Interface And Morphology Control Of P-i-n Perovskite Solar Cells

Organic-inorganic hybrid perovskite has the advantages of high absorption coefficient,flexible and adjustable band gap,long carrier life and carrier diffusion length.It is considered to be one of the most potential new generation solar cell materials and has attracted extensive attention.Since the first report of perovskite solar cells in 2009,the photoelectric conversion efficiency of perovskite solar cells has rapidly increased from 3.8%to 25.7%.Perovskite solar cells can be divided into two types according to device structure:n-i-p structure and p-i-n structure.Most perovskite solar cells with high photoelectric conversion efficiency are prepared based on n-i-p type structure.However,the preparation process of perovskite solar cells with this structure is more complex.In comparison,the preparation process of perovskite solar cells based on p-i-n structure is simpler,which can realize low-temperature solution processing and is compatible with flexible substrates.It also has obvious advantages for the preparation of large-area and laminated perovskite solar cells.In addition to the slightly lower photoelectric conversion efficiency of p-i-n structure perovskite solar cells,there are still some problems in the working mechanism of perovskite solar cells with this structure which need to be further studied.In order to further improve the performance of p-i-n perovskite solar cells and study the carrier dynamic process in the device,this paper focuses on the two key factors affecting their performance,interface and morphology.The specific research work is as follows:（1）Using discrete SnO₂ nanoparticle modified PEDOT:PSS to improve the photoelectric conversion efficiency of p-i-n perovskite solar cells.In this part of work,we focus on the problem that the electron in perovskite film is easy to diffuse to one side of PEDOT:PSS film due to the low LUMO level position of PEDOT:PSS film,and the collection efficiency of carriers is reduced.A scheme of modifying PEDOT:PSS film with discrete SnO₂ nanoparticles is proposed.A discrete SnO₂ nanoparticles layer is constructed on the surface of PEDOT:PSS film.This layer of discrete SnO₂ nanoparticles can not only ensure the effective extraction of holes to PEDOT:PSS film,but also reduce the diffusion of electrons from perovskite thin film to one side of PEDOT:PSS film,the recombination of carriers at the contact interface between perovskite film and PEDOT:PSS film is reduced.The carrier collection efficiency is improved.At the same time,the crystallization of perovskite films is improved.Finally,the photoelectric conversion efficiency of device is improved from 12.24%to 18.04%.（2）Using lead acetate as the lead source of perovskite film,a high-performance p-i-n perovskite solar cell with PTAA as hole transport layer was successfully prepared without cross solvent treatment.In this part of work,in view of the poor repeatability of device preparation caused by the large use of anti-solvent in the conventional preparation of perovskite films,we successfully prepared high-quality perovskite films without anti-solvent by using Pb（Ac）₂ instead of Pb I₂ as perovskite lead source,SEM,XRD,steady state fluorescence and transient fluorescence attenuation show that the perovskite films prepared with lead acetate as lead source have higher quality,and the photoelectric conversion efficiency of the champion photovoltaic devices reached 19.37%,and the open circuit voltage of the devices reaches 1.129 V.In addition,the residual charge test technology is used to test the p-i-n perovskite solar cells prepared based on Pb（Ac）₂ and Pb I₂ as lead sources respectively.It is found that the carriers are easy to be captured by carrier traps parallel to the device interface,which affects the performance of perovskite solar cells.It provides some new ideas for the characterization of photovoltaic characteristics and the analysis of working mechanism of solar cells.（3）Preparing high performance p-i-n type FA-perovskite solar cells without anti-solvent by NMP as additive.In this part of work,we aimed at the problem of narrow absorption spectrum and low short-circuit current density of MA-perovskite solar cells,we use FA as the main cation of perovskite,and add high boiling solvent NMP into the perovskite precursor solution to effectively improve the crystallization quality of perovskite films.We prepared high quality FA-perovskite film by using the repair effect of water in air annealing perovskite films.Benefit to the broadening of absorption spectrum and the significant extension of carrier life,the photoelectric conversion efficiency of p-i-n type FA-perovskite solar cells prepared by anti-solvent free process to 20.9%.