The effect of annealing treatment on the performance of bulk heterojunction solar cells with donor and acceptor different weight ratios

Bulk heterojunction organic solar cells (OSCs) based on the blend of poly(2-methoxy-5(2′-ethyl-hexyloxy)-1,4-phenylenevinylene (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) with different weight ratios (from 1:3 to 1:5) have been fabricated and the effect of annealing treatment on the performance of OSCs has also been studied. Experimental results point to the best optimized doping concentration 1:4 for MEH-PPV:PCBM. Furthermore, it is found that the devices with annealing treatment at 150°C with 8 min show better performance compared with the devices without treatment. The series resistance (R s) is decreased, while the shunt resistance (R sh) increased by nearly 1.5 times. The short-circuit current density (J sc) and fill factor (FF) are improved by annealing treatment. As a result, the power conversion efficiency (PCE) of the devices increases from 0.49 % to 1.21 % with the ratio of 1:3 and from 1.09% to 1.42% with the ratio of 1:4.