Efficient Charge Transport in Ternary Organic Solar Cells by Two Donor Polymers with Identical Valence Bands
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초록
내용
Despite the potential of ternary organic solar cells (OSCs) to improve photocurrents, ternary architecture is not widely utilized for OSCs because its application has been shown to reduce fill factor (FF). In this paper, we report a novel technique for achieving highly efficient ternary OSCs without this characteristic sharp decrease in FF by matching the HOMO energy levels of two donor polymers. Our ternary device --- made from a blend of wide-bandgap PBDT-DPPD polymer, narrow-bandgap PTB7-Th polymer, and PC70BM--- exhibits a maximum power conversion efficiency of 10.42% with an open-circuit voltage of 0.80 V, a short-circuit current of 17.61 mA/cm2, and an FF of 0.74. In addition, we extend this concept to quaternary OSCs made by using three different donor polymers with similar HOMO levels. Interestingly, the quaternary OSCs also yield a good FF (~0.70) --- similar to those of corresponding binary OSCs.