KCS

ye-sensitized solar cells (DSSCs) have been considered a promising alternative to the silicon-based solar cells due to their low-cost production and simple device fabrication. DSSCs using liquid electrolytes of Co^II/Co^III redox couples have shown efficiencies surpassing 12%. However, the stability issues of the DSSCs devices arise from leakage and evaporation of liquid electrolyte. Many efforts have been made to replace liquid electrolytes with quasi-solid-stateelectrolytes or solid-state hole conductors to alleviate the stability issues. However, the photovoltaic power conversion efficiency of solid-state DSSCs (ssDSSCs) remains significantly below that of liquid electrolyte-based devices. Recently, the organometal halide perovskites (CH₃NH₃PbX₃, X = Cl, Br, I) have attracted great attention due to their direct band gap, large optical absorption and high mobility. An impressive photovoltaic performance was achieved over 15% power conversion efficiency using 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) as a hole transporting material (HTM). The most effective HTM for the hybrid solar cells is spiro-OMeTAD, even though another small molecule HTMs such as 3,4-ethylenedioxythiophene-, pyrene-, linear π-conjugated structure, butadiene-, and swivel-cruciform thiophene- based HTMs gave high conversion efficiencies of 10~13%. However, the high synthetic cost of spiro-OMeTAD gives another problem for the commercialization. Therefore, the development of cost-effective HTMs with high efficiency and long stability is very important. We report new types of hole transporting materials with donor-π-acceptor (D-A) systems by incorporating an electron-deficient 1,3,5-triazine core and an electron-rich diphenylamino unit.