Study On Perovskite Solar Cells For Four-terminal Silicon Tandem Solar Cells

In recent years,solar cells have been rapid development due to their capacity which can convert solar energy into electricity with the development of our society.Thereinto,as the mainstream product of the photovoltaic market,silicon solar cells with PCE exceeding 26%is an approach to its theoretical limit of 29.4% and is difficult to further growth.Therefore,PSCs have attracted much attention in past few years due to their excellent optoelectronic characteristics,such as simple process,low-cost,high-absorption,long carrier diffusion length and adjustable band-gap,and the corresponding PCE have increased rapidly from 3.8%in 2009 to exceed 25% today.However,on account of its mature industrialization technology,the silicon solar cell occupies more than 90% of the market share.Hence,it is still impractical for PSCs to replace silicon solar cells in the market completely near-term.Fortunately,the feature of adjustable band-gap makes PSCs one of the most promising candidates to combine with silicon solar cells for tandem solar cells.This tends to continue the life and breaks the S-Q limit of silicon solar cells.In addition,mature industrialization technology of silicon solar cells means that preparation technology for high-performance and stability PSCs is the key point for excellent perovskite/silicon tandem solar cells.In this paper,we will devote ourselves to the fabrication of high-efficiency top SPSCs via properties optimization of the film,PSCs barrier layer and TOC preparation method,and realizing the development of a perovskite/silicon tandem solar cell process.The details are as follows:（1）The performance of PSCs has improved with the tuning of MA/FA and Br/I components in precursor mixed solution in this work.We show that the halide composition in mixed PSCs could greatly affect the J-V hysteresis and PCE.The results show that the halide ratio is essential for the formation of high-quality perovskite film with a longer radiative carrier recombination lifetime,uniform crystal size,and better surface morphology.By changing the cation/anion composition,the PSC based on 18% Br shows the negligible J-V hysteresis（HI of 0.006）and the enhanced PCE（17.41%）.The statistics result also shows that the devices with 18% Br have a smaller discreteness in the device performance.（2）In this work,we demonstrate a facile way to improve the quality of perovskite film by a regrowth process via using the DMF/CB mixed solution to post-treat the perovskite film.By using the regrowth method,XRD measurement shows that the crystal quality of the perovskite film is improved,SEM results demonstrate that the perovskite material shows a relatively uniform grain size and the electrical impedance spectroscopy measurement shows that the recombination is lowered.The photoluminescence spectra measurement also shows that the optimal perovskite film has a long carrier lifetime compared to the control film.The corresponding efficiency of perovskite solar cells with the construction of ITO/Ni Ox/MA0.7FA0.3Pb I3-x Clx/PCBM/BCP/Ag is improved from 16.33% to 18.21% owing to the optimal perovskite film.Finally,stability of the PSCs is also improved with the introduction of the regrowth process.（3）Here,we demonstrate a facile strategy that can carry out double passivation to improve the performance of PSCs.By using the dilute halide salt PEABr solution to treat the perovskite film,SEM and XRD measurements suggested that Pb I2 is precipitate from the perovskite during the post-annealing process.Both PEABr and Pb I2 can passivate the perovskite film and by combining PEABr and Pb I2,the double passivation improves the performance of PSCs significantly.Very high short circuit current density of 24.30 m A/cm2,open-circuit voltage of 1.10 V and fill factor of 79.75% is achieved which leads to a surprising efficiency of 21.32% for the passivated device.The improved efficiency is mainly according to available surface passivation of the perovskite material,leading to repressed non-radiative recombination and unhindered charge collection.In addition,the passivated device exhibits better PCE stability relative to the control device.The treated device could maintain 93.00% of its initial PCE in 85℃ for 60 min which is higher than 83.57% of the control device.（4）In this work,we investigated the effect of oxide interlayer for perovskite solar cell,and an inorganic aluminum-doped zinc oxide（AZO）interlayer is inserted between the PCBM layer and the metal electrode so that electrons can be collected efficiently by the electrode.It is shown that with the help of the PCBM/AZO bilayer,the power conversion efficiency of PSCs is significantly improved to 16.19%.Towever,This efficiency is too low to fabricate high-performance perovskite/silicon tandem solar cells.Hence,an ultra-wide bandgap semiconductor material of Ga₂O₃ is introduced between FTO and Sn O2 to regulate the interfacial charge dynamics by forming the Ga₂O₃/ Sn O2 electron-transporting bilayer.Ga₂O₃ has an appropriate conduction band minimum（CBM）which benefits the electron transport,and at the same time,it has a very deep valence band maximum（VBM）which could be regarded as an effective blocking layer.Such innovative structure triggers the advantages of a lower work function and a smoother surface of the electron transporting bilayer which leads to a high-quality perovskite film.Furthermore,superior hole-blocking properties of the introduced Ga₂O₃ layer could effectively reduce the interfacial recombination.All the properties could help to improve the extracting and transporting ability of charge carriers synergistically.Finally,PCE of the device with Ga₂O₃ layer is achieved 21.56% and maintained its 92.29% initial PCE after store in atmosphere condition for 1000 h.（5）In this study,we fabricated the tandem solar cell based above research resultd,developed high-transmittance and high-conductivity transparent conductive oxide by sputter technology and the test results demonstrate that the average transmittance of the DC sputtering IZO is around 80% and its sheet resistance is only 20.7 Ω/□.Meanwhile,AZO and Mo Ox are used as buffer layers in p-i-n and n-i-p structure semitransparent perovskite solar cells to impair the damage of perovskite film during the transparent conductive oxide sputtering process.Ultimately,with the assistance of silver grid line,high-performance semitransparent perovskite solar cell assumes an efficiency of 20.85% is prepared and corresponding four-terminal tandem perovskite/silicon solar cell also obtained satisfactory power conversion efficiency of 29.33% and certified efficiency of 28.42%.