Preparation Of Perovskite Solar Cell By Two-step Solution Process And Research Of Its Photovoltaic Performance

Perovskite solar cells have drawn lots of attentions from the academic field in recent years. The perovskite absorption layer is one of the main components of the perovskite solar cell, which greatly affects its photovoltaic performance, In this thesis, the high-concentration of 1.9 M PbI2·NMP complex precursor solution in DMF was successfully prepared by batch-wise addition of PbI2 and NMP, repeated procedure of PbI2 dissolution and NMP addition, keep PbI2 excess to suppress PbI2·NMP2. The Br-doping CH3NH3PbI3-xBrx thin film with the feature of high-thickness, full-coverage and large-grain was obtained using two-step spin-coating solution method. The corresponding planar perovskite solar cell with the structure of FTO/c-TiO2/CH3NH3Pbl3-xBrx/spiro-OMeTAD/Au was assembled. The influence of PbI2·NMP complex precursor solution concentration, conversion temperature and conversion time, CH3NH3Br content of the methylammonium halide mixture solution in two-step spin-coating solution method on the chemical composition, optical absorption,crystal phase and microstructure of CH3NH3PbI3-xBrx thin films were systemically investigated and the photovoltaic performance of the corresponding planar perovskite solar cells was compared.The result revealed that the high-concentration PbI2·NMP complex precursor solution in DMF was successfully prepared by repeating the cycle of PbI2-dissolving and NMP-adding and when the PbI2·NMP complex precursor solution concentration increased from 1.5 M to 1.7 M, 1.9 M, the PbI2·NMP complex thin film thickness increased from 347 nm to 382 nm, 508 nm, the corresponding CH3NH3PbI3-xBrx thin film thickness increased from 444 nm to 538 nm, 596 nm. The planar perovskite solar cell based on the 1.9 M PbI2·NMP complex precursor solution obtained the best photoelectric conversion efficiency (PCE) of 12.13% and the average PCE of 11.90±0.49% in at the relative humidity of 50?54 %. When the conversion temperature raised from 100 ? to 120 ?, 140 ?, the conversion time decreased from 40 min to 20 min, 10 min,the grain sizes of the corresponding CH3NH3PbI3-xBrx thin films increased from ?250 nm to ?500 nm,?800 nm. The planar perovskite solar cell based on the conversion temperature and conversion time of 140 ? and 10 min achieved the best PCE of 13.56% and the average PCE of 12.46±1.10% at the relative humidity of 50?54 %. The Br contents in CH3NH3Pbl3-xBrx thin films linearly increased with the increase of Br contents in the methylammonium halide mixture solutions and the increase rate of Br contents in CH3NH3PbI3-xBrx thin films was lower than that in methylammonium halide mixture solutions. With the increased of the CH3NH3Br content in the methylammonium halide mixture solutions, the absorption onset of the resulting CH3NH3Pbl3-xBrx thin films gradually decreased and the 2? values of the (110)peaks slightly increased. The planar perovskite solar cell with the molar ratio of CH3NH3Br/CH3NH3I=10/90 achieved the best PCE of 14.88 % and the average PCE of 14.21 ±0.67%.