Research Of Enhancing Efficiency And Stability Of Inverted Perovskite Solar Cells Based On Electrode Contact Modification

In recent years,perovskite has attracted widespread attention for its excellent photoelectric properties,low cost and simple fabrication.The power conversion efficiency?PCE?has developed rapidly,which has achieved more than 25%for single heterojunction perovskite solar cells?PSCs?.However,the long-term stability put obstacle in their further industrialization.Besides,the unique merits of inverted PSCs have been illuminated compared with other structure PSCs for its low temperature solution fabrication,which is not only in conformity with the requirements for flexible devices and roll to roll printing process,but also easily integrated to the tandem PSCs.It has showed a great potential for commercial application.However,the PCE of inverted PSCs are still lower than that of conventional ones,mainly due to the open-circuit voltage(V_OC)loss caused by non-radiative recombination.As a result,the inverted PSCs both with high performance and stability have become research hot-point.In our work,interface issues are as the entry point and sovled based on the strategies of perovskite components,interface and doping engineering to reduce the voltage loss caused by non-radiative recombination and improve the performance and stability for inverted structure solar cells.The work is mainly divided into three sections as following:1.Two perovskite components with high stability are selected and employed for inverted PSCs fabrication,which are Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃?FAMACs?and FA_0.83Cs_0.17PbI_2.7B_r0.3?FACs?.The PSCs with two components are fabricated with inverted architecture of ITO/PTAA/Perovskite/C60/BCP/Cu.The impact of bulk passivation and interface on performance for inverted PSCs are investigated and the champion inverted PSCs based on FAMACs and FACs are achieved with PCE of19.4%and 19.1%by optimizing,respectively.In addition,the V_OCC loss caused by energy level mismatch is investigated preliminarily by gradient energy level construction.2.Interfacial engineering strategy is employed by introducing a hybrid ligands interfacial layer to modify cathode contact for inverted PSCs based on FAMACs and reduce the V_OCC loss caused by non-radiative recombination.As a result,the performance and stability of inverted PSCs are both enhanced simultaneously.Heavily washed QDs are used as a neutral charged intermedia to enable alloying reaction to transfer ligands without damage PVKs.A band bending immediately generates on perovskite top surface after QDs modification.As a result,50 mV increased V_OCC is achieved,leading to a V_OCC of 1.15 V and a PCE of 20.6%in inverted PSCs even without the passivision of hybrid ligands.Meanwhile,enhanced stability is achieved for these devices after QDs modification,in which PCE keeping 94%of initial value after 1000 hours'storage in N₂ atmosphere.3.Doping engineering strategy is employed by doping PFN-Br,a conjugated polymer in perovskite film to modify anode contact for inverted PSCs based on FACs and reduce the V_OCC loss caused by non-radiative recombination.As a result,the performance and stability of inverted PSCs are both enhanced simultaneously.The PSCs with PFN-Br doping could narrow the energy gap between perovskite and PTAA by shifting the VBM of FACs perovskite film from-5.8 eV to-5.6 eV.In addition,it is also beneficial for the quality of perovskite film with reduced defect density and increased the grain sizes to further overcome the barriers in the interface between PTAA and perovskite.Carrier extraction and transportation are highly encouraged at the surface of PTAA/perovskite.As a result,a 60 mV increased V_OCC is achieved,which promotes champion device efficiency to 20.3%.At the same time,the efficient device displays significantly enhanced stability under continuous illumination and bias at MPP condition,which could remain 80%of its initial PCE under continuous illumination of one sun for 536 h.