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Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO2 brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO2 NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO2 NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties. [ABSTRACT FROM AUTHOR]

PEG-SH-capped gold nanorods (Au NRs)well dispersed in variousorganic solvents have been prepared to study the solvent effects onthe two-photon photoluminescence (TPPL) properties and ultrafast excitationdynamics of Au NRs. The TPPL intensities of Au NRs in different organicsolvents including DMF, DEG, CH3OH, C2H5OH, CH3CN, DMSO, and THF were found to be significantlyquenched compared to that of Au NRs in H2O. Ultrafast time-resolvedtransient absorption and pump–probe measurements have beenperformed on Au NRs in H2O, DMF, and DEG to understandthe corresponding quenching mechanisms. Different from the excitationdecay behaviors of Au NRs in H2O, an additional transientspecies was observed in Au NRs in DMF or DEG upon photoexcitation.This intermediate state is ascribed to the charge-separated species,which serves as direct evidence to support that the observed TPPLquenching in various organic solvents is due to electron transferfrom electron-donating solvents to the excited Au NRs. The charge-transfermechanism was further supported by the observation that the TPPL intensityof Au NRs in H2O was found to be quenched by nearly 5.0-foldin the presence of S2–. These studies provide usefulinformation on fundamental understanding of the TPPL properties aswell as development of various potential biological applications ofgold nanoparticles. [ABSTRACT FROM AUTHOR]

Due to their relatively high compatibility with specific photonic structures, strong light-matter interactions and unique nonlinear optical response, two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, are attractive for ultrafast photonics applications. Here, we fabricate MoS2/graphene nanocomposites by a typical hydrothermal method. In addition, we systematically investigate their nonlinear optical responses. Our experiments indicate that the combined advantages of ultrafast relaxation, a broadband response from graphene, and the strong light-matter interaction from MoS2, can be integrated together by composition. The optical properties in terms of carrier relaxation dynamics, saturation intensity and modulation depth suggest great potential for the MoS2/graphene nanocomposites in photonics applications. We have further fabricated 2D nanocomposites based optical saturable absorbers and integrated them into a 1.5 μm Erbium-doped fiber laser to demonstrate Q-switched and mode-locked pulse generation. The fabrication of 2D nanocomposites assembled from different types of 2D materials, via this simple and scalable growth approach, paves the way for the formation and tuning of new 2D materials with desirable photonic properties and applications. [ABSTRACT FROM AUTHOR]