| China’s dual-carbon strategy puts forward the goal of implementing green and low-carbon development,and will promote the development of related industries.In this case,the demand for renewable energy will continue to increase.Among them,photovoltaic power generation plays an important role in the long-term energy strategy because of its safe,clean,extensive and sufficient resources.Perovskite solar cells(PSCs),as a new type of solar cell material,have been developed for decades,and the photoelectric conversion efficiency has exceeded 25%.So far,the band gap of organic-inorganic hybrid perovskite solar cells prepared by one-step method is generally 1.6 e V or higher.However,perovskite with band gap in this range will seriously restrict the improvement of photoelectric performance of battery devices.At the same time,a large number of defects at the interface of the perovskite film will seriously affect the further improvement of the photoelectric performance of the device.Therefore,it is of great significance to develop efficient perovskite battery with narrow band gap and effective interface passivation scheme.On the other hand,unlike the rapid development of photoelectric conversion efficiency of devices,the understanding of the photophysical mechanism of perovskite semiconductor materials is not very deep.The previous research is usually limited by the resolution of conventional technical means and the mutual entanglement and penetration of the photophysical processes between different functional layers in the perovskite device,which makes the research on the micro-photogenerated exciton dynamics,such as the diffusion of photogenerated carriers in the film and the transfer of the interface,which are closely related to the photoelectric performance of the device,not yet thorough.Especially,the ultra-fast charge transfer at the perovskite/electron transport layer interface is very important for effectively extracting charge,and is also a key parameter for high-performance solar cells.This paper will focus on the application of machine learning(ML)in the development of narrow band gap perovskite,and explore the effect of halogen elements Br~-and Cl~-doping on the phase stability of perovskite crystals through ML simulation.Then,by using ultrafast spectroscopy technology,the dynamics of the diffusion of photogenerated carriers in perovskite bulk,the transfer and the recombination of perovskite/electron transport layer interface after the halogen element Cl~-doped with perovskite were systematically investigated.Finally,a large area,narrow band gap and high stability perovskite solar cell was prepared by optimizing the energy level of the electron transport layer.The specific research contents are as follows:(1)Through machine learning(ML)to help develop FA/MA organic hybrid efficient narrow bandgap perovskite solar cells.Through the simulation results,the best FA/MA ratio is obtained and verified by experiments.In order to improve the performance of narrow band gap perovskite thin films,machine learning is used to help explore the nucleation process of Cl element on perovskite thin films.The perovskite thin film with uniform size,compact interface and fewer defects was obtained through experimental verification,thus improving the photoelectric performance and environmental stability of the whole device.(2)Using transient spectroscopy technology,from the micro-exciton dynamics level and the multi-time domain scale of femtosecond to nanosecond,a diffusion-coupled interface charge transport model is constructed,and the charge process from perovskite to the electron transport layer is resolved into four fine photophysical processes,namely,thermal exciton cooling(HC)of～300 fs,electron bulk phase diffusion(BCD)of 300-800 ps perovskite 2-25 ps interface electron transfer(ICT)and 7-35 ns electron reverse recombination(BCR)process.The relationship between the concentration of MACl doping and the four photophysical processes mentioned above in the battery was discussed quantitatively.It was found that the phase diffusion of electron body and the electron transfer rate at the interface increased with the increase of the concentration of MACl doping,and reached the maximum value when the concentration of MACl doping was 0.4 m M;At the same time,the change of the electron reverse recombination rate with the doping concentration is contrary to the above trend,which is the essential reason for the optimal photoelectric performance of the battery doped with 0.4 m M MACl.(3)The interfacial transfer and intra-film diffusion of photogenerated carriers are the main factors that restrict the efficiency of solar cells.In order to improve the transmission performance of photogenerated charge at the interface,a dual-electron transport layer with energy band gradient was prepared.Finally,based on the double electron transport layer 5cm X 5cm.The photoelectric conversion efficiency of 5cm X 5cm large-area perovskite solar cell exceeded 18%. |
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