Efficient And Stable Inverted CsPbI₃ Inorganic Perovakite Solar Cells And Their Air Fabrication

Perovskite solar cells（PSCs）have been widely accepted as the promosing commercialization for their excellent photoelectric properties and low-temperature solutionable fabrication.Their certified efficiency has been brokento 25.7%.However,their thermal and operational stability are seriously limited by volatile organic components.Substituting organic cations by inorganic Cs⁺to form all-inorganic Cs Pb X3（X=I,Br,Cl）can resolve the instable chemical intrinces.Focused on the crystallization and non-radiative recombination issues,researchers have proposed many strategies and realized high efficiency over 20%based on regular structure.The regular structure is mismatched to the promising application of tandem photovoltaic.Also,the undesirable dopants in HTLs seriously hinder the thermal and moisture tolerance of the devices.In comparison,the inverted structure（p-i-n）can remove these limitations.Unfortunately,inverted inorganic PSCs are far-lagged.In parallel,low-cost air fabrication of inorganic PSCs also gets numerous attentions.But the water-induced phase transition and inferior crystallization lay a huge obstacles for their progress,and air-fabrications inverted is still vacant.In this article,we have conducted 4 works to solve the crystallization,trap formation,phase stability and obstacles on air fabrication for high-performance inverted CsPbI3 PSCs.（1）We adapted MAPy A as the post treatment to realize the in-situ healing and stabilizing on the CsPbI3 films.The efficiency and stability of the inverted CsPbI3PSCs got great promotions.When heated as 100°C,MAPy A would be decomposited into MA gas and Py A solid.The MA gas could heal the non-dense morphology and traps for better crystallization.Whereas the Py A at GBs and surface could passivate the defect and inhibit the phase transition.As a result,the inverted CsPbI3 PSCs revealed a champion efficiency of 16.67%with good stability.Unpackaged devices remained>80%after operated at ambient condition for 1800 min.（2）The Si-Cl was incorporated into precursor as the desiccant and stabilizer for humidity-assisted chlorination and protection in the air-fabricated inverted CsPbI3PSCs.As the rapidly hydrolyzed molecules,Si-Cl could consume the water molecules for humidity-less atmosphere during air operations.In parallel,the hydrolysis production of HCl would chloride the CsPbI3 for better crystallization and phase stability.Also,the other production of Si-OH was polymerized at GBs,and effectively passivated the traps and insulated the external erosions.A champion efficiency of18.93%was realized based on the air-fabricated inverted CsPbI₃ PSCs.What’s more,the optimized device revealed no decay after MPP tracking at 65°C for 900 h.（3）MAAD was choused as the in-situ water-induced stabilizer with strong interaction to realize a wide operating humidity window for the air-fabricated CsPbI3PSCs.The MAAD was also the fast-hydrolysis molecule and reduced the water erosions during air fabrication.The hydrolyzed production of MAAC with two carboxyl groups would control the crystallization and suppress phase transition.Based on DFT simulations,MAAC features stronger strength on CsPbI3 surface than water,which would effectively insulate the water erosions for better moisture tolerance.The optimized devices could realize high efficiency（>18%）fabricated in the RH 0-60%.A high efficiency of 19.25%was achieved at RH 40%condition.The devices remained96.8%even operated at 65°C for 850 h.（4）The molecular construction of FBJ additives was proposed to regulate the trap formation in the air-fabricated CsPbI3 films.The phoelectrical properties and stability of CsPbI3 films were greatly improved,which resulted in the promotions of both the efficiency and stability of the inverted CsPbI3 PSCs.FBJ featured stronger adsorption strength on CsPbI3 surface than water,which could suppress trap formation for water erosions.In addition,FBJ with acylhydrazyl group could strongly interact to CsPbI3components,which increase the forming energy of various traps during natural crystallization.Moreover,the reductive acylhydrazyl would reduce the oxygen erosions for less VI traps.The resulted devices realized a champion efficiency of19.27%with high Voc of 1.225 V and good reproduction.The optimized device remained 97.47%after MPP at 60°C for 600 h.Our works have promoted the progress of the inverted inorganic CsPbI3 PSCs based on the regulations of trap formation,crystallization and phase stability of CsPbI3 and broken the highest efficiency for many times.Associaing the strategies for insulation of the water and oxygen erosions during air fabrication,we have realized the first air-fabricated inverted inorganic PSCs with impressive stability.Our works have layed the foundation for high-performance inorganic perovskite photovoltaics and the promising application in tandem solar cells.Despite of the progress made in this paper,the deep insights into the limitations and intrinces of inverted inorganic PSCs are still superficial.More detail researches on up-scalable fabrication and tandem structure are urgent need for future commercialization.