A thieno[3,2-b]thiophene-functionalized porphyrin molecule (DEP-TT) with the ethynylene bridges between the diketopyrrolopyrrole and porphyrin units has been designed and synthesized as the donor material. DEP-TT exhibits a broad absorption wavelength in the visible region with the onset absorption to 898 nm of the film and a low optical band gap of 1.38 eV. IDT-C8, as the acceptor material has a relatively strong absorption spectrum ranging from 500 to 750 nm in the solid film, which exactly fills the absorption trough of DEP-TT. The power conversion efficiency (PCE) of all small molecule increased from 0.64% (J_sc = 2.61 mA cm⁻², V_oc = 0.82 V, and FF = 0.30) to 5.14% (J_sc = 11.15 mA cm⁻², V_oc = 0.71 V, and FF = 0.65) after solvent vapor annealing. The PCE of 5.14% provided valuable recommendation based on porphyrin all small molecule system, since few work has involved in this field.