Highly Performance And Stability Of Planar Heterojunction Perovskite Solar Cells

The organic-inorganic hybrid perovskite solar cells(PerSCs)have attracted wide attention due to their advantages of high power conversion efficiency,simple preparation process and low cost of raw materials.According to the charge flow direction,Planar heterojunction perovskite solar cells can be divided into n-i-p type and p-i-n type.Two interfaces are formed between perovskite film and hole/electron transport layer,where efficient charge separation can be realized.FTO which is modified by PEDOT: PSS can obtain high work function.However,the work function of PEDOT: PSS is 4.9-5.2 eV,and there is still 0.2-0.5 eV barrier compare with HOMO level of CH3NH3PbI3.In addition,PEDOT: PSS has acidic and hygroscopic nature,which will affect the long-term stability of the device.In this study,we focused on optimizing the properties of PEDOT: PSS hole-transporting layer by using additives or additional hole transport materials to increase the performance of PerSCs.The details of studies are as follows:1.A WOx hole-transport layer with high work function was inserted into the PEDOT: PSS and FTO to enhance the stability and photovoltaic performance.The inserted WOx layer not only can avoid direct contact between PEDOT: PSS and FTO,but also can further reduce the contact barrier between the electrode interface.We studied the effect of WOx /PEDOT: PSS double-layered hole transport layers on the optical transmittance,the morphology and crystals of perovskite,the photovoltaic performance and the stability of the devices.The power conversion efficiency(PCE)of PerSCs can be improved from 10.56%(with PEDOT: PSS layer)to 12.96% with WOx /PEDOT: PSS double-layered hole transport layers,and the stability of the device has also been greatly improved.2.Nafion,which is an amphiphilic perfluorosulfonic copolymer,was doped into PEDOT: PSS to enhance the conductivity and stability of the the hole transport layer.Nafion is composed of perfluorinated sulfonate ester,and it is an excellent cation exchanger which has excellent thermal stability and mechanical stability.FTO which is modified by PEDOT: PSS can obtain high work function.With the Nafion doped PEDOT: PSS hole transport layer,the root mean square(rms)roughness of the hole transport layer has increased,which increased the contact area of the active layer.It is favorable for the transportation of carrier so that device performance has been improved.With the Nafion doped PEDOT-PSS hole transport layer,the power conversion efficiency of the PerSCs reaches 15.11%,increased by 26.9% in comparison with that of the control devices(11.91%).