Fine-tuning Side Chain Engineering Of Wide Band-gap Donors To Optimizie The Properties Of Organic Solar Cells

Organic solar cells(OSCs)have attracted great attention in recent years.Similar to the inorganic silicon solar cells which have realized industrialization,OSCs also is a high efficient and environmental protection photovoltaic device.Something different,the application prospect of OSCs is more widespread for their advantages such as flexibility,light weight,and low-cost production.Those advantages will be in favour of processing the flexible device,means that OSCs photovoltaic device are easier applied in our daily life than inorganic silicon solar cells.In the past decades,the core of device parameter power conversion efficiencies(PCEs)of the single-junction OSCs recently up to 16%.The one of effective core way to improve PCEs is designed and synthesized new donors/acceptors materials.At present,the most polymer main chain of high-performance donor materials was composed by electron-rich alternates with electron-deficient unit.These polymers which possessed high absorption coefficient,favourable phase separation size,and regulable energy levels,have been extensively studied in recent year.However,these polymer donors still face great challenge inculding the poor solubility,low polymerization activity and high processing requirements.Fine-tuning side chain engineering,which is benefited for solubility improvement and optimized the molecular morphology,becomes the one of important molecular design strategy to optimize donor materials.The result show that subtle regulation of side chain length of FTAZ unit exerted a significantly influence on absorption coefficient,molecular face-on orientation,phase separation size and active layer morphology.At last,L810 exhibited high PCE up to 12.1% with the all improved device parameters,including open-circuit voltage(Voc),short-current density(Jsc)and fill factor(FF)were all-round improvement.Intriguingly,the external quantum efficiency(EQE)values of L810:IT-4F-based device kept constantly up to 80% from 500 to 800 nm,which is one of the highest values reported for FTAZ-based PSCs so far.