Organic bulk-heterojunction injected perovskite films for highly efficient solar cells

Abstract

Unsatisfactory light-harvesting over the wavelength of 500 nm is a critical factor limiting the further improvement in efficiency of halide lead based perovskite solar cells (PSCs). Past studies on a tandem strategy of integrating perovskite and bulk-heterojunction (BHJ) increased the fabrication complexity. Here, we developed a convenient strategy, injecting the organic BHJ of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]-thieno-[3,4-b]thiophenediyl]] (PTB7) and 3,9-bis[2-(3-oxo-2-vinyl-2,3-dihydroinden-1-ylidene)-malononitrile]-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC) via anti-solvent engineering. Besides the function of enhanced light-harvesting in the range of 500–700 nm for the perovskite layer, the BHJ-treated CH₃NH₃PbI₃ films exhibit superior crystalline quality with reduced defect and trap states. As a result, the resulting PSCs deliver a champion power conversion efficiency as high as 20%. The proposed method provides a facile route to integrate perovskite and organic BHJ conveniently by avoiding additional fabrication steps. And this method is suitable for large-scale and industrial production of high-performance PSCs.