Polymeric hole-transporting material with a flexible backbone for constructing thermally stable inverted perovskite solar cells

Abstract

The explored p–i–n inverted architecture perovskite solar cells (i-PSCs) show promising application in flexible, large-scale and laminated photovoltaic technology. Polymeric HTMs for i-PSCs have been rarely reported. Thus far, only a commercial hole-transporting material, polytriarylamine (PTAA), has achieved a significant PCE of over 23% in i-PSCs. However, a perovskite precursor exhibits poor wettability on the PTAA films, thereby reducing their reproducibility and causing uncontrollable device instability. In this study, a type of binaphthyl-ether based polymer Z13 was developed through radical polymerization to replace the palladium catalyzed coupling reaction. A small molecule (Z5) and commercial PTAA were classified as the control. The comparatively flexible ether bond (–O–) of the backbone in Z13 improved the solubility and film forming properties of the material, thereby contributing to a superior morphology uniformity of the deposited perovskite. Consequently, promising device performance was achieved for i-PSCs endowed with Z13. The maximum power conversion efficiency of 18.80% obtained for Z13 was comparable with that of PTAA (19.02%), exceeding that with Z5 (18.48%). More importantly, Z13 films ensured a significantly optimized device thermal-durability as opposed to references PTAA and Z5. This study proposed a promising design for novel polymeric materials with low costs, high production reproducibility, favorable solubility and excellent optoelectronic properties.