A thin-film memory device is proposed herein, based on quantum dots (QDs) with bi-stable characteristics under a positive voltage bias. The synthesized QDs had a CdSe/ZnS core/shell structure. The charge confinement effect within the QDs in the charge-storage layer was enhanced by adding (poly(9-vinylcarbazole)) (PVK). As the PVK concentration increases, the on/off ratio of the device increases. Noise was also reduced and stable I-V characteristics were demonstrated. Each thin film was fabricated by a spin-coating method, among solution process methods. The on/off ratio of the fabricated device was found to be maximum 378 x 10(3) at 1.5 wt% PVK concentration. The initial on/off state was maintained even when a negative voltage (commonly used for the "erase" function) was applied. In addition, the write voltage of the fabricated device using the conductive polymer polyTPD was reduced from 2.8 to 1.7 V. By optimizing PVK concentration and forming the poly-TPD thin film, the fabricated memory device had an on/off ratio of about 4 x 10(3) at 0.5 V and the stored current maintained the initial value even after 200 h. Even with a single write process, the initially formed high state is maintained for more than 200 h, and it is possible to read repeatedly.