Ion Passivation And Photoelectric Properties Of TiO₂ Electronic Transport Layer And Research Of Lead-free Selenium Cell

Organic-inorganic hybrid perovskite material CH₃NH₃PbX₃?X=Cl,Br,I?due to its low exciton binding energy,long carrier diffusion length,suitable forbidden band width,high light absorption coefficient and solution processing performance has received increasing attention in recent years.The efficiency of photovoltaic devices based on this hybrid perovskite material has broken through 22.700%and can basically reach the level of crystalline silicon solar cells and it is regarded as a candidate for next-generation photovoltaic devices.In this study,we made alteration between perovskite layer and the electron transport layer to improve the photoelectric conversion efficiency of the perovskite solar cell.Titanium dioxide?TiO₂?is used as the electron transport layer,and the Hexadecyl trimethyl ammonium Bromide?CTAB?/isopropanol solution is spin-coated onto the surface of TiO₂,with the doping of halogen anions,the conductivity is enhanced and electron transport between the perovskite layer and the electron transport layer is boosted as well.Furthermore,the perovskite material CH₃NH₃PbX₃ contains the heavy metal element Lead,it can accumulate in the living body,poisoning humans and potentially harming the environment,which makes the prospect of large-scale commercialization of PSCs dim.Therefore,it is inevitable to study PSCs with less Lead and Lead-free.In this paper,Selenium was used to replace the perovskite material CH₃NH₃PbX₃ to prepare non-Lead solar cells.First,the CTAB/isopropanol solution is spin-coated on the surface of the dense TiO₂ electron transport layer.We can increase the electrical conductivity via regulation of the concentration of CTAB and introducing Br between the electron transport layer and the perovskite layer.In other words,we boost the speed of electrons extracted from the perovskite layer and transmitted to the TiO₂ electron transport layer and improve the photoelectric conversion efficiency of cells simultaneously.Scanning electron microscopy shows that the perovskite film prepared by spin coating on the TiO₂ surface after CTAB treatment was denser and more uniform,it's roughness of surface and voids were reduced.The maximum photoelectric conversion efficiency of perovskite solar cells after interlayer treatment can reach 15.072%,which is higher by 0.249 than cells without modification.Then,a non-Lead system solar cell was prepared by using selenium as a light absorbing layer.As an essentially non-toxicmaterial,selenium related equipment is generally environmentally friendly and acceptable to the public.In addition,selenium is stable and has a suitable 1.8 eV direct bandgap with absorption coefficient of 10⁴ cm^-1,which can be used as an excellent light absorbing layer material.In this experiment,selenium powder??99.99%,?200 mesh?was used as a source of selenium,hydrazine hydrate as a solvent,using a simple and facial solution spin coating process to prepare selenium film.The cell prepared in air and finally we obtained 1.2300%of the photoelectric conversion efficiency.