It is highly desirable, while still challenging, to obtain noble metal nanocrystals with custom capping ligands, because their colloidal synthesis relies on specific capping ligands for the shape control while conventional ligand exchange processes suffer from "the strong replaces the weak" limitation, which greatly hinders their applications. Herein, we report a general and effective ligand exchange approach that can replace the native capping ligands of noble metal nanocrystals with virtually any type of ligands, producing flexibly tailored surface properties. The key is to use diethylamine with conveniently switchable binding affinity to the metal surface as an intermediate ligand. As a strong ligand, it in its original form can effectively remove the native ligands; while protonated, it loses its binding affinity and facilitates the adsorption of new ligands, especially weak ones, onto the metal surface. By this means, the irreversible order in the conventional ligand exchange processes could be overcome. The efficacy of the strategy is demonstrated by mutual exchange of the capping ligands among cetyltrimethylammonium, citrate, polyvinylpyrrolidone, and oleylamine. This novel strategy significantly expands our ability to manipulate the surface property of noble metal nanocrystals and extends their applicability to a wide range of fields, particularly biomedical applications.

Polymer–polymer blends have been reported to exhibit exceptional thermal and ambient stability. However, power conversion efficiencies (PCEs) from devices using polymeric acceptors have been recorded to be significantly lower than those based on conjugated molecular acceptors. Herein, two organic nonfullerene bulk heterojunction (BHJ) blends ITIC:PBDB-T and N2200:PBDB-T, together with their fullerene counterpart, PCBM:PBDB-T, are adopted to understand the effect of electron acceptors on device performance. Free charge carrier properties using time-resolved microwave conductivity (TRMC) measurements are comprehensively investigated. The nonfullerene devices show an improved PCE of 10.06% and 6.65% in the ITIC- and N2200-based cells, respectively. In comparison, the PCBM:PBDB-T-based devices yield a PCE of 5.88%. The optimal N2200:PBDB-T produced the highest TRMC mobility, longest lifetime, and greatest free-carrier diffusion length. It is found that such phenomena can be associated with the unfavorable morphology of the all-polymer BHJ microstructure. In contrast, the solar cells using either the PCBM or ITIC acceptors display a more balanced donor and acceptor phase separation, leading to more efficient free-carrier separation and transport in the operating device. By sacrificing efficiency for superior stability, it is shown that the improved structure in all-polymer blend can deliver a more stable morphology under thermal stress.

A deep understanding of the dynamics of photogenerated charge carriers is extremely important for promoting their germination in semiconductors to enhance the efficiency of solar energy conversion. In contrast to that of organic molecular heterojunctions (which are widely employed in organic solar cells), the charge transfer dynamics of purely inorganic molecular heterojunctions remains unexplored. Herein, we reveal the dynamics of charge transfer between inorganic semiconductor molecular heteroclusters by selecting a group of open-framework metal chalcogenides as unique structure models constructed from supertetrahedral T3-InS ([In₁₀S₂₀]) and T4-MInS ([M₄In₁₆S₃₅], M = Mn or Fe) clusters. The staggered band gap alignment in T3-T4-MInS molecular heterojunctions enables the photogenerated charge carriers to be directionally transferred from T3-InS clusters to adjacent T4-MInS clusters upon irradiation or application of an external electric field. The simultaneous independence of and interactions between such two heteroclusters are investigated by theoretical calculations, steady- and transient-state absorption/photoluminescence spectroscopy, and surface photovoltage analysis. Moreover, the dynamics of cluster-to-cluster-to-dopant photogenerated charge transfer is deliberately elucidated. Thus, this work demonstrates the direct observation of charge transfer between molecular heterojunctions based on purely inorganic semiconductor clusters and is expected to promote the development of cluster-based semiconductors for solar cells.