The Study Of Interface Modification For All-inorganic Perovskite Solar Cells

All-inorganic perovskite solar cells（PSCs）have received extensive attention due to their superb thermal stability.Their power conversion efficiencies（PCEs）have been rapidly increased from the initial 2.9%to the current 20.37%.However,the defect states at grain boundaries and on the surface of the perovskite films are detrimental to photovoltaic performance and long-term durability of all-inorganic PSCs.Inferface modification has been proved to be an effective approach to passivate the surface defects of the perovskite films,which minimizes nonradiative recombination loss and thus improves the performance of solar cell devices.In view of the problem of low photocurrent and open-circuit voltage(V_oc)in all-inorganic CsPbIBr₂PSCs,an organic dye molecule namely VG1-C8 is introduced as an interface modification layer between perovskite and spiro-OMeTAD hole-transport layer（HTL）.The multiple Lewis base groups in VG1-C8（i.e.carbonyl and squaraine moieties）can effectively neutralize the positively charged defects on the perovskite surface.Meanwhile,the incorporation of VG1-C8 results in better energy level alignment at perovskite/HTL interface.Most importantly,theπ-conjugated dye molecule can extract holes directly from the perovskite absorber and promotes charge transport to the HTL.Consequently,the VG1-C8-treated devices show markedly improved V_ocand photocurrent density values,and thus an overall PCE of 12.10%.To our knowledge,this is the record efficiency reported so far for CsPbIBr₂PSCs.Thus,the present work demonstrates an effective interfacial passivation strategy for the development of highly efficient CsPbIBr₂PSCs.To solve the issues of surface defects and serious carrier recombination in inverted（p-i-n）all-inorganic CsPbI₂Br PSCs,low-temperature solution-processed sodium copper chlorophyll（SCC）interfacial layer is incorporated between the HTL NiO_xand perovskite.The carboxyl moiety in SCC can effectively passivate uncoordinated Pb²⁺ion defects on the perovskite surface.At the same time,the introduction of SCC interlayer is able to retard the crystaliztion process of perovskite,and thus results in high quality perovskite films.As such,the SCC treatment dramatically boosts V_ocfrom 1.04 V to 1.22 V,mainly because of the reduced nonradiative recombination at HTL/perovskite interface.The SCC-modified PSCs altimately afford a maximum PCE of 12.98%,which is much higher than that of the control devices（9.51%）.Moreover,the SCC-treated devices also exhibited excellent long-term stability under ambient condition.This work offers a promissing solution for the development of efficient and stable inverted all-inorganic CsPbI₂Br PSCs.