All-inorganic Perovskite Solar Cells Based On Nanocrystaline Semiconductor Interfacial Materials

Beginning with 3.8%,organic-inorganic hybrid perovskite solar cells（PSCs）have achieved tremendous development in recent years and their certified power conversion efficiencies（PCEs）have already reached 25.7%.Although the efficiency of PSC has reached the standard of industrialization,the stability,especially the thermal stability and operation stability,needs to be further strengthened.Factors affecting the instability of PSCs mainly include:（1）Volatilization of the organic components in organic-inorganic hybrid perovskites,especially for methylammonium lead triiodide（MAPb I₃）.（2）The degradation of the organic charge-transporting layers.（3）Reactions between the commonly used metal electrodes and halogens from the perovskites during prolonged operation.In this thesis,in view of the instability factors in PSCs,we have exploited inorganic nanocrystalline semiconductor interface materials and halogen-resistant electrode to strengthen the stability of PSCs.（1）Uniform and dense NiO nanocrystalline films were obtained on CsPbI₂Br perovskite layers by spin-coating followed by thermal annealing in a protective N₂atmosphere.The Ni O nanocrystalline films exhibited adequate electrical conductivity and well-matched band structure with perovskite active layer,which enabled the fabricated all-layer-inorganic PSCs with the configuration of fluorine-doped tin oxide（FTO）/Nb-doped Ti O₂/CsPbI₂Br/tailored Ni O/Au to achieve a large V_OCof 1.26 V and a PCE of 15.14%.The all-inorganic PSCs based on tailored Ni O hole-transporting layer（HTL）shown better thermal stability:retained 85%of their initial PCEs after a thermal treatment at 85℃ in the dark in a nitrogen atmosphere with encapsulation for 1000 h,greatly surpassing the performance of the PSCs based on the organic HTLs（41%）.（2）A general strategy has been proposed to assemble high-quality metal oxide（C-MO_X）charge-transporting layers（CTLs）on top of the inorganic perovskite of CsPbI₂Br.Obtained C-MO_X CTLs present uniform and dense morphologies.The conductivities of metal oxide nanocrystalline films were improved and well-matched band structure with CsPbI₂Br perovskite layer were optimized by adjusting annealing conditions and the metal oxide types,respectively.The PCE of inverted CsPbI₂Br-based PSC based on C-Ti O₂ CTL has reached 14.0%.All-layer-inorganic PSCs based on C-Ti O₂,C-In₂O₃and C-Sn O₂CTLs shown good stabilities:<10%decline at 85℃ in the dark and<8%decline under continuous illumination at 45℃ for 1000 h.（3）Based on the second work,Nb is doped into the TiO₂ to improve the conductivity of the obtained CTL,and halogen-resistant Sb electrode has been introduced in an all-layer-inorganic inverted PSC with the configuration of FTO/Ni Mg Li O/CsPbI₂Br/C-Nb:Ti O₂/Sb,substituting commonly used Au,Ag and Cu electrode.The as-constructed all-layer-inorganic PSCs yielded a PCE as high as 14.8%and 14.4%with an active area of0.09 cm² and 1cm²,respectively.The fabricated devices based on Sb electrode achieved long-term stability:less than 6%PCE reduction and less than 10%PCE loss when under thermal stress（85℃,dark）and light-soaking tests（60℃,MPP tracking）for 1000 h,dramatically surpassing the performance of the devices based on commonly used Ag and Cu electrode.（4）A general strategy to prepare high-quality inorganic ETLs on top of inorganic perovskites at low temperature is proposed.It is interesting that these NC layers can be obtained by spin-coating followed by a simple ligand exchange in the anhydrous ether solution containing 1,2-ethanedithiol（EDT）.The obtained films exhibited dense,uniform morphologies and excellent charge-extraction capabilities.Well-matched band structure with CsPbI₂Br perovskite layer were optimized by adjusting the metal sulfides types.The as-constructed all-layer-inorganic PSCs with the configuration of FTO/Ni Mg Li O/CsPbI₂Br/E-Cd S/Au yielded a PCE as high as 15.04%and 14.42%with an active area of 0.09 cm² and 1cm²,respectively.Unencapsulated all-layer-inorganic PSCs based on E-Cd S present long-term stability:<9%decline at 85℃ in the dark and<8%decline under continuous illumination at 45℃ for 480 h.