p-n接合界面の色素修飾による高分子太陽電池の光捕集効率の向上

Abstract

p型半導体の共役高分子とn型半導体のフラーレン誘導体からなる高分子太陽電池に, 嵩高い軸配位子を有する近赤外色素を導入することで光捕集効率を効率よく向上できることを実証した. 色素の種類を増やすことで, 光電流をさらに増加させることも容易に実現できる. 過渡吸収分光法により光増感の素過程を観測したところ, 色素励起による電荷生成はほぼ100%の高効率過程であり, ほぼすべての色素がp-n接合界面に偏在していることが分かった. このような界面偏在は, 共役高分子の結晶化により色素が界面へ排斥される効果と, 色素の表面エネルギーが高分子とフラーレンの中間に位置するために界面活性剤的な性質を示す効果に起因していることを明らかにした.

The light-harvesting efficiency of polymer solar cells based on a conjugated polymer (p-type semiconductor) and a fullerene derivative (n-type semiconductor) can be effectively improved by incorporating near-IR dye molecules with bulky axial groups. Further improvement in the photocurrent can be easily obtained by incorporating different dye molecules that have complimentary absorption bands. Transient absorption studies have shown that all the primary processes in the dye sensitization proceed with almost 100% efficiency and that most of dye molecules are located at the p-n junction. Such interfacial segregation of dye molecules is partly due to crystallization of polymer matrix, which would expel dye molecules into the p-n junction, and partly due to intermediate surface energy of dye molecules between polymer and fullerene, by which dye molecules would serve as a surfactant in polymer/fullerene blends.