The Study Of Crystalization Characteristics And Interface Modification Of Mixed Halide Perovskite Thin-films For High-efficiency Perovskite Solar Cells Devices

Because of the promising photoelectric-properties of metal halide perovskite solar cells(PVSCs),they have received widespread attention from academia and industry.With the tremenduous efforts dedicated by scientists to develop PVSCs,in just around 10 years,the power conversion efficiency(PCE)of PVSC has increased from 3.8%to 25.5%.However,there are still two major problems to be solved in the development of PVSC technology.One is the poor reproducibility of the photovoltaic performance of PVSC,and the other is the long term stability of the PVSCs that requirse to meet commercial standards.This thesis focuses on using composition and interface engineering to tackle the stability of PVSCs and the results will be discussed in the following two chapters:In the second chapter,by studying the concentration of the perovskite precursor solution,the annealing temperature of the perovskite,the solvent composition of the perovskite precursor solution,the type of antisolvent,and the ratio of Br and I in the perovskite precursor solution,this thesis sumarizes the influenue of these five factors on the morphology,surface roughness and crystallization characteristics of perovskite thin-films,the photovoltaic parameters(PCE,FF,J_sc,V_oc)of the perovskite solar cells,and the carrier recombination of the devices,etc.My results suggest best PVSCs can be obtained with optimal preparation and processing conditions,such as 1)an optimal range of concentration between 1.2-1.4 mmol/ml for the perovskite precursor solution;2)an optimal annealing temperature between 90-120?for the perovskite films,either too low or too high the temperature will cause internal defects of the perovskite crystal and reduce the performance of the devices;3)the presence of DMSO in the perovskite precursor solution plays an important role in perovskite crystallization and improves device performance,however,the proportion of DMSO only affects the processing conditions,but causes little effect on the PSVCs performance;4)the ratio of Br to I in the perovskite precursor solution also has a great influence on the crystallization characteristics of the perovskite thin-films and the performance of the devices.In the third chapter,a series of newly designed polymer materials composed of derivatives of triphenylamine and IDTT were introduced as hole transport materials for PVSCs.By careful evaluation of the electrical and electronic properties of the polymers,the polymer,P6,which has mobility and energy level matching better than that the most commonly used hole transporting material Spiro-OMeTAD,was chosen to be the hole transport layer for the PVSCs.We systematically optimized the solution concentration,annealing temperature and doping of P6,as a result,the PCE of P6-based PVSCs increased from 8%to 19%.In the doping research of P6,we found that the F4-TCNQ dopant is not efficent for doping of P6,while other dopants including Li TFSI and Tbp were found to be more suitable for improving the P6-based PVSCs.Finally,we performed stability tests for the PVSCs under different condictions including light soaking,nitrogen atmosphere storage and exposure to humidity.By tracking their performance under maximum powerpoint(MMP)condition,we conclude that the P6-based PVSCs show much better stability than the one based on Spiro-OMeTAD for all the three testing conditions.In summary,P6 is a better hole transporting material than Spiro-OMeTAD for PVSCs,showing higher device performance and stability.