A series of diketopyrrolopyrrole-based small molecules have been designed to explore their optical, electronic, and charge transport properties as organic solar cell (OSCs) materials. The calculation results showed that the designed molecules can lower the band gap and extend the absorption spectrum towards longer wavelengths. The designed molecules own the large longest wavelength of absorption spectra, the oscillator strength, and absorption region values. The optical, electronic, and charge transport properties of the designed molecules are affected by the introduction of different -bridges and end groups. We have also predicted the mobility of the designed molecule with the lowest total energies. Our results reveal that the designed molecules are expected to be promising candidates for OSC materials. Additionally, the designed molecules are expected to be promising candidates for electron and/or hole transport materials. On the basis of our results, we suggest that molecules under investigation are suitable donors for [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) and its derivatives as acceptors of OSCs.