Gold quantum dots (AuQDs) are employed as photosensitizers in organic thin-film solar cells (OSCs) to improve their photoelectric conversion properties. Three types of AuQDs with different fluorescence emission wavelengths are used: blue (B-AuQDs), green (G-AuQDs), and red (R-AuQDs). AuQDs are loaded into the poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) thin-film layer of OSCs. UV-vis spectra, atomic force microscope images, current density-voltage characteristics, and impedance spectra of the fabricated devices are measured for the three aforementioned types of AuQDs. All types of AuQDs improve the photoelectric conversion properties, and the G-AuQD-loaded OSCs exhibit the best improvement, exhibiting an efficiency increase of 10% compared with OSCs without the AuQDs. The fluorescence/photo-sensitization of the AuQDs plays an important role in the enhancement of the OSCs. Finite-difference time-domain simulations indicate increased electric field intensity due to a small degree of AuQDs aggregation.