The Study On Doping And Modification Of The Active Layer Of Perovskite Solar Cell

In recent years,the organic-inorganic hybrid perovskite solar cells（PSCs）have attracted extensive research due to its excellent photoelectric properties.Since 2009,power conversion efficiency（PCE）has grown rapidly from 3.8%to more than 25%.However,perovskite materials have poor environmental stability and are prone to degradation.In addition,expensive hole transfer materials（HTMs）and noble metal electrodes be used high usually in efficiency PSCs and the increase in cost hinders the commercial application seriously.Therefore,it is necessary to find a cheap electrode material to replace the use of noble metal electrode.In this paper,HTM-free PSCs were prepared by using carbon electrode instead of noble metal electrode in air environment.To improve its photoelectric performance and environmental stability of the device,PSCs were optimized from the aspects of modification of perovskite active layer and improvement of device structure.The main contents of this paper are as follows:（1）The influence of the change of micro Cs⁺ doping ratio on the performance of Cs_xMA_1-xPbI₃-based PSCs was studied with structure of FTO/Compact-TiO₂（C-TiO₂）layer/Mesoporous-TiO₂-ZrO₂（M-TiO₂）layer/perovskite layer/carbon counter electrode.It was found that when x was 0.05,the Csx MA1-x PbI₃ film was denser and the particle size of perovskite crystal was larger.Therefore,the perovskite film had better light absorption performance.High-quality perovskite film is the key to the improvement of photoelectric performance of devices.Finally,under the standard simulated solar illumination conditions,PSC based on Cs0.05MA0.95PbI₃ obtained up to 10.57%PCE,short circuit current density（Jsc）and open circuit optical voltage（Voc）were 21.73m A/cm² and 956 m V,respectively,and the filling factor（FF）was 0.509.In addition,the unencapsulated Cs0.05MA0.95PbI₃-based PSC demonstrated superior stability in the air environment.After 1000 hours,the Cs0.05MA0.95PbI₃ devices maintained more than90%of their initial PCE.The long-term stability can be attributed to the synergistic interaction of Cs⁺on the solid solution strengthening of MAPbI₃ and the protection of the hydrophobic carbon electrode on the Csx MA1-x PbI₃ layer.（2）Equal moles of PbI₂ and CH₃NH₃I（MAI）were dissolved in mixture solvent of DMSO and DMF with a volume ratio of 4:1.Then polyethylene glycol（PEG）additives of different weights were added to prepare perovskite precursors with concentrations of 0,5,10,15,20 and 25 mg/ml,respectively.The effects of PEG additives at different concentrations on the morphology and crystallinity of perovskite films were studied.The results showed that PEG-MAPbI₃ films with a concentration of 10 mg/ml exhibited high surface coverage and excellent crystallinity compared with other perovskite films,and obtained the strongest light absorption intensity.The structure of the assembled device was FTO/C-TiO₂ layer/M-TiO₂-ZrO₂layer/PEG-MAPbI₃/carbon counter electrode and the photoelectric performance was tested.The results showed that the PEG-MAPbI₃ based on concentration of 10 mg/ml exhibited the best photoelectric performance:Voc=982 m V,Jsc=21.68 m A/cm²,FF=0.546,PCE=11.62%。In addition,the strong moisture absorption of PEG long-chain molecules can absorb water molecules near perovskite crystal,which is conducive to avoiding perovskite destruction.Therefore,PSC shows super strong long-term stability based on the dual protection of carbon electrode and PEG.At the end of the 110-day aging test,the PCE of the PEG-MAPbI₃ device based on the concentration of 10 mg/ml did not decay.