Alkali Metal Cations Doping And Interface Engineering In Perovskite Solar Cells

In recent years,perovskite solar cells have attracted more and more researchers’attention due to their simple preparation process,low cost,and high efficiency.The photoelectric performance and stability of perovskite solar cells are closely related to perovskite composition and charge transport layer.In this paper,perovskite solar cells with high efficiency and stability based on TiO2-nanorods structure,SnO2 planar structure and flexible substrate were prepared by alkali metal ion doping of perovskite and interface engineering of electron transport system.Compared to mesoporous structure,TiO2 nanorod arrays have higher electron mobility and less defect density,so they can be used to fabricate perovskite solar cells with higher efficiency.However,the hole blocking ability of the spin-coated nanorod seed layer(S-TiO2)is difficult to meet the requirements of highly efficient devices.In order to solve this problem,a A-TiO2 layer of 5nm was deposited between FTO and S-TiO2 by atomic layer deposition to reduce the energy level barrier and charge recombination.Subsequently,the thickness of S-TiO2 layer was further optimized.In the end,the champion efficiency of perovskite solar cells with optimized structure reached 20.28%.Previous studies have shown that the doping of alkali metal ions(Cs+,Rb+,K+,et al)is beneficial to the performance and stability of perovskite solar cells.In this paper,CsFAMA-based perovskite films doped with different Rb+/K+ratios were prepared.The effects of Rb+and K+doping on the crystallization and photoelectric properties of perovskite films were studied in detail.The results showed that the function of Rb+and K+doping in perovskite was quite different.By optimizing the ratio of Rb+/K+,the performance of perovskite solar cells was improved,while the hysteresis effect was reduced and the stability was enhanced.The SnO2 planar perovskite solar cells with optimum perovskite composition as light absorbing material could achieve a maximum efficiency of 20.52%and average efficiency of more than 20%.Flexible perovskite solar cells are suitable for roll-to-roll manufacturing,which can greatly reduce industrial cost and have broad application prospects.However,the photoelectric conversion efficiency of flexible perovskite solar cells is still lagging behind that of rigid devices.Herein,a super-thin HfO2 film was introduced between ITO electrode and SnO2 electron transport material by low-temperature atomic layer deposition,which significantly inhibits charge recombination at the interface.The champion efficiency of flexible perovskite solar cells modified by HfO2 could reach 19.11%.