Synthesis And Photovoltaic Properties Of New Fullerene Acceptor Molecules NAAFs Series

The rapid development of human society increase the requirement for energy, the solar cell has becoming one of the most popular research topics because it is one of the new friendly environmental energy. Polymer solar cells (PSCs) attracted the attention of many researchers because of its possessing several advantages such as light weight, mechanical flexibility, colourfulness, and compatibility for cheap and mass production compared with inorganic solar cells. Active layer in most polymer solar cells is composed of donor and acceptor materials, which fullerenes and their derivatives (eg. PC61BM and PC71BM) are frequently used as the acceptor materials. Fullerenes have been considered as ideal acceptor materials due to unique spherical molecular structures, which facilitate their interaction with donors in any directions; meanwhile, low LUMO levels and small reorganization energies render them high electron affinity and good electron mobility. However, complicated synthetic methods limited new and efficient fullerene materials. Till now only couple of fullerene mono-adducts, bis-adducts, and penta-adducts were used as acceptor materials in organic photovoltaic devices. To resolve such problem, a new and simple method is designed to synthesize a series of new and efficient fullerene materials. Specific content as follows:(1) A series of N-alkylaziridino[60]fullerenes (NAAFs) were successfully synthesized through the [2+1] reaction of C60and a series of primary alkylamines with the aid of di(acetoxyiodo)benzene (DIB) and I2under room temperature for30min in only one step, respectively. The synthesized compounds were characterized by’H-NMR,13C-NMR, FT-IR and MALDI-TOF-MS. Cyclic voltammetry was used to investigate the LUMO lever of the synthesized compounds. The thermal stability of synthesized compounds was measured by thermogravimetric analysis.(2) The photovoltaic performance of NAAFs in PSCs was carried out by fa brication of the BHJ devices with a typical structure ITO/PEDOT:PSS/fullerene: P3HT/Ca/Al. The results indicated that such series of N-alkylaziridino[60]fullerene s (NAAFs) showed good photovoltaic performance. Among all6NAAFs, the1-naphthalenemethyl and2-phenylethyl substituted aziridinofullerenes showed signifi cantly better performance than the others. The average PCEs for NNAF and NP EAF were2.39%and2.01%. When the molar ratio of fullerene and P3HT was0.5:1, the PCEs of all devices increased. The champion cell was based on NPE AF and P3HT blend (0.5:1,20mg mL-1) with a PCE of2.92%, a Voc of0.58V, a Jsc of7.5mA cm-2, and a fill factor of0.57. The effect of thermal anneal ing on the performance of the NPEAF devices was also investigated. Pre-anneali ng the active layer at150℃for10min significantly improved the Voc and FF of the devices. AFM images indicated that the film annealed at150℃has a b etter morphology with smaller domain size and ideal phase separation.