in the electronic transitions (UV/vis/NIR) and vibrational frequencies (IR) after excitation.…”

In situ charge carrier dynamics of semiconductor nanostructures for advanced photoelectrochemical and photocatalytic applications

“…Transient absorption (TA) spectroscopy is a powerful tool for examining the charge transfer events of semiconductor nanostructures [32,33]. Ex situ measurement is a common method for analyzing the charge dynamics properties of semiconductors by TA.…”

Atomic‐Level Charge Separation Strategies in Semiconductor‐Based Photocatalysts

“…The time‐resolved spectroscopy techniques, involving transient absorption spectroscopy (TAS), time‐resolved photoluminescence spectroscopy (TRPL) or time‐resolved fluorescence spectroscopy (TRFS) and transient surface photovoltage (TSPV) are used to probe the ultrafast carrier dynamics processes with the time features as short as fs. [ 61,62 ] TAS technology can be used to obtain the information of the ground and excited state, as well as the radiation recombination of photogenerated charge carriers. When the fraction of the excited electrons generated with the help of the pulse lasers, the weak probe pulse is sent through the sample with a time delay τ.…”