Performance Optimization Of P-i-n Type Perovskite Solar Cells By Antisolvent Method

Compared with perovskite solar cells with a regular structure(n-i-p type),the newly emerged one with an inverted structure(p-i-n type)has attracted the attention of many scientists because of such advantages as simple stacking and low-temperature processing.The quality of the perovskite film which is the core part of the device is of great importance.Therefore,it is necessary to develop new film deposition methods to obtain high-quality perovskite materials.The antisolvent-assisted one-step spin coating method(referred to as the antisolvent method)is one of the effective methods for preparing perovskite films in laboratory,and contains only several simple steps to prepare perovskite films with high quality.Therefore,the systematic optimization of the antisolvent method is of great significance to obtain perovskite solar cells with good performance.At present,few studies have focused on specific antisolvents,combining the solvent ratio of precursor and the processing method of antisolvent for systematic exploration.Therefore,based on the MAPb I_xCl_1-x perovskite,?-butyrolactone(GBL)and dimethyl sulfoxide(DMSO)were used as solvents and chlorobenzene(CB)was used as antisolvent.The optimal solvent ratio and the optimal processing method of CB were explored to prepare the devices with the best performance.Then,C₆₀ and C₇₀were respectively introduced into perovskite films through CB.The influence of this processing method on the quality of perovskite films and on the performance of the devices was explored.The main research contents are as follows:(1)In the system in which the ratio of PbI₂,PbCl₂and MAI is 1.25 M:0.15 M:1.3 M,the solvents are GBL and DMSO and the antisolvent is CB,the optimal processing method was obtained,which is 7:3 for the solvent ratio,500?L for the volume of CB and the last10th second before the spin coating process is finished for the dripping time of CB.By this method,the devices with an average efficiency of 13.86%were obtained.By exploring the effects of the processing method of CB on the quality of perovskite films,it is found that with the increase of the amount of antisolvent,the grains of the perovskite films gradually reduce to the appearance of holes,and the content of Pb I₂which is not converted into perovskite in the interior of the perovskite films decreases first and then increases.Excessive Pb I₂ is accompanied by a decrease in the crystallinity and an increase in defect density of the films.With the advance of the dripping time of CB,pores gradually appeare on the surface of the films,the content of Pb I₂ increases,and the surface roughness becomes larger.They result in poor interface contact between the perovskite layer and the electron transport layer.(2)C₆₀ and C₇₀ were separately introduced into the devices with the structure of ITO|PEDOT:PSS|MAPb I_xCl_3-x|PC₆₁BM|Ca|Al through CB,and the efficiencies are increased from 11.89%to 13.81%and 13.40%respectively.The introduction of C₆₀ or C₇₀ makes the grains of perovskite films larger and closely connected,thereby increasing the J_scand FF of the devices.Then,C₆₀ and C₇₀ were separately introduced into the devices with the structure of ITO|PEDOT:PSS|MAPb Ix Cl_3-x|PC₆₁BM|PEI|Ag through CB,and the efficiencies are increased from 13.38%to 14.76%and 13.90%respectively.The introduction of C₆₀ or C₇₀reduces the surface roughness and increases the absorbance of perovskite films,thereby increasing the V_ocand J_sc of the devices.