A new two-dimensional (2D) organic small molecule, DCA3T(T-BDT), was designed and synthesized for solution-processed organic solar cells (OSCs). DCA3T(T-BDT) exhibited a deep HOMO energy level (-5.37 eV) and good thermal stability. The morphologies of the DCA3T(T-BDT):[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) blends were investigated by atomic force microscopy and the crystallinity was explored by X-ray diffraction (XRD) and 2D grazing incidence wide-angle X-ray scattering (GIWAXS), respectively. The morphologies of the blends were strongly influenced by the blend ratio of DCA3T(T-BDT): PC61BM and annealing temperature. The effect of thermal annealing on the photovoltaic performance of DCA3T(T-BDT)-based small molecule organic solar cells (SMOSCs) was studied in detail. When DCA3T(T-BDT) was used as a donor with PC61BM as an acceptor, high efficiency SMOSCs with a power conversion efficiency of 7.93%, a high V-oc of 0.95 V, J(sc) of 11.86 mA cm(-2) and FF of 0.70 were obtained by a thermal annealing process at only 60 degrees C, which offers obvious advantages for large scale production compared with solvent additive or interfacial modification treatment.