The Research Of Molecular Engineering Strategies For High-performance Of Inverted Perovskite Solar Cells

Metal halide perovskites have attracted intensive research attention due to their unique optoelectronic properties,such as superior light absorption coefficient,high charge mobility,and long charge diffusion length.The power conversion efficiency(PCE)of single-junction perovskite solar cells(PSCs)has recently reached a certified value of 25.7%,approaching the performance level of crystalline silicon(c-Si)solar cells.However,the device stability of PSCs presents a significant obstacle to truly commercializing PSCs.Due to the high density of trap states in polycrystalline perovskite films,recombination may occur either in bulk or close to the interface of adjacent charge transport layers.The intrinsically weak bonding of halide perovskite materials,such as fast ions migration(I~-)and volatile properties of organic cations,usually leads to the degradation of perovskite-based optoelectronics.The defects may also appear on the transport layers and cause recombination across the interface between charges transport and perovskite layers,resulting in transport resistance and degradation of devices.Besides,lead toxicity in the perovskite light absorbers restricts the perovskite photovoltaic application in the real world.Here,muti-functional materials are applied to modify the contact interface between each functional layer,to achieve highly efficient and stable inverted PSCs.The content is as follows:(i)Design and fabrication of organic/inorganic bi-layer hole transport layer(HTL).Using a p-type semiconductor TPA-BA(4,4’’-bis(diphenylamine)-[1,1’:3’,1’’-terphenyl]-5’-carboxylic acid)to modify the NiO_x/perovskite interface to form a bi-layer HTL based on NiO_x.TPA-BA can anchor on the NiO_x surface and facilitate the hole transfer between the perovskite and NiO_x layer by minimizing the interfacial band energy offset.Furthermore,with the protection of TPA-BA,chemical reactivity at the NiO_x/perovskite interface is reduced,which would otherwise lead to detrimental perovskite degradation.These translate into a champion device with a PCE of 22.2%for an active area of 0.1225 cm~2.The modified PSCs retained over 90%of their initial efficiencies after 1000 h continuous operation under1 sun illumination and thermal aging at 85℃,respectively.(ii)Regulation of perovskite absorber layer and interface of HTL.Using a multifunctional dye molecule 2-cyano-3-(4-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)phenyl)acrylic acid(BT-T)to modify the active perovskite layer,which is also a p-type semiconductor.Computation and experimental investigations reveal that the cyanoacrylic acid group of this modifier might be anchored onto NiO_x and perovskites via similar metal ion coordination,increasing the interfacial contact.BT-T can be anchored on the NiO_x surfaces with partial proton transfer from BT-T to NiO_x,reducing the energy loss from 0.39 eV to 0.33 eV and improving interfacial charge transfer at the buried interface.Besides that,BT-T improves the crystallization of perovskite films,enlarges the grain size,and passives deep defects on the surface and GBs of the perovskite films.Correspondingly,inverted PSCs achieved champion efficiencies of 22.2%for active areas of 1.01 cm~2.The high-performance devices retained over 90%of their initial efficiencies after continuous operation under one sun illumination and the thermal test.(iii)Design and fabrication of anti-corrosion and multifunctional metal electrodes.Design and synthesize multifunctional copolymer-PDMEA(2-((2-methyl-3-(2-((2-methylbutanoyl)oxy)ethoxy)-3-oxopropyl)thio)-3-(methylthio)succinic acid),and using it to modify the surface of metal and form Ag/PDMEA complex electrode.The high density of thioether/carboxyl functional groups present in PDMEA allows the Lewis acid-base reaction between PDMEA and Polyethyleneimine to improve the interfacial bonding between the ETL and electrode interface.A transferring and laminating approach was utilized to replace conventional thermal or E-beam deposition for the fabrication of metal electrodes.Meanwhile,PDMEA provides sites for metal ion coordination and immobilization that effectively inhibits the redox reactions between Ag and iodides and the leakage of toxic Pb.The resultant PSC achieved a PCE of 22.68%with an active area of 1cm~2,the devices without encapsulation retained over 90%of their initial efficiency after 85℃ aging for 3000 h.