This study reports a new nonfullerene electron transporting material (ETM) based on naphthalene diimide (NDI) small molecules for use in high-performance perovskite solar cells (PSCs). These solar cells simultaneously achieve high power conversion efficiency (PCE) of over 20% and long-term stability. New NDI-ID (N,N′-Bis(1-indanyl)naphthalene-1,4,5,8-tetracarboxylic diimide) consisting of an N-substituted indane group having simultaneous alicyclic and aromatic characteristics is synthesized by a low-cost, one-step reaction, and facile purification method. The partially flexible characteristics of an alicyclic cyclopentene group on indane groups open the possibility of lowtemperature solution processing. The conformational rigidity and aromaticity of phenyl and alicyclic groups contribute to high temporal stability by strong secondary bonds. NDI-ID has herringbone packed semiconducting NDI cores that exhibit up to 0.2 cm 2 V −1 s −1 electron mobility in field effect transistors. The inverted PSCs based on CH(NH 2 ) 2 PbI 3-x Br x with NDI-ID ETM exhibit very high PCEs of up to 20.2%, which is better than that of widely used PCBM (phenyl-C61-butyric acid methyl ester) ETM-based PSCs. Moreover, NDI-IDbased PSCs exhibit very high long-term temporal stability, retaining 90% of the initial PCE after 500 h at 100 °C with 1 sun illumination without encapsulation. Therefore, NDI-ID is a promising ETM for highly efficient, stable PSCs.

Highly efficient and thermally stable inverted MAPbI3 and FAPbI3−xBrx perovskite planar solar cells are demonstrated by using a N,N′-bis(phenylmethyl)naphthalene-1,4,5,8-tetracarboxylicdiimide (NDI-PM)-based electron transporting material (ETM) instead of a conventional PCBM-based ETM.

A design strategy is proposed for electron‐transporting materials (ETMs) with homochiral asymmetric‐shaped groups for highly efficient non‐fullerene perovskite solar cells (PSCs). The electron transporting N,N′‐bis[(R)‐1‐phenylethyl]naphthalene‐1,4,5,8‐tetracarboxylic diimide (NDI‐PhE) consists of two asymmetric‐shaped chiral (R)‐1‐phenylethyl (PhE) groups that act as solubilizing groups by reducing molecular symmetry and increasing the free volume. NDI‐PhE exhibits excellent film‐forming ability with high solubility in various organic solvents [about two times higher solubility than the widely used fullerene‐based phenyl‐C61‐butyric acid methyl ester (PCBM) in o‐dichlorobenzene]. NDI‐PhE ETM‐based inverted PSCs exhibit very high power conversion efficiencies (PCE) of up to 20.5 % with an average PCE of 18.74±0.95 %, which are higher than those of PCBM ETM‐based PSCs. The high PCE of NDI‐PhE ETM‐based PSCs may be attributed to good film‐forming abilities and to three‐dimensional isotropic electron transporting capabilities. Therefore, introducing homochiral asymmetric‐shaped groups onto charge‐transporting materials is a good strategy for achieving high device performance.