Background:With the continuous development of advanced solution processing technology and device structure of metal halide perovskite semiconductors, perovskite solar cells have risen rapidly in the energy field, which has attracted great attention from scientists. Metal halide perovskite semiconductors are a class of materials with excellent optoelectronic properties that can be used to make high-efficiency and inexpensive solar cells, providing new possibilities for the development of the renewable energy sector. The emergence of this field has led to in-depth research on perovskite solar cells in the scientific community. Among them, the focus is mainly on improving the performance, stability and optimization of the preparation process of the battery. The n-i-p device that deposited perovskites on the electron transport layer achieved an impressive 25The certified power conversion efficiency (PCE) of 7% offers hope for overcoming the Shockley-Queisser (S-Q) limit of a single junction. However, the efficiency of p-i-n perovskite solar cells prepared in air still lags behind that of cells prepared in an inert atmosphere, which has become an important challenge for current research. Brief introduction of the resultsIn light of this,Professor Xu Jixian of the University of Science and Technology of China and othersPublished the research results of "Inhibition of Halide Oxidation and Deprotonation of Organic Cations with Dimethylammonium Formate for Air-Processed P i N Perovskite Solar Cells" in Nature Energy. They focused on improving the preparation process, enhancing the crystallinity of perovskite films, and inhibiting defect formation on the surface and in vivo. In this context, the introduction of an ion-pair stabilizer, dimethylammonium formate (DMAFO), became a key part of the solution. The introduction of DMAFO inhibits the oxidation of iodide ions and the deprotonation of organic cations, thereby improving the crystallinity of perovskite films and effectively reducing defects in the films. The highlight of this study is that the entire preparation process was comprehensively considered, and the efficient and stable p-i-n perovskite solar cells were successfully fabricated in ambient air. In addition to surface passivation, the researchers have improved the bulk properties of the perovskite film and solved the additional p-type defects that arise when preparing cells under environmental conditions. By adding 1 molar of DMAFO as a stabilizer, 153-ev and 1The efficient and stable fabrication of perovskite solar cells with 65-EV bandgap shows its wide applicability. Under environmental conditions, especially at 25 30 and 35 50% relative humidity, the researchers successfully obtained 153 of the 24-ev batteryA stable efficiency of 72%, which is comparable to that of cells prepared in an inert atmosphere. 
**Reading guideIn order to stably prepare p-i-n solar cells in ambient air, the authors propose a"The whole process"The reduction of the stabilizer, ammonium dimethylformate (DMAFO), inhibits the deprotonation of organic cations and the oxidation of iodide ions, so that the perovskite precursor solution can be stored for a long time and shows good stability at ambient temperature. The effect of DMAFO on the solution was demonstrated by the NMR spectra (Figure 1B), where the signals of free DMA+ and HCOO- were observed, as well as the shift of the 1H-imine signal in the DMAFO+PBI2 solution. Using UV-VIS absorption spectroscopy (Fig. 1C,D), it was observed that the FAI solution containing DMAFOs remained transparent and colorless after accelerated aging in air, while the additive-free solution underwent oxidative discoloration, indicating that DMAFOs effectively inhibited the oxidation of halogens in air. This protective effect can be extended to the perovskite crystallization process in the air, improve the crystallinity of perovskite films, reduce the generation of local twins and the disorder of surface potential between grains, and inhibit defect-induced non-radiative recombination. 
Figure 1Stabilization of DMAFOs on perovskite precursor solutions in ambient airIn order to improve the effect of DMAFOs on the crystallization kinetics of perovskites prepared in ambient air, in-situ grazing incidence wide-angle X-ray scattering (GIWAXS) measurements were performed in this study. In the process of thermal annealing of wet films, the interaction between DMAFO and perovskites was studied by spinning perovskite solution and adding countersolvent (ether) dropwise to form a wet film. During the 2 h to 3C transition, the DMAFO samples exhibited strong scattering signals from the 4 h and 6 h second phases, which were not detected by the control group. This indicates that DMAFOs promote the formation of the secondary 4H 6H phase during crystallization, which is also verified in the 2D GiWaxs pattern in the middle, and is strongly correlated with the signal of the 3C phase after thermal annealing for more than 100s, indicating that DMAFOs contribute to the improvement of crystallinity. Eventually, the Giwaxs profile of the film showed more (100) and (200) peaks, confirming the higher crystallinity of the DMAFO sample. The azimuth integration of the (100) crystal plane shows that the diffraction signal of DMAFO is more directional and concentrated around the azimuth angle of 90°, indicating that DMAFO promotes out-of-plane growth. By changing the concentration of DMAFOs to analyze their position in the film, XRD tests found that when the content of DMAFOs increased from 0 to 4 mol%, the position of the diffraction peaks remained constant, indicating that the crystal structure of the perovskite bulk had not changed. Therefore, this study focused on the use of 1% DMAFOs for follow-up 153-EV perovskite thin films and devices. These results provide key experimental data for a better understanding of the effects of DMAFO on perovskite crystallization. 
Figure 2Effect of DMAFO on perovskite crystallization in ambient airFigure 3 reveals the effect of ambient air containing 1% DMAFO stabilizer on the surface and bulk phase of perovskite films by comprehensively analyzing the defects of perovskite samples prepared under different environmental conditions. First, the total Pb signal is obtained by integrating the Pb0 and Pb2+ peaks. The results showed that the PB0 PB ratio increased to 9% in the air-prepared sample, while in the air+DMAFO sample, the ratio was only 6%, which was comparable to the N2 sample, verifying the protective effect of DMAF in the ambient air manufacturing process. In addition, the relative atomic ratios of Ipb and Npb normalized to the N2 sample further showed that these ratios decreased in the air-prepared perovskite sample, but were restored in the air+DMAFO sample, indicating that DMAFO stabilizers can effectively reduce surface and bulk phase defects. Second, photoluminescence quantum yield (PLQY) and time-resolved photoluminescence (TRPL) measurements reveal the use of DMAFO stabilizers to reduce defect-mediated non-radiative recombination. The PLQY of perovskites prepared in air is reduced to 37%, while after treatment with DMAFO stabilizer, PLQY recovered to about 9%. The TRPL results showed that the attenuation rate of the Air sample was faster than that of the N2 sample, and the DMAFO stabilizer caused the perovskite prepared by ambient air to exhibit a slow TRPL trajectory similar to that of the N2 sample, indicating that DMAFO could effectively improve the non-radiative recombination process of perovskites. 
Figure 3Surface and bulk phase improvement of perovskite films prepared in ambient airFigure 4 uses the P-I-N solar cell structure and extracts the trap depth from the Arrhenius plot using the linear fitting of the DLTS peaks. It is found that the solar cells prepared in ambient air have a larger capture cross-sectional area than N2 solar cells, which leads to an increase in trap activity. In line with this, solar cells prepared in ambient air exhibit lower VOC and FF. However, solar cells prepared in ambient air with DMAFO stabilizers almost completely recovered these defects, and PCE reached a level similar to that of N2 solar cells. Further studies found that solar cells prepared in ambient air without DMAFO stabilizers reduced bulk recombination losses and exhibited similar performance levels to N2 solar cells compared to solar cells prepared in ambient air without DMAFO stabilizers. In addition, for 1The stability of DMAFO stabilizer in the preparation of 65-EV perovskite is also significantly enhanced, indicating that DMAFO stabilizer plays an important role in improving the performance and stability of perovskite solar cells prepared in ambient air. In summary, this study reveals the key role of DMAFO stabilizers in solar cells prepared in ambient air through multiple experimental results, which provides an important reference for the realization of efficient and stable perovskite solar cells. 
Figure 4Enhanced p-i-n perovskite solar cells prepared in ambient airSummarize the outlookThe highlight of this paper is the introduction of a whole-process stabilizer, dimethylammonium formate (DMAFO), into the preparation of perovskite solar cells. Through detailed experimental studies, the authors revealed the significant improvement effect of DMAFO in the preparation of p-i-n perovskite solar cells in ambient air. Firstly, DMAFO achieves long-term stable storage of perovskite precursor solution in ambient air by inhibiting the deprotonation of organic cations and the oxidation of iodide ions, overcoming the degradation problem in the preparation process. Secondly, DMAFO promotes the crystallization of perovskite films during the thermal annealing process of wet films, and improves the crystal quality. In addition, the inhibition of surface and bulk defects by DMAFOs and the significant improvement of cell performance have enabled perovskite solar cells prepared in ambient air to achieve performance levels comparable to those in inert atmospheres. Finally, the introduction of DMAFO stabilizer makes the solar cells prepared in ambient air not only have superior performance, but also exhibit excellent stability in long-term operation, which provides a new idea and method for realizing efficient and stable perovskite solar cells. Bibliographic informationmeng, h., mao, k., cai, f. et al. inhibition of halide oxidation and deprotonation of organic cations with dimethylammonium formate for air-processed p–i–n perovskite solar cells. nat. energy (2024).