Fullerene derivatives have been popularly applied as electron transport layers (ETLs) of inverted (p-i-n) planar heterojunction perovskite solar cells (iPSCs) due to their strong electron-accepting abilities, and so far, [6,6]-phenyl-C-butyric acid methyl ester (PCBM) has been the most commonly used ETL, which suffers, however, from high cost due to the complicated synthetic route. Herein, novel pyridine-functionalized fullerene derivatives (abbreviated as C-Py) were synthesized facilely via a one-step 1,3-dipolar cycloaddition reaction and applied as ETLs superior to PCBM in iPSC devices. Three pyridine-functionalized fullerene derivatives with different alkyl groups, including methyl, n-butyl, and n-hexyl, grafted onto the pyrrolidine moiety (abbreviated as C-MPy, C-BPy, and C-HPy, respectively) were synthesized. According to cyclic voltammogram study, the chain length of the N-alkyl group has negligible influence on the molecular energy level of C-Py. However, the ETL performance of C-Py is sensitively dependent on the chain length of the N-alkyl group, with C-BPy exhibiting the highest power conversion efficiency (PCE) of 16.83%, which surpasses that based on PCBM ETL (15.87%). The PCE enhancement of C-BPy device is attributed to the coordination interactions between the pyridine moiety with the Pb ion of CHNHPbI perovskite, which anchor C-BPy onto perovskite film and reinforce the passivation of the trap state within the CHNHPbI perovskite film and suppress the nonradiative electron-hole recombinations, leading to enhanced electron transport reflected by the increase of short-circuit current density ( J). The ambient stability of C-HPy-based device is much better than that based on PCBM ETL since its long N-alkyl group can function as a superior encapsulating layer protecting the CHNHPbI layer from contact with the ambient moisture.

A novel pyridine-functionalized fullerene derivative (C60-PyP) as an additive in regular bulk heterojunction perovskite (CH3NH3Pbl3) solar cells (PSCs) enables a power conversion efficiency of 19.82% with markedly suppressed hysteresis.

A new successive surface engineering method via a dual modification of TiO2 compact layer by PC61BM and C60-ETA was developed, affording dramatic efficiency enhancement with suppressed-hysteresis current–voltage response.

Graphitic carbon nitride (g-CN) as an emerging two-dimensional (2D) nanomaterial has been commonly used as a metal-free photocatalyst with potential applications in visible light photocatalytic water-splitting. However, the photocatalytic activity of g-CN is quite low due to its relatively large band gap and the existence of contact resistance between the nanosheets. Herein we report for the first time the facile synthesis of a covalently bonded g-CN/C hybrid via a solid-state mechanochemical route and its application in photocatalytic hydrogen production under visible light. The g-CN/C hybrid was synthesized by ball-milling g-CN and C in the presence of lithium hydroxide (LiOH) as a catalyst. The hybrid nature and conformation of the g-CN/C hybrid were confirmed by a series of spectroscopic and morphological studies, featuring the covalent bonding of C onto the edges of g-CN nanosheets via a four-membered ring of azetidine, which has never been reported in fullerene chemistry. The g-CN/C hybrid was further applied to metal-free visible light photocatalytic hydrogen production, affording a H production rate of 266 μmol h g without using any noble metal cocatalyst such as Pt, which is about 4.0 times higher than that obtained for the pristine g-CN photocatalyst.