The Optimization Of The Semitransparent Perovskite Solar Cell For The Application On The Tandem Solar Cell

As a rising star,perovskite materials with superior photovoltaic performance appear into the field of vision,recently.Due to its tunable bandgap,semi-transparent perovskite solar cells(ST-PSCs)are expected to be combined with crystalline silicon cells to form tandem solar cells(TSCs)to break the efficiency limit.ST-PSCs are usually composed of a charge transfer layer,a perovskite intrinsic layer,and a transparent electrode(TE),each of which is the key to determine their ultimate efficiency.Conventional titanium oxide(TiO₂)as an electron transport layer(ETL)in hybrid organic-inorganic perovskite solar cells requires a sintering process at a high temperature(>450?)to be crystalized,which is not suitable for flexible PSCs and TSCs with their low-temperature processed bottom cell.Here,we introduce a low-temperature solution method to deposit a TiO₂/tin oxide(Sn O₂)bilayer towards an efficient ETL.From the systematic measurements of optical and electronic properties,we demonstrate that the TiO₂/Sn O₂ ETL has an enhanced charge extraction ability and a suppressed carrier recombination at the ETL/perovskite interface,both of which are beneficial for photo-generated carrier separation and transport.As a result,PSCs with TiO₂/Sn O₂ bilayer ETLs present higher photovoltaic performance of the baseline cells compared with their TiO₂ and Sn O₂ single-layer ETL counterparts.The champion PSC has a power conversion efficiency(PCE)of19.11%with an open-circuit voltage(V_oc)of 1.15 V,a short-circuit current density(J_sc)of 22.77 m A/cm²,and a fill factor(FF)of 72.38%.Additionally,due to the suitable band alignment of the TiO₂/Sn O₂ ETL in the device,a high V_oc of 1.18 V is achieved.The transparent electrode(TE)is also a critical step from traditional PSC to ST-PSCs.Currently,the application of aluminum-doped zinc oxide(AZO)on the ST-PSC is seldom been reported,which is low cost,environmental friendliness and conducive to commercial production.Generally,AZO is deposited by magnetron sputtering to obtain excellent film performance.However,the deposition process will damage the perovskite and hole transport layer to hinder the ST-PSCs development.Herein,the AZO sputtered at room temperature with a low damage deposition process is adopted in semi-transparent PSCs.The AZO film shows a good photoelectric performance,with an average transmittance of above 83%and a sheet resistivity of28.08?/?at 60 W sputtering power.To avoid the ion bombardment,we insert a buffer layer and change the sputter parameter in the deposition process.The experimental results indicate that a buffer layer of molybdenum oxide(Mo O_x)(i.e.,15nm)can effectively protect the PSC,while the photovoltaic performance is improved by balancing the thickness and conductivity of the transparent electrode.Finally,the ST-PSC yields a champion PCE of 16.60%with a V_oc of 1.18 V,a J_sc of 20.57m A/cm² and an FF of 68.44%.In conclusion,based on the low temperature process,firstly,it has been proven that the TiO₂/Sn O₂ bilayer is a promising alternative ETL for high efficiency PSCs.The TiO₂/Sn O₂ ETL can significantly improve the V_oc of the devices,which is also important for the performance of the ST-PSCs.Secondly,the optimized AZO electrode is served as the rear electrode of the ST-PSCs,yielding high PCE illuminating from both front and back sides.Finally,combining this semitransparent PSC as the top cell,and a tunnel oxide passivated contact(TOPCon)silicon solar cell as the bottom cell,a four-terminal perovskite/Si TSC shows a high PCE of 23.07%.