Ionic Liquids Assist Fabricating High-efficiency And Stability Flexible Perovskite Solar Cells

With the unremitting development of intelligent electronic devices and information technologies,the integration of flexible electronics and textiles into wearable electronics has entered people’s daily lives.To ensure these wearable electronic devices could operate normally,mobile power supplies with matching stable output are necessary.Flexible wearable perovskite solar cells have unique advantages of lightweight,portability,flexibility,comfort,high efficiency,and stability,which are in accordance with ergonomic design,and they have attracted much public attention,becoming one of the most anticipated photovoltaic products.However,intrinsic flaws and mismatches in contact with ETL in perovskite films have a significant impact on PSCs PCE and stability.ILs are being used to address the mismatch interfaces with ETL and internal flaws of perovskite films,enhancing perovskite film quality,charge carrier extraction and separation,and thus boosting PSC PCE and stability.Meanwhile,a simple strategy was applied to build ff-PSCs in order to study their stability,providing a novel concept for the future development of the flexible wearable power supply.The main contents are as follows:（1）ILs show high conductivity,excellent electrochemical stability,and unique advantages in passivating interfacial defects.Hence,we introduced BMIMHSO₄ IL into the Ti O₂/MAPb I₃ interface.The results show that BMIMHSO₄ can regulate the surface electronic properties of Ti O₂ ETL to form oriented permanent dipoles,reduce the work function,improve electron mobility and conductivity,and promote interfacial charge transfer efficiently.Additionally,the homogeneous distribution of IL provides abundant nucleation sites for perovskite crystallization,as do the N-C=N groups of BMIM⁺cations and the S=O groups of HSO₄^-anion.They could passivate the defects at the interface by coordinating with Pb to induce perovskite crystal vertical growth.This dual-interfacial modification enabled PSCs fabricated in open air to attain a maximum PCE of 19.13%.Furthermore,the devices were exposed without encapsulation in a dark,open-air environment with a RH of 40±2%and a temperature of 25±5°C.After 600 h,the residual PCE is at its original value of 90%.（2）We introduced[AOEMIM][BF₄]into the perovskite precursor solution because it remains at the surface and grain boundaries during perovskite annealing owing to the very low vapor pressure.The findings show that in a perovskite film,the[AOEMIM]⁺cation is composed of C=O groups that form a C=O?Pb coordinate bond with uncoordinated Pb²⁺.While the inclusion of BF₄^-increases the perovskite film’s hydrophobicity.The dual role of zwitter ions reduces defect state density while inhibiting non-radiative recombination,dramatically improving perovskite film quality and device performance.The highest PCE for the gadget is 19.86%.The devices retain 93%and 89%of their original efficiency after 30 and 10 days of exposure in an open-air environment at 80±2%RH and 85°C,respectively.（3）The BMIMHSO₄ and[AOEMIM][BF₄]IL are applied together to fabricate flexible perovskite solar cells.Furthermore,ff-PSCs were constructed by connecting the top Ag electrode and Cu foil through physical bonding and overlaying the fabric.The results show that the crystallization and internal carrier dynamics of perovskite films on ITO/PEN flexible substrates can be improved by the synergistic action of the two kinds of ILs,achieving the highest PCE of 14.17%for flexible perovskite solar cells.The maximum efficiency of the ff-PSCs was 12.24%.The acrylic tape not only plays the role of physical bonding,but more importantly,it has the role of packing batteries,improving moisture insensitivity.After these devices were continuously irradiated,At 100 m W/cm² illumination intensity for 240 min,the ff-PSCs maintain80%of their original efficiency.After 10 days at room temperature,the efficiency of the ff-PSCs barely decreased（maintaining 99%of the initial value）.The PCE of ff-PSCs and f PSCs maintained 50%and 70%of the original value,respectively,after80 times at a curvature radius of 3 mm.And the PCE of ff-PSCs and f PSCs maintained 25%and 55%of the original values,respectively,after continuous bending for 30 times at a smaller curvature radius of 1.5 mm.