Study On Preparation Technology Of CsPbI₂Br Perovskite Solar Cell And Tandem Device

In recent years,the efficiency of perovskite solar cells(PSCs)has rapidly increased from 3.8%to 24.2%in only 10 years,which can be considered to be the competitive for the next generation of photovoltaic technology.Although the rapid development of efficiency,the improvement in stability and economic processing have been concentrated on for commercialization of PSCs.In this work,aming at dreasing manufacturing cost and improving stability of the PSCs,we focus on the study of all-inorganic CsPbI2Br perovskite due to its phase and thermal stability.The effect of Pb(SCN)2 additive on the film quality of CsPbI2Br perovskite film was explored.The optimized CsPbI2Br PSC was used as the bottom sub-cell,and MAPbI3 PSC was prepared as the top sub-cell by vacuum evaporation and solution method,and finally 2T all-perovskite tandem cell was integrated.We have found that this vacuum-deposition protocol method can effectively solve solvent penetration problem during the fabrication progress of the sub-top cell for tandem devices.The specific details are as follows:(1)When the amount of Pb(SCN)2 is 1.0%(molar ratio),a 425 nm-thick CsPbI2Br film characteristics of high crystalline and smooth and even surface is obtained by passivating the grain boundaries with Pb(SCN)2 under low temperature(150?).A series of opto/electrochemical technology results demonstrate that the trap density of the CsPbI2Br film is greatly reduced with Pb(SCN)2,which effectively inhibits the interface recombination and promotes charge transport in CsPbI2Br PSC.The optimal CsPbI2Br films are assembled into PSCs with structures of ITO/SnO2/CsPbI2Br/poly(3-hexylthiophene)(P3HT)/Ag and ITO/SnO2/CsPbI2Br/carbon,achieving efficiencies of 12.22%and 10.44%,respectively.Such low-cost,high-efficiency all inorganic PSCs by using P3HT hole transport material or carbon-based structure without hole transport layer show the potential industrial application.(2)The vacuum-deposited PbI2 film reacts with the MAI/IPA solution to form a MAPbI3 perovskite film,and then a planar structure PSC was assembled for optimization based on C60 electronic transport layer.The optimal performance of MAPbI3 PSC was obtained via precisely controlling the reaction time of PbI2 film with MAI/IPA solution(10 min)and the addition of DMF in the MAI/IPA solution(1.0%,Volume ratio).As a result,an efficiency of 14.17%can be acheived.Series characterization results indicate that DMF in the MAI/IPA solution can promote the interaction between MAI and PbI2,and at the same time can also improve the surface morphology of perovskite thin films,thus enhancing the charge transfer at the interface and reducing the electron hole recombination.Finally,the 2T all-perovskite tandem devices base on the construction of ITO/SnO2/CsPbI2Br/P3HT/MoO3/Cu/Ag/C60/MAPbl3/Spiro-OMeTAD/Ag was prepared successfully with an open circuit voltage of 1.82 V.