Synthesis Of Indolo[2,3-b] Carbazole-based Photosensitizers And Their Application In Dye-sensitized Solarcell And Perovskite Solarcell

Organic photosensitizers can excited by photon and result in injection of electrons into the conduction band of the oxide.Therefore,photosensitizers play an important role in the photogenerated electron process in dye-sensitized solar cells.In recent years,research on organic photosensitizers has become more and more intensive.Researchers have made many efforts in the spectral response capability,energy level matching,and electronic push-pull structure of photosensitizers.By adjusting the molecular structure,designing and synthesizing organic photosensitizers with high molar extinction coefficient,excellent spectral response and suitable energy level is of great significance for the application of dye-sensitized solar cells.In this work,a new type organic photosensitizer based on Indolo[2,3-b]carbazole was designed and synthesized.Indolo[2,3-b]carbazole is an ideal electron-donating moiety and has been used in DSSCs.However,the low redox potential of I^-/I₃^-and transitions from I^-/I₂^-to I^-/I₃^-lead to significant energy loss,and this limits the photovoltage.The sensitizer SK201and SK202 have suitable energy levels that can be used in conjunction with cobalt electrolytes.Moreover various alkoxy and alkyl chains which may inflict intramolecular charge separation were introduced onto donor segment to enhance solubility of dyes and alleviate the unfavorable intermolecular aggregation and charge quenching between excited molecular.SK202 contains a thienyl group between the donor and acceptor,whereas in SK201 the donor and acceptor are connected directly by a single bond.Introduction of a thienyl group improved the planarity of the dye molecule,broadened the absorption spectrum,reduce the energy loss of the injection driving force.DSSCs based on SK202 gave a power conversion efficiency?PCE?of 11.0%(J_sc 16.5 mA cm^-2,V_oc 932 mV,and fill factor 71.7%)with Co?II/III?complex based redox couple and the PCE maintain 95%of the initial level after 1000 hours in dark condition.In addition,I^-/I₃^-based devices also give an excellent PCE of 10.5%(J_sc 17.5 mA cm^-2,V_oc 844 mV,and fill factor 71.1%).This result means than SK type sensitizers were not sensitive to different redox couple and provide an effective strategy for designing new efficient organic dyes for DSSCs.In recent years,organic-inorganic hybrid perovskite based solar cells are one of the most fast-growing research fields in the photovoltaic.Halide perovskite materials have strong spectral response in the visible region,high extinction coefficient,long carrier lifetime and diffusion length?100nm-1?m?,and have p-n junction characteristics and the solid state photovoltaic device can be conveniently prepared by a simple solution processing method.However,the perovskite materials are made of polycrystalline morphology,which can easily beget all kinds of trap states at the surface and grain boundaries?include under-coordinated metal cations or halide anions?,acting as carrier recombination centers and causing the decomposition of perovskite.Herein,we employed a large molecular organic dye SK202 with–COOH functional group as passivator in the one-step antisolvent solution processing method.The passivated device effectively reduces carrier recombination and significantly increases the open circuit voltage.Moreover,due to the hydrophobic structure of SK202,the passivated perovskite film shows good hydrophobicity,and can maintain the initial efficiency of more than 80%after being placed in the air for 20 days.