Two-dimensional Perovskite Is Applied To Optimize The P-type Interface Of Invert Perovskite Solar Cells Prepared Via A Two-step Method

Organic-inorganic hybrid perovskite solar cells with efficiencies of exceeding 25percent show great promise for commercialization and are the most promising candidates for next generation photovoltaic products.Invert-structure perovskite solar cells(PSCs)have the advantages of good stability,low hysteresis effect and can be used in flexible devices and tandem devices.However,in the high performance invert structure PSCs reported so far,most perovskite films are treated by a one-step process.Although the two-step sequential deposition method has been considered to be more reproducibility and easier to prepare perovskite films,the PCE of Invert-PSCs prepared by the two-step sequential deposition method still lags far behind that of the one-step method.This is partly due to the poor wettability of lead halide solution to Poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)and other hole transport materials,resulting in poor surface coverage and uniformity of perovskite films.On the other hand,the control of lead halide-solvent mesophones and their micro-and nano-structures remains a challenge resulting in rapid and uncontrolled reactions between sequentially deposited organic components and predeposited lead halides.The resulting low-quality perovskite films often lead to deep-level defects in PSCs and non-radiative recombination during carrier transport,resulting in degraded device performance and accelerated device aging.Existing strategies such as precursor additive engineering,solvent annealing,and surface passivation have been reported to optimize the two-step preparation of invert PSCs.However,few studies have focused on improving the performance of Invert-PSCs by optimizing the buried interface(P-type interface)of Invert-PSCs.We first investigated the mechanism of the influence of TEAI(2-thiophene ethylamine iodide)on the quality of perovskite films and device properties by introducing TEAI(2-thiophene ethylamine iodide)at different positions in the two-step process.When TEAI is introduced in the first step,the formation of an intermediate phase associated with TEA~+promotes the preferential directional growth of n≥3 quasi-two-dimensional perovskite(Q-2D).The enhanced electron-phonon coupling in quasi-two-dimensional perovskite prolongs the carrier recombination lifetime and ensures efficient charge extraction.Compared with the corresponding three-dimensional device,the invert-device achieves 21.01%efficiency and improves the repeatability of the experiment.This work highlights the relationship between the phase structure and physical properties of quasi-two-dimensional perovskites and provides a general phase engineering method to regulate their applications in optoelectronic devices.Secondly,carrier diffusion in the perovskite layer is long enough,and non-radiative recombination usually occurs at the interface and buried interface of the perovskite.We adopted a method of introducing a kind of more robust two dimensional perovskite into the P-type interface of invert-perovskite solar cells to optimize the interface.A 5nm thick layer of lead iodide was thermally vaporized on the hole transport layer,and a layer of VBAI(4-vinylbenzylamine iodide)was coated on it,and then crosslinked by ultraviolet lamp to form a two-dimensional perovskite with covalent bond quantum well structure.The optimized interface corresponding devices show a low non-radiative recombination,and obtain an open-circuit voltage of 1.15V and a photoelectric conversion efficiency of 23.02%.The problem that the optimization layer of Invert-PSCs interface is easily dissolved by the upper precursor solution is overcome.This work provides an innovative approach to optimize the P-type interface of invert PSCs.