| Due to its excellent photoelectric properties such as low exciton binding energy,long carrier lifetime,and high defect tolerance,metal halide perovskite has shown great application prospects in the fields of solar cells,light emitting diodes,photodetectors,and lasers,and has received widespread attention.In recent years,the performance of perovskite solar cells(PSCs)has been rapidly improved,and the power conversion efficiency(PCE)has increased from initial 3.8%(2009)to 25.8%(2023).However,there is still much room for improvement in the efficiency of PSCs from theoretical limits,and the stability of devices is not ideal,which has become a bottleneck limiting the practical application.This is mainly due to the soft ion lattice characteristics of perovskite,which inevitably leads to defects in the crystal growth process of perovskite materials.Meanwhile,energy level mismatches between functional layers and interface defects in devices can have a negative impact on device performance.Based on this,this paper conducts research around additive engineering to optimize the performance of perovskite based devices,revealing the regulation of additive modification types and film preparation processes on the performance of perovskite optoelectronic devices.Through effective passivation of defect states in perovskite materials and devices,it can promote carrier transport and improve the efficiency and stability of perovskite optoelectronic devices.The specific work is as follows:(1)Improving the crystal quality of perovskite films and suppressing the generation of defect states are crucial for achieving high-performance PSCs.This work proposes to use potassium hexafluorophosphate(KPF6)as an additive to modify perovskite thin films.Through the strong coordination ability between PF6-and lead iodide(Pb I2),it compensates for halide vacancies formed during the crystallization process of the films and inhibits the generation of Pb 0 defects,thereby reducing the non-radiative recombination during the carrier transport and extraction processes in devices;At the same time,the introduction of KPF6 improves the crystal quality of perovskite films,increases the grain size of perovskite,and obtains perovskite films with single layer grains,promoting the longitudinal transfer of carriers;The passivation of perovskite film defects increases the PCE of the device from 18.99% to 22.04%,and the device T80 lifetime(efficiency reduced to 80% of the initial efficiency)is 4400 h.(2)Subsequently,aiming at the interface defects between the perovskite absorption layer and the transport layer in PSCs,λ-Carrageenan(λ-C)introduced as an additive to the interface of the electron transport layer(Sn O2)/perovskite layer,using the sulfate group of λ-C coordinates with Sn4+ of Sn O2 and Pb2+ in perovskite films simultaneously,effectively passivating interfacial defects and improving the conductivity of Sn O2 films;Meanwhile,due to the strong binding force between the sulfate group in the λ-C molecule and Pb I2 in the perovskite film causes λ-C molecules can effectively penetrate the interior of perovskite films and passivate internal defects in the films;The passivation of the above interface defects not only effectively inhibits the non-radiative recombination of the carrier transport and extraction processes,but also releases the interfacial stress and improves the stability of the perovskite film,the introduction of λ-C molecules also optimizes the arrangement of interfacial energy levels.Based on this,the efficiency of PSCs has been further improved to 23.81%,which is by far the highest efficiency of devices based on green natural molecular additives.Furthermore,the lifetime of device T80 has been increased to 5000 h.(3)Further,p-phenylenediamine iodide(PPDAI2)and carboxylic acid modified Fe3O4 magnetic nanoparticles(MNPs)as additives were introduced at the interface of perovskite film/hole transport layer(HTL),and the perovskite composite structure was constructed by combining magnetic field interaction.Relying on the interaction between NH4+ of PPDAI2 and COO-of Fe3O4 MNPs,magnetic force induced PPDA2+to achieve a top-down distribution at the grain boundary.By NH4+ of PPDAI2 to combine with Pb I2 in perovskite,2D perovskite was formed on the surface and grain boundary of 3D perovskite films,thereby constructing a 2D/3D composite structure;The 2D/3D structure not only passivates the interface defects of perovskite/HTL,but also promotes the vertical carriers transport,effectively inhibits the non-radiative recombination of carriers at the interface,thereby significantly improving the open circuit voltage(Voc)and fill factor(FF)of PSCs,increasing the PCE of PSCs to24.21%,and the device T80 lifetime to 6000 h;On this basis,the PCE of flexible devices reached 21.23%,which is the device based on 2D/3D perovskite flexible devices.(4)Based on the above work,the performance of Pe LEDs was further optimized using additive engineering strategies.The 3,3-diphenylpropylamine iodine(DPPAI),phenylethyl ammonium iodine(PEAI),and 1-naphthylmethylammonium iodine(NMAI),were simultaneously introduced into the perovskite film to prepare the quasi2 D perovskite film;By adjusting the ratio of DPPA+,PEA+,and NMA+ spacer cations,and adjusting the spatial distribution of crystal phases in quasi 2D perovskite films,the orderly distribution of crystal phases was achieved;The spatial distribution of crystalline phases in perovskite films,on the one hand,achieves continuous regulation of luminescence wavelengths from 628-664 nm,on the other hand,enhances carrier transfer efficiency and improves radiation recombination rate;Furthermore,the introduction of PVP at the interface between the HTL and perovskite layer improves the surface wettability of the HTL layer,thereby improving the crystal quality of the perovskite film;After modification,the pure red(636 nm)device achieve high external quantum efficiency(EQE)and maximum brightness of 18.2% and 1543 cd m-2respectively.This is the best pure red(620-640 nm)Pe LEDs fabricated based on quasi2 D perovskite films. |
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