Research On Processing Optimization And Influencing Factors In Carbon Electrode Perovskite Solar Cells

The perovskite solar cells?PSCs?were firstly invented in 2009,then their power conversion efficiencies?PCEs?have reached the efficiencies of silicon solar cells just after 9 years development.The PSCs are expected to continually break through and become a new generation of solar cells.At present,the reported high efficiency PSCs are mainly based on structure with hole transport layer?HTL?,where the HTL materials used in such structure are expensive and unstable material.Meanwhile,noble metals,for example,gold?Au?and silver?Ag?are necessarily used as electrode materials,which are not suitable for the low cost and large-scale production of solar cells.Contrastly,carbon electrode PSCs without HTL are cheap in preparation cost,simple in preparation technology and easy in industrial production.But so far,the efficiencies of carbon electrode PSCs are relatively lower than those of HTL PSCs,so the key point is to improve PCEs of carbon electrode cells.In this dissertation,the experimental optimization process of carbon electrode PSCs is studied from experimental research and theoretical simulation,and the key factors which influence cell performances are further revealed.The contents of the dissertation are as follows:1.The preliminary preparation scheme of carbon electrode PSCs are systematically optimized.The temperature 70?is introduced as the optimal temperature for the lead iodide?PbI₂?precursor solution,then the annealing temperature for perovskite films is adjusted from 70?to 100?.The concentration of PbI₂ precursor solution and methyl ammonium iodide?CH₃NH₃I,simplified as MAI?solution are optimized from 1.0 M?mole per liter?and 30 mg/ml to 1.2 M and 15 mg/ml,respectively,then PCE is enhanced from the initial 3.59%to 7.19%.Thus the initial experimental scheme is obtained.2.Combining with the continuity equations which describe the non-equilibrium carrier motion in semiconductor,the influences of defects on carrier distribution under different illumination conditions were simulated.The influence range of defects is qualitatively investigated,and the“growth nature”of the defects is revealed.It is considered that a high quality perovskite layer is the basis of the outstanding properties of perovskite materials.According to the simulation results,we put forward two experimental processes to further optimize cell performances:the PbI₂ precursor solution filtrating technology and the auxiliary solvent DMSO process,then the corresponding cell efficiencies increase from 7.19%to 7.64%and 8.66%,respectively.A further optimized experimental scheme is obtained by combining these two processes and detailed experimental control,and the highest cell efficiency is up to 10.02%.3.The effect of four different factors such as PbI₂ residual,the surface morphology of perovskite film,the surface roughness of perovskite film,and the contact status of the perovskite/carbon electrode interface on cell performances are systematically investigated.It is found that for carbon electrode PSCs,the contact status of the perovskite/carbon electrode interface is the primary factor which limits cell performances,and reducing the surface roughness of perovskite film can effectively improve the contact status.In the case of poor contact,even if other factors are well controlled,it is still difficult for cells to exhibit high efficiency.