A study of the degradation process of quantum dots sensitized solar cells

Ha Thanh Tung, Bui Van Thang, Nguyen Thu Thao, Nguyen Tan Phat, Huynh Thanh Dat and Lam Quang Vinh

Abstract

In this work, quantum dots sensitized solar cells had been successfully prepared based on Cu₂S counter electrode and TiO₂/CdS/Cd_1-xMn_xSe/ZnS photoanode. The highest power conversion efficiency was 3.77%. Herein, we studied the degradation process of quantum dots sensitized solar cells by investigating the photocurrent-voltage (I-V) curves and electrochemical impedance spectroscopy. The results showed that there was a downward trend of the power conversion efficiency from 3.77% to 1.52%. This trend was proved by the increase of dynamic resistance, including: charge recombination resistance at counter electrode/electrolyte and FTO/TiO₂ interface (R_ct1 increased from 204.5 Ω to 780.1 Ω), charge transfer resistance within the TiO₂ film and at the TiO₂/QDs/electrolyte interface (R_ct2 increased from 24.65 Ω to 466.7 Ω). The decreased efficiency and increased dynamic resistance might cause the quantum dots sensitized solar cell degradation