Study the effect of fullerene derivatives ratio on P3HT-based inverted organic solar cells

The inverted organic solar cell devices (iOSCs) were fabricated with different weight ratios 1:0.6, 1:0.8, and 1:1 of P3HT and PCBM, respectively. The photo-physical properties of these devices with varying weight ratios are investigated. We find that the absorption spectra revealed a decrease in the intensities with increasing the fullerene ratio and the peaks were blue shifted. Thin films morphology is evaluated by atomic force microscopy (AFM). The PL quenching suggests that the transfer of photo-induced electrons from P3HT to PCBM increases hugely with an increase in the amount of PCBM. Raman spectroscopy for devices shows a strong reduction in the crystallinity by increasing the ratio of fullerene within the blend. The J-V measurements for all devices were performed under the illumination of simulated AM 1.5 sunlight at 100 mW/cm2. External quantum efficiency (EQE) and Internal quantum efficiency (IQE) measurements are also performed for the best device. The best performance was recorded for the device with 1:1 weight ratio of P3HT and PCBM give Power Conversion Efficiency (PCE) of 3.67%, in contrast to 3.36% for (1:0.8) and 2.51% for 1:0.6 devices.