The Study On The Efficiency And Stability Of The Inverted Planar Perovskite Solar Cells

In recent years,perovskite solar cells have stood out and set off a widespread research upsurge owning to many advantages,such as good light harvesting,long charge carrier diffusion,solution processability,low cost and so on.The research on perovskite solar cells is in full swing,achieving tremendous progresses.The power conversion efficiency?PCE?of perovskite solar cells has exceeded 22%within the last few years.The current PCE of perovskite solar cells is comparable to that of commercial silicon-based solar cells.However,there is still a big gap in the device lifetime and long-term stability.Stability is the bottleneck restricting the continuous development of perovskite solar cells.Synchronously improving the PCE and stability is the precondition of commercialization for perovskite solar cells,which is of great application value and practical significance.With the purpose of fabricating efficient and stable perovskite solar cells,we focus on realizing the controllable crystallization and reproducible preparation of high-quality perovskite films,fixing the microstructure of perovskite to make perovskite material and device more stable,as well as modifying the interface between the perovskite active layer and the charge transport layer through passivating defects and improving interfacial contact.The main contents are as follows:1.We employ a mixture of PbCl₂:PbAc₂ as lead sources and prepare the perovskite films via the two-step sequential deposition method.The two anions of Cl^-and Ac^-are introduced into the X site of ABX₃ perovskite,which combines the advantages of Cl^-and Ac^-anions to regulate the crystallization kinetics of perovskite.Based on the optimized PbCl₂:PbAc₂ ratio in the first-step precursor solution,we focus on the influence of substrate-preheating treatment on perovskite crystal film growth.It is demonstrated that the substrate-preheating treatment affects the crystal growth by influencing the intermediate phase composition and morphology.The controllable crystallization and the reproducible preparation of the high-quality perovskite films are realized through appropriate substrate-preheating treatment.The champion device exhibits high PCE of 12.48%,decent fill factor?FF?of 71.39%,short-circuit current density?Jsc?of 18.36 mA/cm² and open-circuit voltage?Voc?of 0.95 V.After a storage in glove-box for 20 days,the PCE of the device is 10.63%,only losing 15%of the initial value.2.1,6-Diaminohexane Dihydrochloride?1,6-DD?is added into perovskite precursors.The two terminal-NH₃⁺groups of 1,6-DD can dominate an A vacancy?empty A site?at the perovskite crystal surface,through forming the N-H…I^-hydrogen bond between the terminal-NH₃⁺and the I^-of the[PbI₆]^4-framework.Therefore,the 1,6-DD molecule passivates the defects on the perovskite crystal surfaces,and at the same time links the adjacent crystal surfaces through the hexane alkyl chain.The connection between adjacent crystal surfaces enhances the interaction between perovskite grains,responsible for fixing the microstructure of perovskite,which improves the stability of perovskite material and device.Compared to the control devices based on pristine perovskite,the average PCE of the 1,6-DD based devices is increased by 20%.The champion device achieves a relatively high PCE of 16.04%,a Voc of 0.99 V,a Jsc of 21.25 mA/cm² and an excellent FF of 76.24%.After exposure to the air for16 days,the device with 1,6-DD additive still retains above 90%of the initial value,exhibiting good stability.3.PCBM doped with BCP is employed as a novel electron transport layer?ETL?for the first time.The introduction of an appropriate amount of BCP ameliorates the film formation property of PCBM and improves the interfacial contact.The BCP molecule contains nitrogen atoms with lone pair which can effectively passivate the halide vacancy defects of perovskite thin film,suppressing the charge recombination and facilitating the charge transport and separation at the interface.Compared to the control device based on pure PCBM ETL,the PCE of the champion device based on PCBM:BCP blend ETL is up to13.11%,which is nearly doubled.BCP doping also significantly increases the hydrophobicity of the perovskite/PCBM surface,promoting the device stability.In addition,the PCBM:BCP blend ETL realizes the synchronized preparation of electron transport layer and hole blocking layer.It simplifies the device fabrication procedure,with promising application in large-scale production.4.DMSO and ionic iridium complex are introduced into PEDOT:PSS to modify the hole transport layer?HTL?.The introduction of DMSO improves the phase separation of PEDOT:PSS and is beneficial to the formation of better PEDOT conductive channels.The ionic iridium complex has a highly conjugated structure which is helpful for hole transport.And its introduction enhances the hole transmission capacity of PEDOT:PSS,further improving the conductivity of PEDOT:PSS HTL.Thus,more effective hole transport between the perovskite and the anode is realized.The modified PEDOT:PSS increases the PCE of perovskite solar cells from 16.04%to 17.08%,and has no negative influence on the stability of device.