Formation of nanostructured fullerene interlayer through accelerated self-assembly and cross-linking of trichlorosilane moieties leading to enhanced efficiency of photovoltaic cells

A new cross-linkable fullerene material, bis(2-(trichlorosilyl)propyl)- malonate C₆₀ (TSMC), functionalized with two trichlorosilane groups, was easily synthesized by Pt-catalyzed olefin hydrosilylation. By making use of facile hydrolysis of the trichlorosilyl moieties, TSMC can be spontaneously self-assembled and cross-linked on the TiO_x surface by a simple spin-coating processing without the aid of photoirradiation or post-thermal treatments. The rapid formation of self-assembled and cross-linked TSMC (SA-C-TSMC) effectively passivates the residual hydroxyl groups on the TiO _x surface. More significantly, the solvent-resistant TSMC network features a nanostructured surface to provide extra charge-generating interfacial area and straight electron transport pathways. The device (ITO/TiO _x/SA-C-TSMC/P3HT:PC₆₁BM (1:1, w/w)/PEDOT:PSS/Ag) with this C₆₀ interlayer exhibited an efficiency of 3.9% which greatly outperformed the device without this layer. Furthermore, the strategy can also be effectively applied to the device (ITO/TiO_x/PDITTDTBT:PC ₇₁BM(1:4, w/w)/MoO_x/Ag) incorporating a conjugated polymer, poly(diindenothiophene-alt-dithienylbenzothiadizole) copolymer (PDITTDTBT). This device delivered a high efficiency of 5.8% which represents a 35% enhancement over the device without SA-C-TSMC. This new generation of trichlorosilane-based fullerene offers an easy and accelerated processing technique to produce efficient and cost-effective inverted solar cells.