Colloidal PbS quantum dots (QDs) with spectral tunability through quantum size effects were synthesized by chemical solution. By controlling the reaction temperature and preparing proper precursor, we obtained QDs with first absorption peak varied from 833 nm to 1706 nm. The structures, size distribution, and absorption properties of the QDs were measured by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and absorption spectra. Results showed that PbS quantum dots had narrow size distributions with diameters in the range of 2.6～7.0 nm. Based on the near infrared absorption properties of PbS QDs, we fabricated FTO/TiO2/PbS/Au solar cells by controlling the surface properties of PbS QDs on TiO2 film deposited with atomic layer deposition (ALD) and studied the relation between the photocurrent and the characteristic absorption peak of QDs.