| Organic-inorganic hybrid perovskite materials have achieved rapid development in photovoltaics,while their volatile organic cations spontaneously deprotonate under the conditions of light and heat,resulting in the instabilities of perovskites.Thus,allinorganic perovskites without volatile components are highly desired to make up for those shortcomings.Among them,CsPbI3 with both a high melting point and a proper bandgap is considered one of the most promising candidates for photovoltaic applications.However,the imperfect Goldschmidt tolerance factor determines that black phase CsPbI3 has inferior stability,which would transit into non-photoactive yellow phase at room temperature.In view of the internal and external factors resulting in the phase transition,herein,we improved the stability of black phase CsPbI3 by regulating their growth process and the interface properties to prevent their(PbI6)4octahedra distortion.As a result,we fabricated all-inorganic perovskite solar cells(PSCs)and modules which show both high efficiencies and long-term stabilities.(1)The phase stability of CsPbI3 can be enhanced by adjusting the surface energy of perovskite crystals.Using a novel ligand,1-amantadine(ADMA),which can strongly interact with CsPbI3 and produce steric hindrance,we prepared stable quasiquantum dot(QQD)CsPbI3 films with high surface energy by one-step solution method.The QQD-based PSCs maintained 90%of their initial power conversion efficiencies(PCEs)after storage either in ambient condition for 30 days or 85℃heating for 336 h.Moreover,we used a single-step solution process to prepare a gradient grain-sized(GGS)CsPbI3 bilayer with gradient surface energy,which formed with the migration of ADMA ligand under preheating.This strategy not only suppressed the phase transition of CsPbI3,but also enhanced the carrier transport properties of perovskite films.The PSC based on the GGS CsPbI3 bilayer obtained a PCE of 15.48%and retained 85%of its initial PCE after 1000 h in air.(2)The phase reversibility of the high-temperature-processed CsPbI3 is utilized to improve its phase stability.A simple soft template-controlled growth(STCG)method was proposed to prepare high-quality CsPbI3 thin films at high temperatures.As the soft template molecule,ADMA significantly increased the nucleation rate of CsPbI3 films and gradually released the growth space of CsPbI3 with its volatilization.As a result,the high-quality CsPbI3 films were prepared under 350℃ with reduced defect-induced carrier recombination.The resultant champion device showed a PCE of 16.04%.In addition,an all-inorganic solar cell with the structure of FTO/NiOx/STCG-CsPbI3/ZnO/ITO was successfully fabricated,which retained 90%of its initial performance after 3000 h of continuous illumination and heating.(3)A hydrophobic CI-TTIN-2F hole transport material(HTM)with D-π-A structure was designed to stabilize the black phase CsPbI3 film.The undoped CI-TTIN2F HTM exhibited excellent photoelectric properties and hole transport properties due to the intramolecular charge transfer and intermolecular dipole interaction.Moreover,joint theoretical and experimental results indicated that multiple heteroatoms(such as N,O,S,and F)in CI-TTIN-2F HTM showed a significant multisite passivation effect on the surface defects of CsPbI3 films,which effectively reduced the defect density at the interface and the non-radiative carrier recombination.The resultant device achieved a PCE of 15.9%and maintained 86%of the initial PCE after storage in air for 1000 h.In addition,the CI-TIN-2F-based all-inorganic perovskite solar module achieved a PCE of 11.0%with an active area of 27 cm2.(4)We developed efficient electron transport materials(ETMs)and passivation layers in organic-inorganic hybrid perovskite devices and further optimized them for highly efficient and stable all-inorganic perovskite solar modules.Firstly,a novel single-crystalline TiO2 nanoparticle with high conductivity was developed as the electron transport material and o-PDEAI2 was designed as the passivator to prevent the formation of two-dimensional/three-dimensional(2D/3D)structure and promote the passivation effect.Based on this,we designed 4FPDMAI2 to form 2D/3D heterojunction in the CsPbI3 system to improve their phase stability and the PCEs of the device to 20.13%.Most importantly,we realized an efficiency of 24%for organicinorganic hybrid PSCs(0.088 cm2,certified by Newport),a world-record PCE of 22.72%for organic-inorganic hybrid perovskite solar modules(23.904 cm2,certified by the Institute of Electrical Engineering of Chinese Academy of Sciences),and the worldrecord PCE of 16.03%for all-inorganic perovskite solar modules(27.34 cm2,certified by the Photovoltaic Laboratory of the Institute of Micro Technique,Neuchatel,Switzerland).The encapsulated all-inorganic perovskite solar modules maintained 94%of the initial PCE after storage in ambient air with a relative humidity of～55%for more than 1500 hours. |
