Degradation analysis of PCDTBT:PC71BM organic solar cells-an insight

Abstract

The current density-voltage (J-V) characteristics were measured for poly [N-9″-heptadeca-nyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzo-thiadiazole)]:[6,6]-phenyl-C71-butyric acid methyl ester (PCDTBT:PC71BM) solar cells and studied for degradation analysis up to 150 h of fabrication. It was observed that the dark J-V characteristics in the degraded cell could be explained using both drift-diffusion (D-D) model and space charge limited current (SCLC) model. The D-D model could explain the J-V characteristics at initial voltage region, while SCLC model fitted well in the later part. By comparing the experimental data with theoretical curves, it was found that the transition from D-D model to SCLC model depends on the span of degradation. The results indicated an increase of traps and decrease of charge carrier mobility which may lead to degradation of organic solar cells. This work gave an insight into the degradation mechanism influencing the performance of organic solar cells.