[60]Fullerene assembly films consisting of C 60 and 1,2-diaminoethane (ethylenediamine) were easily fabricated on an amino-group-modified substrate by an alternate immersion process. The C 60 -assembly film was characterized after confirming the film formation using transmission absorption spectroscopy, transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. An inverted-type organic solar cell was fabricated by using the C 60 -assembly film as the acceptor layer in the photoactive layer of the solar cell. The resultant photoelectric conversion performances of the solar cells were evaluated using the photocurrent and photovoltage via the photoexcitation of polythiophene. The results suggested that the fabricated C 60 -assembly film works as an n-type semiconductor for polythiophene.Fullerenes are suitable as electron acceptor components in organic solar cells (OSCs), 1,2 artificial photosynthesis models, 35 and organic transistors; 68 they are highly attractive as organic n-type semiconductors. One of the reasons that fullerenes are efficient electron acceptors is their small reorganization energy in electron transfer.
911In OSCs, organic electronic material based photovoltaic devices such as dye-sensitized and organic thin-film solar cells have gained attention in novel renewable energy source applications because of their potential for low-cost, lightweight, and large-area processability.1214 Indeed, the carrier mobility of the organic films of the active layer is an important factor in the photoelectric conversion performance. 15,16 Controlling the orientation of fullerene assemblies is vital for fabricating useful fullerene-based n-type (acceptor) organic electronic materials. 1719 In particular, adjacent or aggregated fullerene structures seem to be suitable for fabricating n-type organic semiconductor materials or electron acceptor materials with high negative carrier mobilities. 2030 The number of fullerene derivatives exhibited as organic electronic materials is still limited compared with the number of donor material. 3133 Therefore, developing and improving a facile preparation method for fullerene derivatives is very important for the development of organic electronic materials.Additionally, the quality of the electric contact between the organic layer and the electrodes is one of the most important factors in determining device performance. 3439 One approach to improving the OSC performance is to modify C 60 -based selfassembled monolayers (C 60 -SAMs) at the interface between the inorganic and organic materials. 40,41 These C 60 -SAMs help suppress charge recombination between photoinduced holes and electrons at the inorganic/organic interface by preventing carrier trapping, as well as improving the photoinduced charge transfer properties.In relation to the above, one of the simplest chemical modification methods for the preparation of fullerene derivatives is an addition reaction between fullerenes and amines. 42,43 As the preparation method for C 60 -...