Optimizing The Transport Layer To Improve The Performance Of Perovskite Solar Cells

Organic-inorganic hybrid perovskite is the main material for making perovskite solar cell(PSC).The material generally has the properties of high carrier mobility,longer carrier diffusion length and less exciton binding energy.This makes the development prospects of PSC broad and rapid.In a short period of time,its photoelectric conversion efficiency(PCE)has reached a commercial level.What is interesting is that PSC,as a thin-film solar cell,also has problems such as interface contact and a large number of recombination of carriers at the interface.Therefore,modifying interface can passivate the contact defects of the device and reduce the contact loss at the interface.As one of the key functional layers in the PSC system,the properties of the Hole Transport Layer(HTL)itself and its impact on the overall device are very important.Especially when the PSC is inverted,the HTL collects and transports holes,and the light-absorbing layer is also grown on the HTL.Therefore,HTL has an important impact on the performance of PSC devices.Based on the MAPb I₃lead-based PSC,this paper mainly focuses on the influence of adjusting the interface between the hole transport layer and the perovskite layer on the perovskite film formation quality and device performance.The specific work is as follows:(1)Using organic small molecule 4,4'-cyclohexylidenebis[N,N-bis(p-tolyl)aniline](TAPC)as the intermediate layer to modify NiO_xHTL and fabricate high-efficiency perovskite solar cell devices,the V_OCand J_SCof PSC have been significantly improved.The results prove that the proper TAPC modification of NiO_xcan reduce charge recombination and transport loss.The performance of PSC using TAPC as the modification layer of the hole transport layer is significantly improved,which is due to the enhancement of V_OCand J_SC.This is due to the increase in the selective effect of the NiO_x/PVSK interface on carriers,the reduction of the potential barrier,and the enhancement of hole selectivity.And it can block the electron transmission,so that the dark current density is reduced.Finally,the PCE of PSC devices increased from 16.37%of unmodified devices to 18.86%.(2)The introduction of a modified layer will inevitably increase interface contact,so we explored a more convenient way to optimize the hole transport layer——doping the p-type small molecule doped material 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane(F4TCNQ)into the hole material NPB.Through experiments and tests,it is found that doping with the small molecule material F4TCNQ can reduce the roughness of the HTL film,optimize the interface contact,and improve the carrier diffusion ability.Finally,the PCE increased from the initial 13.7%to the optimized 15.7%.However,the FF of PSC devices has not been effectively improved.(3)In order to further optimize the morphology of the film and improve the FF of the device,wechooseahighlyhydrophobicorganicpolymerPoly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine](Poly-TPD)as the research object to explore the optimization effect of incorporating Poly-TPD into the hole transport material N,N'-Di-[(1-naphthalenyl)-N,N'-diphenyl]-1,1'-biphenyl)-4,4'-diamine(NPB)for the overall optimization of HTL and PSC devices.The research results show that the incorporation of highly hydrophobic Poly-TPD can improve the surface roughness of the NPB transport layer,passivate the contact defects between the HTL and the perovskite layer,and improve the quality of the perovskite film,improve the photoelectric performance and stability of the device.Finally,we realized the optimization of the device performance,and the PCE increased from 13.77%of the original device to 16.78%after the optimization.