Research On Low-temperature Preparation Technology Of Flexible And High-efficiency Perovskite Solar Cells

The low-temperature optimizing process for perovskite solar cells has been investigated and the optimal process has been employed to fabricate flexible perovskite solar cells in this paper.The volume ratio of SnO₂ and deionized water in precursor solution for electron transport layer,the annealing temperature for perovskite absorption layer and the concentration of potassium ion doped in precursor solution for perovskite absorption layer have been optimized.Finally,the optimal low-temperature process has been employed to fabricate flexible perovskite solar cells.The details are discussed as follows:First,the effect of low-temperature process for electron transport layer on the quality of perovskite film and the performance of perovskite solar cells has been investigated in Chapter 3.The volume ratio of SnO₂ and deionized water in precursor solution for electron transport layer has been changed to study the perovskite film quality and device power conversion efficiency.It is observed that the optimal perovskite film quality and device performance have been achieved when the ratio is set at 1:3,which gives a power conversion efficiency of 16.43%,a open circuit voltage（VOC）of 0.97 V,a short circuit current density（JSC）of 25.89 m A/cm² and a filling factor（FF）of 65.57 %.In addition,the extent of hysteresis for perovskite solar cells is fairly low.Secondly,the effect of preparing process for PbI₂ layer and annealing temperature for two-step solution-processed perovskite absorption layer on the performance of perovskite solar cells has been investigated in Chapter 4.In the first part,the device based on annealed PbI₂ layer is compared with that based on PbI₂ layer without annealing process.In the second part,the annealing temperature for as-grown perovskite layer（formed when MAI precursor solution is spin-coating on PbI₂ substrate）has been changed to monitor the device power conversion efficiency.It is observed that the optimal performance of perovskite solar cells is achieved when the as-grown PbI₂ film is annealed on the hot-plate at 70 ℃ for 20 min and the as-grown perovskite layer is annealed on the hot-plate at 150 ℃ for 20 min,which gives a power conversion efficiency of 16.43 %.Thirdly,the effect of concentration of potassium ion in precursor solution for perovskite concentration on the performance of perovskite solar cells has been investigated in Chapter 5.It is observed from Hall effect test that the majority of carriers in perovskite layer have changed from n-type to p-type after potassium ion doping.In addition,the Hysteresis Index for perovskite solar cells has been significantly reduced in the presence of potassium ion.This study shows that potassium ion doping could reduce the hysteresis of the device as well as change the majority types of carriers in perovskite layer.Finally,the optimal low-temperature process in this work has been employed to fabricate flexible golden-electrode perovskite solar cells,which gives a power conversion efficiency of 7 %.Furthermore,the mechanical bending measurement（by fingers with a bending radius of 5 mm）is performed for flexible perovskite solar cell,demonstrating that the device power conversion efficiency decreased to 46 % of the original value under bending conditions.