Hole transporting materials based on benzodithiophene and dithienopyrrole cores for efficient perovskite solar cells

The development of highly efficient hole transporting materials (HTMs) for perovskite solar cells (PSCs) is still one of the most thrilling research subjects in the development of this emerging photovoltaic technology. Inner ring engineering of the aromatic core of new HTMs –consisting in three fused rings endowed with four triarylamine units– reveals major performance effects over the fabricated devices. In particular, substitution of the central pyrrole ring in dithienopyrrole (DTP) by a benzene ring –benzodithiophene (BDT)– allows enhancing the power conversion efficiency from 15.6% to 18.1%, in devices employing mixed-perovskite (FAPbI3)0.85(MAPbBr3)0.15 (MA: CH3NH3 +, FA: NH=CHNH3 +) under 1 sun illumination. In comparison, 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) yielded 17.7%. The novel HTM molecules show an efficient quenching of the perovskite photoluminescence, indicating an efficient charge transfer from the active layer to the HTM, along with a good conductivity (comparable to that of spiro-OMeTAD reference). Density functional theory (DFT) calculations allowed rationalizing the electrochemical and optical properties, and predict a reorganization energy (λ) for the best performing BDT-based HTM (0.101 eV) significantly lower than that computed for the benchmark spiro-OMeTAD (0.139 eV).European Research CouncilComunidad de MadridMINECOGeneralitat ValencianaEuropean Feder fundsMINECODepto. de Química OrgánicaFac. de Ciencias QuímicasTRUEpu

Hole-transporting materials for perovskite solar cells employing an anthradithiophene core

A decade after the report of the first efficient perovskitebased 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 π- 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 (FAPbI3)0.85(MAPbBr3)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-methoxyphenylamine)-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