Ghada H. Ahmed,Jiakai Liu,Manas R. Parida,Banavoth Murali,Riya Bose,Noktan M. AlYami,Mohamed N. Hedhili,Wei Peng,Jun Pan,Tabot M. D. Besong,Osman M. Bakr,Omar F. Mohammed
Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.
A series of perylene diimide (PDI) derivatives, TPP-PDI , TPO-PDI , and TPS-PDI , are developed for nonfullerene polymer solar cells (NF-PSCs) by flaking three PDI skeletons around 3D central cores with different configurations and electronic states, such as triphenylphosphine (TPP), triphenylphosphine monoxide (TPO), and triphenylphosphine sulfide (TPS). These small-molecule acceptors have a “three-wing propeller” structure due to their similar backbones. By changing the electron density of phosphorus atoms through oxidation and sulfuration, the “folding-back” strength is decreased, resulting in a less twisted molecular conformation. The stronger electron-withdrawing ability of the oxygen atom affords TPO-PDI the least twisted conformation, which enhances the crystallinity of this complex. NF-PSCs based on PTTEA : TPO-PDI exhibit a high power conversion efficiency (PCE) of 8.65%. Ultimately, the joint “molecular lock” effect arising from O H⋅⋅⋅F and O H⋅⋅⋅OP supramolecular interactions is achieved by introducing 4,4′-biphenol as an additive, which successfully promotes fibril-like phase separation and blend morphology optimization to generate the highest PCE of 11.01%, which is currently the highest value recorded for NF-PSCs based on PDI acceptors.
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