Effect Of Interface Engineering For PEDOT:PSS Hole Transport Layer And Small Molecule Doped Active Layer On Organic Solar Cells Performance

Polymer solar cells have been attracted much attention because of its low cost,simple fabrication process,lightweight,large-area printing production,environmental friendliness in recent years.At present,the commercialization of polymer solar cell is limited due to its poor stability and low power conversion efficiency.The above-mentioned issues can be optimized by the development of new materials and device engineering method.In this paper,two kinds of device engineering were used to improve the performance of polymer solar cells.First,organic solvent post-treatment(Ethanol,dimethylformamide(DMF))method was used to improve the micro-morphology,carrier mobility,interface resistance of poly(3,4-ethylenedioxythio-phene):poly(styrene sulfonate)(PEDOT:PSS),and studied the influence on the performance of polymer solar cells.Second,the small molecule acceptor [(5Z,5’Z)-5,5’-(((4,4,9,9-tetraoctyl-4,9-dihydro-sindaceno[1,2-b:5,6-b’]dithiophene-2,7-diyl)bis(benzo[c][1,2,5]thiadiazole-7,4-diyl))bis(methanylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one)](O-IDTBR)is doped into poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b0]dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxy late](PTB7-Th):[6,6]-phenyl-C71-butyric acid methyl ester(PC71BM)binary blend system,and studied the effect on performance of the polymer solar cell.The purpose of this method is to enlarge the narrow light absorption range and reduce the charge recombination of polymer solar cells toward high efficiency devices.In order to improve the hole transport mobility,the ethanol dual optimization method was used to modify the PEDOT:PSS hole transport layer of poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)based polymer solar cells.The homogeneous PEDOT:PSS thin filmswere prepared on the surface of conductive glass ITO by solution-processed method using PEDOT:PSS aqueous solution mixed with 10 % vt ethanol.And then,the pure ethanol solution was dropped on the prepared PEDOT:PSS layer.It is found that the best performance of the devices is obtained by using ethanol dual optimization method,and the efficiency of the device is increased from 2.81 % to 3.29 % comparing with the control device.The results show that the dual optimization method can remove the PSS insulator on the PEDOT:PSS surface,but also improve the crystalline size of the PEDOT conductor,moreover,the aggregation of PSS was reduced.The results of PL and EIS showed that when ethanol dual optimizes the PEDOT:PSS transport layer,the charge recombination problem can be reduced and the carrier transport can be improved,and the space charge limited current(SCLC)results show that the ethanol dual optimization method can improve the hole transport mobility of PEDOT:PSS thin films.The PEDOT: PSS hole transport layer was prepared on the conductive ITO substrate glass by using the diluted PEDOT:PSS aqueous solution and studied the effect on the performance of polymer solar cells.It is found that the micro-morphology and optical properties of the film is improved and the FF of the device is increased from 52.41 % to 64 %.The SCLC results showed that the balance with the electron and hole transfer mobility were obtained.The AFM results showed that the aggregation size of the conductor PEDOT reduced to induce the reduction of hole transport mobility.The homogeneous post-treated PEDOT:PSS thin films were prepared through DMF dropping on the spin-coating PEDOT:PSS film prepared with the diluted PEDOT:PSS aqueous solution,and studied the influence on the performance of PTB7-Th:PCBM based polymer solar cells.It is found that the micro-morphology and optical properties of PEDOT:PSS film were modified.The device efficiency is increased from 6.34 % to 7.21 %.XPS and FTIR results showed that the DMF post-treatment washes out the insulator PSS on the surface of PEDOT:PSS film,which is beneficial to charge carrier mobility.The results of PL and EIS showed the suppression of charge carrierrecombination,which caused the improvement of the short-current density.In order to enhance the narrow light absorption range and low charge transfer mobility of binary blend polymer solar cells,the small molecular acceptor O-IDTBR doped into binary blend PTB7-Th:PC71BM system and studied the effect on the performance of PTB7-Th:PC71BM based polymer solar cells.The results showed that the ternary blended method is possible to reduce charge recombination,and improve short circuit current and open circuit voltage,thus enhance device efficiency.