How to Interpret Transient Absorption Data?: An Overview of Case Studies for Application to Organic Solar Cells

Abstract

Transient absorption spectroscopy (TAS) is a time‐resolved spectroscopic technique that can quantitatively observe temporal changes in the absorption spectrum associated with transient species, such as excitons and charges. Therefore, it is extensively used in photophysics, photochemistry, and photobiology. TAS plays a crucial role in unveiling charge generation and recombination dynamics in organic solar cells (OSCs). However, the interpretation of TA data is sometimes difficult for those who are not familiar with TAS. In this Perspective, therefore, the utility of TAS is briefly explained in studying OSCs and highlight key considerations for interpreting TA data. Measuring TA data at appropriate excitation fluence and appropriate spectral assignment are essential to correctly interpret photophysics of OSCs. With this Perspective, it aims to offer readers sufficient advice to enable them to perform TA measurements appropriately and interpret the TA data correctly.

Morphology Control Realizes Fast Charge Dissociation and Transport in High-Performance All-Polymer Solar Cells

“…The shorter τ 1 and τ 2 values indicate a faster diffusion rate of excitons toward the interface before dissociation and a more rapid exciton dissociation at the D/A interface. These findings illustrate that the treatment of DIO accelerates the hole transfer kinetics, boosting the photogenerated current and thereby enhancing the photovoltaic performance of the all-PSCs. ,− …”

Over 17.1% or 18.2% Efficiency of Layer-by-Layer All-Polymer Solar Cells via Incorporating Efficient Pt Complexes as Energy Donor Additive

“…TA spectra consist of two main features: negative signature originating from ground state bleach (GSB) and stimulated emission (SE), and positive signature originating from excited state absorption (ESA). 41 The TA spectra of neat PM6 and PM6:F-Pt films show an obvious GSB peak at about 620 nm, which can reflect the excited state decay dynamics of PM6. The decay dynamics of the GSB peak at 620 nm is fitted and shown in Figure 3c.…”

“…The transient absorption (TA) spectra of PM6, PM6:F-Pt, PY-IT as well as PY-IT:F-Pt films were measured under 400 nm light excitation and are shown in Figure . TA spectra consist of two main features: negative signature originating from ground state bleach (GSB) and stimulated emission (SE), and positive signature originating from excited state absorption (ESA) . The TA spectra of neat PM6 and PM6:F-Pt films show an obvious GSB peak at about 620 nm, which can reflect the excited state decay dynamics of PM6.…”

Brominated Quaternary Ammonium Salt-Assisted Hybrid Electron Transport Layer for High-Performance Conventional Organic Solar Cells

“…Organic solar cells (OSCs) have garnered considerable attention due to their merits including being flexible, lightweight, and solution-processable for manufacturing. − Recently, the maximum power conversion efficiency (PCE) of single-junction OSCs has approached nearly 20%, which is attributed to the emergence of nonfullerene photovoltaic materials together with the continuous optimization of device engineering. − A typical OSC is structured by two electrodes sandwiching a photoactive layer with hole (HTL) and electron (ETL) transport layers between their interfaces, in which the photoactive layer determines light-harvesting and free-carrier production, while the HTL/ETL play a vital role in carrier transport and long-term operational stability. − …”