Hole-Transporting Materials for Perovskite Solar Cells Employing an Anthradithiophene Core

A decade after the report of the first efficient perovskite-based solar cell, development of novel hole-transporting materials (HTMs) is still one of the main topics in this research field. Two of the main advance vectors of this topic lie in obtaining materials with enhanced hole-extracting capability and in easing their synthetic cost. The use of anthra[1,9-bc:5,10-b'c']dithiophene (ADT) as a flat pi-conjugated frame for bearing arylamine electroactive moieties allows obtaining two novel highly efficient HTMs from very cheap precursors. The solar cells fabricated making use of the mixed composition (FAPbI(3))(0.85)(MAPbBr(3))(0.15) perovskite and the novel ADT-based HTMs show power conversion efficiencies up to 17.6% under 1 sun illumination compared to the 18.1% observed when using the benchmark compound 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-OMeTAD). Detailed density functional theory calculations allow rationalization of the observed opto-electrochemical properties and predict a flat molecular structure with a low reorganization energy that supports the high conductivity measured for the best-performing HTM.