Abstract:
Developing air-stable high-performance small organic molecule based n-type and ambipolar organic field-effect transistors (OFETs) are very important and highly desirable. In this investigation, we designed and synthesized two naphthalenediimide (NDI) derivatives (NDI-BTH1 and NDI-BTH2), and found that introduction of 2-(benzo[d]thiazol-2-yl) acetonitrile groups at NDI core position gave lowest unoccupied molecular orbital (LUMO, -4.326 eV) and displayed strong electron affinities, suggesting that NDI-BTH1 might be a promising electron transporting material (i.e. n-type semiconductor). Whereas, NDI-BTH2 bearing bis(benzo[d]thiazol-2-yl)methane at NDI core with LUMO of -4.243 eV was demonstrated to be ambipolar material. OFET based on NDI-BTH1 and NDI-BTH2 have been fabricated and the charge carrier mobility of NDI-BTH1 and NDI-BTH2 are 14.00 x 10-5 cm2/Vs (mu e = electron mobility) and 8.64 x 10-4 cm2/Vs (mu e = electron mobility) and 1.68 x 10-4 cm2/Vs (mu h = hole mobility), respectively. Moreover, a difference in NDI-core substituent moieties significantly alters the UV-vis absorption and cyclic voltammeter properties. Thus, we further successfully employed NDI-BTH1 and NDI-BTH2 as an electron transport layer (ETL) materials in inverted perovskite solar cells (PSCs). The PSC performance exhibits that NDI-BTH2 as ETL material gave higher power conversion efficiency (PCE) as compared to NDI-BTH1 i.e. NDI-BTH2 produces 15.4 percent, while NDI-BTH1 gives 13.7 percent, respectively. The PSCs performance is comparable with the results obtained in OFET. We presume that improvement in solar cell efficiency of NDI-BTH2-based PSCs is due to the well-matched LUMO of NDI-BTH2 toward conduction band of perovskite layer, which in turn increase electron extraction and transportation.
