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The kinetic aggregation of nonfullerene acceptors under nonequilibrium conditions can induce electron–phonon interaction roll‐off and electronic band structure transition, which represents an important limitation for long‐term operational stability of organic solar cells (OSCs). However, the fundamental underlying mechanisms have received limited attention. Herein, a photophysical correlation picture between intermolecular electron–phonon coupling and trapping of electronic excitation is proposed based on the different aggregation behaviors of BTP‐eC9 in bulk‐heterojunction and layer‐by‐layer processed multicomponent OSCs. Two separate factors rationalize their correlation mechanisms: 1) the local lattice and/or molecular deformation can be regarded as the results of BTP‐eC9 aggregates in binary system under continuous heating, which brings about attenuated intermolecular electron–phonon coupling with intensified photocarrier trapping. 2) The higher density of trap states with more extended tails into the bandgap give rise to the formation of highly localized trapped polarons with a longer lifetime. The stabilized intermolecular electron–phonon coupling through synergistic regulation of donor and acceptor materials effectively suppresses unfavorable photocarrier trapping, delivering the improved device efficiency of 18.10% and enhanced thermal stability in quaternary OSCs. These results provide valuable property–function insights for further boosting photovoltaic stability in view of modulating intermolecular electron–phonon coupling.

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The self-trapping of a free carrier in transition-metal oxides can lead to a small polaron, which is responsible for the inadequate performance of the oxide-based optoelectronic applications. Thus, fundamental understanding of the self-trapping mechanism is of key importance for improving the performance of these applications. Herein, the self-trapping in Co 3 O 4 epitaxial monocrystalline films is investigated primarily by transient absorption spectroscopy. The spectral evolution corresponding to the ultrafast transition from free carriers to small polarons is identified, which allows us to extract the self-trapping kinetics. The relationship between the self-trapping rate and temperature suggests a lack of thermal activation energy. A barrierless self-trapping mechanism derived from the small polaron framework is then proposed, which can successfully describe the observation that self-trapping rate decreases linearly with increasing temperature. Given that small polarons are ubiquitous in transition-metal oxides, this self-trapping mechanism is potentially a general phenomenon in these materials.

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The antimony chalcogenide crystals are composed of quasi-one-dimensional [Sb4X6] n ribbons, which lead to strong anisotropic optical and electronic properties. An attempt to exploit photoconductivity anisotropy in the device fabrication may introduce a rewarding strategy to propel the development of the antimony chalcogenide solar cells. To achieve this, understanding of the dynamic evolution of the photoconductivity anisotropy is required. Here, the photoconductivities along different lattice directions in an antimony selenide single crystal are investigated by time-resolved terahertz spectroscopy. We find that electron trapping results in a variation of the photoconductivity anisotropy accompanied by a decrease in the photoconductivity magnitude, while electron–hole recombination only reduces the magnitude but does not affect the anisotropy. Therefore, measuring the temporal evolution of photoconductivity anisotropy can provide a wealth of information regarding the nature of the photocarrier and also render a probe to selectively evaluate the photoconductivity decay mechanisms.

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The photocarrier recombination in van der Waals layers may determine the device performance based on these materials. Here, we investigated the photocarrier dynamics in a multilayer indium selenide nanofilm using transient absorption spectroscopy. The sub-bandgap transient absorption feature was attributed to the indirect intraband absorption of the photocarriers, which was then exploited as a probe to monitor the photocarrier dynamics. With increasing pump intensities, the photocarrier decay was accelerated because of the rising contribution from a bimolecular recombination channel that was then assigned to the exciton-exciton annihilation. The rate constant of the exciton-exciton annihilation was given as (1.8 0.1) 10-15 cm2 ps-1 from a global fitting of the photocarrier decay kinetics for different pump intensities. Our finding suggests that, in contrast with their monolayer counterpart, the exciton-exciton annihilation is actually quite inefficient in multilayers due to the weaker Coulomb interaction. Hence, compared with the monolayers, the lifetime of photocarriers in multilayers would not be significantly reduced under high-intensity pump condition, and the apparent photocarrier lifetime could be further improved just by suppressing the monomolecular recombination channels such as trapping.