Effects Of Organic Halide Salts On The Surface Of Perovskite Films And The Performance Of Solar Cells

Organic-inorganic hybrid perovskite solar cells have attracted extensive attention from the scientific community due to their advantages such as simple manufacturing process,low manufacturing cost,appropriate energy gap,high light absorption coefficient,low electron-hole exciton binding energy,carrier balance and long photoinduced carrier life.In recent years,researchers have promoted the efficiency of perovskite solar cells from 3.8%to 25.2%through the use of perovskite film crystal growth control,interface engineering,selection of appropriate carrier transport layers and surface passivation.The current ratio of open circuit voltage(V_oc)to band gap?E_g?of perovskite solar cells is between 0.67 and 0.70.Compared with the 0.80value of amorphous silicon and gallium arsenide thin-film solar cells,there is still a large gap.Therefore,the possibility of further increasing the efficiency of perovskite solar cells by increasing V_oc is still attractive.In this study,the performance of perovskite solar cells was improved mainly by regulating crystal growth and interface passivation.On the one hand,the grain boundary of the perovskite polycrystalline film is considered to be a defect region,which not only provides carrier recombination sites,but also introduces a device degradation pathway.Efforts to expand the grain size of perovskite thin films and reduce their grain boundary defects are essential for the preparation of highly efficient and stable perovskite solar cells.Therefore,the charge loss caused by the grain boundary recombination of photogenerated charges can be reduced.For flat heterojunction perovskite batteries prepared using a low temperature solution method,this increased efficiency may be beneficial.On the other hand,in solution-treated polycrystalline perovskite,defects mainly exist in the front and back sides and the boundary between the crystal grains.Therefore,the further development of perovskite solar cells may depend on how to reduce the defect density(N_defect)in perovskite semiconductors.In order to reduce the surface defects of perovskite films,surface passivation treatment is necessary.Studies have shown that post-treatment of perovskite films with organic halide salts?such as phenethyl ammonium iodide?can also reduce defects,inhibit non-radiative recombination,and improve device efficiency.This study is mainly divided into two parts.In the first part,we tried to adulterate organic halide salts with amino groups into three-dimensional perovskite.Experiments have shown that the introduction of organic halide salts can improve the open circuit voltage of the device.Beneficial,but the hysteresis of the device is obvious.Another part of the work is to use butyl ammonium iodide?BAI?to passivate the defects of perovskite films.The amino functional group in the BA molecule can fill the negatively charged defect existing on the surface of the perovskite,thereby neutralizing the defect.We also observed an increase in the grain size of the perovskite after BAI treatment.Passivated perovskite films exhibit enhanced photoluminescence?PL?and longer carrier lifetime.These phenomena indicate that the BAI treatment layer can reduce the loss of carriers due to charge recombination.Therefore,the certified power conversion efficiency?PCE?of the device reaches 21.1%.This article includes 42 pictures,4 tables,and 68 references...