Charge carrier transport properties in ternary Si-PCPDTBT:P3HT:PCBM solar cells

Abstract

In this work we investigate ternary blends of an active layer in bulk heterojunction solar cells and estimate the influence of their composition on solar cell parameters such as efficiency, mobility and recombination. The  studied ternary blends are composed of low bandgap polymer poly[2,6-(4,4-bis(2-ethylhexyl)dithieno[3,2-b:2,3-d]silole)-alt-4,7-(2,1,3 benzothiadiazole)] (Si-PCPDTBT), high bandgap polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) and fullerene derivative [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). The Langevin recombination reduction factor as well as charge carrier mobilities show an increasing trend with increasing Si-PCPDTBT content in the blends. The highest efficiencies have been achieved for the optimized blends of Si-PCPDTBT:P3HT:PCBM with ratios of 0.4:0.6:1, respectively.