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Spiro‐OMeTAD is one of the most used hole transport layers (HTLs) in high efficiency n‐i‐p perovskite solar cells (PSCs). However, due to the unsatisfactory conductivity of pristine Spiro‐OMeTAD, additives such as tert‐butylpyridine (tBP) and lithium bis (trifluoromethylsulfonyl)‐imide (LiTFSI) are required to improve its hole transportation. The hygroscopic nature of these additives inevitably deteriorates the device's stability. Here, it is shown that by adding fluorinated graphene (FG) into the Li‐TFSI and tBP doped Spiro‐OMeTAD, both efficiency and stability of the PSCs are significantly enhanced. Using the FG incorporated Spiro‐OMeTAD HTL, the power conversion efficiency (PCE) of the PSC reaches 21.92%, which is 11.8% higher than the original device. The FG not only improves the hole mobility of Spiro‐OMeTAD but also effectively reduces the amount of lithium ions in the perovskite layer and improves the hydrophobicity of the HTL. The FG incorporating cell shows better stability, maintaining 90% of initial efficiency over a 2400 h test in ambient conditions with 25% humidity. Finally, it is further demonstrated that the valence band of FG incorporated Spiro‐OMeTAD HTL has a positive effect on PSCs with a 2D interfacial layer, achieving an impressive PCE of 23.14% and a Voc of 1.226 V. [ABSTRACT FROM AUTHOR]

In this paper, new strategies are proposed to design high‐performance organic–inorganic hybrid perovskite (PVK)‐based triboelectric nanogenerators (TENGs) via both chemical composition modulation and electric field‐induced ion migration in the films. Both composition variation and ion migration under electric field are found to change the type of conductivity of the perovskite films, then modify their surface potentials and electron affinities. These are utilized to fabricate PVK‐based TENGs in pairs with poly‐tetrafluoroethylene (PTFE) or nylon films, respectively. Results show that PVK films are able to work as either a positive or a negative tribo‐material depending on the tribo‐material pair used; the optimal performances are obtained for PTFE/PVK TENGs using a PVK film with a MAI/PbI2 ratio of 2 and forward polarization, and for nylon/PVK TENGs using a PVK film with a MAI/PbI2 ratio of 0.4 and reverse polarization, respectively. The maximum output voltage and peak power density of PTFE/PVK TENGs are about 979 V and 24 W m−2, 2.5 and 6.5 times higher than those of TENGs with nonoptimal composition ratio or that are poorly polarized. This work provides a new material design method for high‐performance TENGs and a novel polarization strategy for TENG performance enhancement. [ABSTRACT FROM AUTHOR]

Rhombohedral NaZr2(PO4)3 is the prototype of all the NASICON‐type materials. The ionic diffusion in these rhombohedral NASICON materials is highly influenced by the ionic migration channels and the bottlenecks in the channels which have been extensively studied. However, no consensus is reached as to which one is the preferential ionic migration channel. Moreover, the relationships between the Na+ distribution over the multiple available sites, concerted migration, and diffusion properties remain elusive. Using ab initio molecular dynamics simulations, here it is shown that the Na+ ions tend to migrate through the Na1–Na3–Na2–Na3–Na1 channels rather than through the Na2–Na3–Na3–Na2 channels. There are two types of concerted migration mechanisms: two Na+ ions located at the adjacent Na1 and Na2 sites can migrate either in the same direction or at an angle. Both mechanisms exhibit relatively low migration barriers owing to the potential energy conversion during the Na+ ions migration process. Redistribution of Na+ ions from the most stable Na1 sites to Na2 on increasing Na+ total content further facilitates the concerted migration and promotes the Na+ ion mobility. The work establishes a connection between the Na+ concentration in rhombohedral NASICON materials and their diffusion properties. [ABSTRACT FROM AUTHOR]