Novel 9,9′-bifluorenylidene derivatives were designed to study the effect of alkyl chain length on selected physical properties. The structure of the synthesized compounds was confirmed by using NMR spectroscopy (¹H, ¹³C, H–H COSY, H–C HMQC, H–C HMBC) and elemental analysis. They showed high thermal stability and undergo decomposition in the range of 388–400 °C. As was revealed by DSC investigations, they can be converted from crystalline to amorphous materials with relatively high glass transition temperature. The replacement of the alkyl chains from ethyl to butyl resulted in a significant negative impact on melting and glass transition temperatures. The synthesized derivatives undergo reversible electrochemical oxidation and reduction and showed a very low energy band gap (1.47 and 1.79 eV). They intensively absorb the light up 550 nm and also exhibited a week absorption band in the range of 550–750 nm. Their hole transporting ability was tested in perovskite solar cells. Additionally, the effect of the doping concentration of Li⁺ on photovoltaic device performance for these compounds was investigated. It should be stressed found that 9,9′-bifluorenylidene derivative substituted with ethyl units applied as hole transporting materials in perovskite solar cells demonstrated the highest device efficiency of 7.33% higher than of the spiro-OMeTAD utilized for preparation of the reference cell (4.40%).

设计了新型9,9'-联芴基衍生物，以研究烷基链长对所选物理性质的影响。通过NMR光谱确认合成的化合物的结构（¹ H，¹³C，H–H COSY，H–C HMQC，H–C HMBC）和元素分析。它们表现出很高的热稳定性，并在388–400°C的温度范围内发生分解。DSC研究表明，它们可以在较高的玻璃化转变温度下从晶体材料转变为无定形材料。烷基链从乙基取代为丁基会对熔融和玻璃化转变温度产生重大负面影响。合成的衍生物经历可逆的电化学氧化和还原，并显示出非常低的能带隙（1.47和1.79 eV）。他们强烈吸收550 nm的光，并在550-750 nm的范围内表现出一周的吸收带。在钙钛矿太阳能电池中测试了它们的空穴传输能力。另外，Li ⁺的掺杂浓度的影响研究了这些化合物对光伏器件性能的影响。应当强调的是，在钙钛矿太阳能电池中用作乙基空穴传输材料的被乙基单元取代的9,9'-联芴基衍生物显示出最高的器件效率比用于制备参比电池的spiro-OMeTAD高7.33％（4.40 ％）。