Study On Phase Separation Of Mixed-Halide Perovskites

Organic-inorganic hybrid perovskite such as MAPb(BrxI1-x)3(MA=CH3NH3+)is a new type of direct bandgap optoelectronic semiconductor materials,which has made great achievements in photoelectric conversion.As a new generation of optoelectronic materials,it has a broad absorption spectrum,high absorption coefficient,high carrier mobility and the band gap can be changed by adjusting the ratio of mixed halide.For example,MAPb(BrxI1-x)3 system is an ideal candidate for tandem solar cell.Perovskite-based light-emitting diodes have the characteristics of high brightness,pure color,high stability,high transparency,adjustable emission wavelength,and good compatibility with transparent substrates.Therefore,perovskite materials are also expected to guide the next display technology revolution.Unfortunately,under the stress of light or electric field,the instability of MAPb(BrxI1-x)3 system is exposed,and it is easy to form iodine-rich and bromine-rich domains,resulting in a relatively low open circuit voltage of perovskite-based solar cells.The emission peak becomes pinned at low emission energies characteristic of the I-rich domains,precluding spectral tunability.This article will detail the origin of phase separation of mixed halogen perovskites and methods that can effectively inhibit phase separation.And on this basis,two methods are proposed to effectively suppress phase separation:1.Introduction of long chain of organic amines(n-Butylamine,BA)By utilizing the self-assembly effect of long-chain n-butylamine,the perovskite grains can be effectively isolated to form nano-sized quasi-two-dimensional perovskites,thereby effectively inhibiting the phase separation of the mixed halogen perovskite system.Based on this foundation,we have prepared a stable and efficient perovskite light-emitting diode with adjustable emission wavelength.2.Passivation of vacancies of halide ions with oxygen ionsUnder light conditions,oxygen accelerates into the perovskite film.Theoretical calculations show that oxygen ions have a very high probability of occupying halide vacancies,thereby reducing the channel of halide ion movement to inhibit phase separation.