ACTIVE-LAYER THICKNESS DEPENDENCE OF THE DEVICE PERFORMANCE OF PCDTBT:PCBM POLYMER SOLAR CELLS AND THEIR STABILITY

摘要

The effect of active layer thickness on the performance of poly [N-9'-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) based solar cells was investigated. The active layer thickness of devices were varied following the approach of layer by layer growth. The cells were fabricated on an indium tin oxide (ITO)-coated glass substrate bearing the structure: ITO /poly(3,4- ethylene-dioxythiophene) (PEDOT:PSS)/PCDTBT:PC71BM/Al. It has been observed that the open circuit voltage (V_(oc)) gradually increases from 0.52 V for a single layer device to 0.80 V for a multilayer (5 layers) device. However, the short circuit current density (Jsc) is found to decrease from 17.33 mA/cm~2 to 7.51 mA/cm~2. Due to this reduction in current density the efficiency of multilayer devices is reduced down to 1.53% from 3.55% under 1 Sun illumination. The intensity variation experiments suggested that Jsc is monotonously increasing with the increase in input power and maintains a constant V_(oc) value. It has been inferred that that Jsc is not limited due to external fields but a pronounced recombination process is hindering a significant fraction of the separated charge to reach to respective electrodes. The device performance was significantly improved by thermal annealing of multilayered solar cells and an efficiency of 2.5 % was attained back.