Study On The Performance Of Super-flexible All-polymer Organic Solar Cells

Energy is a necessity to maintain people’s daily life,and it is also vital to national economic development.As a clean,abundant and popular renewable energy,solar energy can alleviate the pressure of energy shortage faced by people.Although solar cells had been widely used in energy saving and environmental protection,many new applications require them to have good flexibility with light weight and high temperature resistance.Therefore,it is particularly important to fabricate highly flexible transparent conductive electrodes(TCEs)and flexible organic solar cells(OSCs).In this paper,the mechanical flexibility and high temperature resistance characteristics of polyimide(PI)are systematically described first,including the research background of polyimide/conductive electrode,mechanical simulation,bending measurement.The flexibility of the TCEs and OSCs is described by introducing mechanical parameters such as Young’s modulus.Secondly,PI/Ag NW TCE was studied in comparison with the PI/ultrathin Ag and the commerical PET/ITO electrodes after 30,000 cycles of bending with a bending radius of 3 cm,in which the PI/Ag NW showed the best flexibility due to the stable morphology.Considering Young’s modulus and breaking elongation ratio of the three substrates,it is concluded that the flexibility of PI/Ag NW electrode is better than that of PET/ITO and PI/Ag TCEs.Flexible nonfullerene small molecular OSCs were fabricated using PM6:Y6 as the active layer and PI/Ag NW and PET/ITO as the TCEs,respectively.A high power conversion efficiency(PCE)of 13.40% was achieved for the PI/Ag NW based device,while only 5.78% for the PET/ITO based device due to the lower annealing treatment temperature about 100 ℃ for the PET/ITO/Zn O substrate.In order to explore the flexibility of the device,the relative changes of PCE,Voc,Jsc and FF were measured under different bending cycles with a radius of 3 mm.The results showed that the PI/Ag NW based OSC retained 93.6% of the initial PCE after bending 800 times at a radius of 3 mm,which is related to the stable film morphology and electrical parameters under bending.Compared to the small molecular nonfullerene acceptors,nonfullerene polymer acceptors have better flexibility and thermal stability.In the part,a polymer acceptor of PYF-T-o was used,which showed a high PCE of 12.42% for the PI/Ag NW based flexible all-polymer solar cell.Compared with the small molecular nonfullerene system of PM6:Y6,the PM6:PYF-T-o allpolymer system showed better flexibility.The device can retain 99.3% of the initial PCE after bending 800 times at a radius of 3 mm.Based on the morphology and electrical analysis,it is concluded that PI/Ag NW based all-polymer OSCs have the best flexible characteristics,indicating that they have broad application prospects in the flexible solar field.