Influences of structural modification of naphthalenediimides with benzothiazole on organic field-effect transistor and non-fullerene perovskite solar cell characteristics Shaikh

One of key factorst od esign applicable electron transport layers (ETLs) for perovskite solar cells is the morphology of ETLs since ag ood morphology would help to facilitate the carrier transport at two interfaces (perovskite\ETL and ETL\cathode). However,o ne drawback of most organic ETL smallm olecules is the internal undesired accumulation, which would cause the formation of inappropriate morphology and rough ETL surface. Here, by elaborately designing the side chains of NDI derivatives, the molecular interaction could be modified to achievet he aggregation in different degrees, whichw ould eventually affect the accumulation of molecules and surfaceq ualities of ETLs. By speculating from the comparison between the absorption spectra of solutions and films, the sequence of extent of molecule interaction and aggregation was built among three NDI derivatives, which is furtherc onfirmed by direct evidence of atomic force microscopy (AFM)i mages. Then, carrier exaction abilities are simply studied by steady-state photoluminescence spectroscopy.T he carrier transport process is also discussed based on cyclic voltammetry,t ime-resolved photoluminescence spectroscopy and mobility.N DIF1 are proven to have the appropriate internal aggregation to smooth the contact with cathodea nd low series resistance, and ad evice performance of 15.6 %i sa chieved. With the ability of preventing the thermal diffusion of Ag towards the perovskite surface due to the strongi nteraction between molecules, NDIF2 at high concentration shows the highest fill factor (80 %).

Novel dithiafulvenyl (DTF)‐naphthalenediimide (NDI) derivatives DS1 and DS2 has been designed, synthesized and characterized. To replace the costly PCBM in inverted perovskite solar cells (PSCs), we here propose these materials. DS1 and DS2 were employed as electron transport layers (ETL) to fabricate inverted PSCs based on CH3NH3PbI3‐xClx. The best power conversion efficiencies (PCEs) of inverted PSCs based on DS1 and DS2 exhibit 9.6% and 11.4%, respectively. The difference in PCE values revealed that DS2 bearing two DTF moieties on NDI core could enhance the PCE compared to DS1 containing one DTF moiety. Our results suggest that NDI‐based small molecules could be employed as a promising ETL in inverted PSCs to achieve high efficiency.