Drop-coating Preparation Of Perovskite Layer And Optimization Of Interfacial Contact For Low Temperature Carbon Based PSC

Perovskite solar cell?PSC?has attracted wide attention for its high optical absorption coefficient,high photoelectric conversion efficiency?PCE?and low cost.The low temperature carbon based PSC is developed on the basis of traditional mesoporous PSC and fully printable HTM-free PSC,it not only inherits the excellent film performance of the former,but also possesses the latter's simple fabrication and large area.However,the current perovskite layers are mostly fabricated by spin-coating,which is difficult to achieve large area,and the interfacial contact between doctor-bladed carbon layer and perovskite layer is poor,which limits the improvement of cell performance.For solving above problems,this paper explores the preparation of perovskite layer by drop-coating method and optimizes the interfacial contact of carbon layer and perovskite layer?C/CH₃NH₃PbI₃?.The detailed contents are as follows:Firstly,the preparation process of perovskite layer by drop coating method was studied.It was revealed that the solvents,amounts and permeation ways of perovskite layer and the effect of ZrO₂ spacer layer on cells had important influence on cell performance.Above all,the film got the best performance when using DMF and DMSO as solvent of perovskite solution;Next,when the amount of was optimized to 5×0.6?L,the film had good light absorption and the best performance came into being;And the permeation way also enhanced the cell performance well through the physics method and chemistry method,resulting a better PCE.Otherwise,a ZrO₂spacer layer could suppress the dark current,weaken the carriers recombination and improve cell's PCE and its air stability,as well.Secondly,to enhance the interfacial contact of C/CH₃NH₃PbI₃,the ACN solvent,which can dissolve CH₃NH₃PbI₃,is added in the carbon slurry.Results show that using ACN as solvent of carbon slurry can enhance the interfacial contact of C/CH₃NH₃PbI₃ obviously,while DMF doesn't has this effect;And when the content of ACN is 5wt.%,the PCE of PSC comes to the highest because of its best interfacial contact enhancement;What's more,the effect of interfacial contact enhancement not only works for the drop coating perovskite layer,but also works for the spin coating perovskite layer.It is also revealed that after treated with ACN contained solvent,the size of many crystalline grains change.The co-existence of small and big sized grains are beneficial for the light scattering of perovskite layer,leading to a effectively improvement of the cell's current density and PCE.Thirdly,the composition of our double carbon layer also has influence on the interfacial contact of C/CH₃NH₃PbI₃.Results show when the ratio of graphite and carbon black in upper and lower carbon layer are set as 5:1 and 1:1 separately,the conductivity and interfacial contact of C/CH₃NH₃PbI₃can be both guaranteed;We also studied the thickness of lower carbon layer and the additive of CNT or rGO in upper carbon layer to optimize the conductivity of our double carbon layer.