Regulation of Low-dose Stannous Iso-octanoate for Two-step Prepared Sn-Pb Alloyed Perovskite Solar Cells
In the preparation of Sn-Pb alloyed perovskite,a large amount of stannous fluoride(SnF2)additive is often employed to inhibit the oxidation of Sn2+ions.However,excessive SnF2 deteriorates quality of the film,photoelectric conversion efficiency(PCE)and stability of the device.Therefore,the development of new antioxidants at low doses is essential to achieve high-performance Sn-Pb alloyed perovskite solar cells.In this study,a two-step process was used to prepare Sn-Pb alloyed perovskite film.In the first step,low-dose stannous iso-octanoate(SnOct2)was introduced to replace SnF2 to inhibit the oxidation of Sn2+.This study showed that the additive could improve the crystallization quality of the film,and the average grain size of the film with SnOct2 could reach 850 nm while the amount of grain boundaries was reduced.The film with the addition of SnOct2 still contained 93.5％Sn2+after storage for 7 d in the glove box.And due to the excellent oxidation resistance of SnOct2,the device with the additional SnOct2 had a lower defect state density,which was reduced from 7.20× 1015 to 4.74×1015cm 3,inhibiting the non-radiative recombination.In addition,SnOct2 improved the surface energy levels of perovskite films.Finally,PCE of Sn-Pb alloyed perovskite cell supplemented with 0.030 mmol SnOct2 reached 17.25％,superior to that of device supplemented with 0.10 mmol SnF2(11.63％).After storage in nitrogen for 50 d,more than 70％of initial PCE was still preserved.
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