Preparation Of SnO₂ And Pbs Nanomaterials And Their Applications In Low-Temperature Perovskite Solar Cells

Since Since the advent of perovskite solar cells?PSCs?in 2009,the photoelectric conversion efficiency?PCE?has increased from 3.8%to 24.2%certified by NRELduring the past decade.Efficient PSCs are inseparable from the excellent electron transport layer?ETL?and hole transport layer?HTL?.This article explores more excellent ETL and HTL materials to improve the performance of PSCs in three different directions.In this paper,all devices are prepared under low temperature conditions.The main research contents and results are as follows:?1?The yttrium doped tin dioxide?Y-SnO₂?nanorods were synthesized by solvothermal method,which was applied to PSCs as low temperature ETL?150??.TEM characterization show that the Y doping makes the SnO₂ nanorods more regular and tend to be self-organized and ordered which can help tofabricate continuous and dense ETLs.The XPS characterization indicate that Y was incorporated into the SnO₂ lattice with Y³⁺.Tests such as UV-vis and UPS show that,compared to SnO₂,the band gap of Y-SnO₂ becomes wider,the conduction band moves up,and more matched with perovskite,which facilitates the transmission of electrons.Tests such as Tafel,PL,TRPL,and dark I-V curves can indicate that Y-SnO₂ has better conductivity,faster electron extraction rate,and lower recombination than SnO₂.PSCs based on low temperature Y-SnO₂ have better performance,whose average PCE is 20.11±0.30%,and the highest PCE is up to20.71%?20.09%?when scan by reverse?forward?direction of voltage.?2?Based on the existing work,mesoporous PSCs with low temperature SnO₂-based were prepared,which can solve the high temperature sintering problem in mesoporous layer.SnO₂ nanorods synthesized by solvothermal method were self-assembled into SnO₂ emulsified microspheres?SnO₂ EMs?through ultrasonic emulsification method and used as mesoporous layers.SnO₂ EMs were stripped their organic ligand in situ by feat of NOBF₄ solution without destroying the structure.The TEM tests show that the SnO₂ emulsified microspheres are composed of SnO₂nanorods,and there are many voids inside,which make them be qualified on mesoporous materials.The top view SEM images of the SnO₂ emulsified microspheres show that the NOBF₄ solution treating has little impact on the assembled microspheres'spherical structure.The mean PCE of mesoporous PSCs based on BF₄^--capped SnO₂ EMs is 19.94±0.23%andthe highest PCE of the devices can reach 20.42%?19.72%?with the scan of reverse?forward?direction about voltage and the champion fill factor is as high as 79.70%.When PSCs was in continuous output withbia voltage of 0.948 V corresponding to P_max,the mesoporous PSCs based on BF₄^--capped SnO₂ EMs can obtain a stable current of 20.31 mA cm^-2and a PCE of 19.26%.?3?The p-type semi-conducting PbS nanocrystals were prepared by hydrothermal method,which can replace the traditional Li-TFSI and tBP double dopants,and combined with undoped Spiro-OMeTAD as HTL to prepare PSCs.Due to the hydrophobic properties of PbS,the contact angle of water on the surface of PbS/spiro composite HTL is much larger than that of traditional spiro,which is beneficial to acquie the long-term stability of the device.The UV-vis and UPS tests show that the valence band of the PbS/spiro composite HTL is shifted from-5.20 eV to-5.99 eV compared with the traditional spiro,which match the valence band of the perovskite and improve the transport of holes.Tests show that PbS/spiro HTL has greater conductivity and stronger hole extraction ability.Deviceswith PbS/spiro HTLs have smaller defect state density and interface charge loss.The PSCs based on0.04%PbS/spiro composite HTL can obtain a PCE of reverse?positive?18.98%?17.82%?.The reverse PCE increased by 44.12%compared to that of undoped spiro PSCs PCE of 13.17%.Compared with the double-dopant non-oxidized traditional spiro HTL PSCs 17.49%PCE,which were increased by 8.56%.Without any encapsulation in an air environment for 300 h,,the device with 0.04%PbS/spiro composite HTL still maintained 83.4%of the initial PCE which was mainly due to the hydrophobicity of PbS.