A novel four-arm star-shaped (S) small molecule based on oligo(thienylfuran)s as conjugated arms and bithiophene (TT) as central core, was synthesized for solution-processable organic solar cells (OSC). To systematically investigate the characteristics of multi-dimensional conjugated systems, a two-arm linear-shaped (L) small molecule based on the same conjugated arms as that of S-TT was further synthesized. S-TT, as well as L-TT, both presented satisfactory solubility in common organic solvents. The nature of addition arms of S-(TT) exhibited better thermal stability than did L-(TT). According to the UV-vis measurements, the onset wavelengths of S-(TT) displayed a red-shift about 38 nm from solution state to film state, which is larger than that of L-(TT)(~7 nm). This implies that the addition conjugated arms of S-(TT) would incur a dense packing between molecules in film state. The tailoring of HOMO levels of L-TT and S-TT could be accomplished by utilizing the twisted central TT core. Computational analysis provided further evidences that the additional conjugated arms of multi-dimensional conjugated systems were capable of adjusting energy levels and electronic distribution. Inverted OSCs with ZnOx and MoO3 as an electron extraction layer and a hole extraction layer, respectively were fabricated by spin-coating the blend of L-TT or S-TT as donor and the fullerene derivative (PC61BM) as acceptor. The preliminary photovoltaic performances indicate that the photocurrent and power conversion efficiency were benefited greatly by inserting multi-dimensional conjugated arms in small molecule.