To achieve light-harvesting efficiency more effectively, narrow-band-gap semiconductor quantum dots (QDs) have been the subject of considerable interest as a candidate for light harvesters alternative to organic dyes. The use of semiconductor QDs as photosensitizers has some advantages for sensitized solar cells. In this study, the optical absorption and ultrafasr carrier dynamics of nanostructured TiO₂ electrodes adsorbed with CdS QDs have been characterized by photoacoustic (PA) method and near-field heterodyne detection transient grating (NF-HD-TG) technique, respectively. PA method is effective for characterizing the optical absorption of opaque samples due to nonradiative processes. NF-HD-TG technique is a powerful time-resolved optical technique to characterize the photoexcited carrier dynamics including electron transfer from semiconductor QDs to TiO₂ electrodes for improving the photovoltaic conversion efficiency. Compared to conventional TG technique, NF-HD-TG technique is highly sensitive and is suitable for the measurements of rough solid samples. The shoulder part in PA spectrum, which is assumed to the first excitation energy of CdS QDs, are shifted to lower energy region with increasing numbers of the QD coatings, indicating the growth of CdS QDs. In the NF-HD-TG responses, two decay processes were observed. The fast decay one is the reflection of photoexcited hole relaxation, and the slow one corresponds to photoelectron relaxation processes, i.e., electron transfer and/or trapping. The decay time for fast decay process is almost constant for all the samples (3 ps). The decay time for slow decay process increases with the increase of growth for CdS QDs (40-80 ps).