Research On The Effects Of Interface Modification On The Performance Of Lead Halide Perovskite Solar Cells And Their Mechanism

The photoelectric conversion efficiency（PCE）of PSCs boosted from3.8%to 25.7%in just about a decade,which makes PSC one of the most promising candidates for the next generation solar cells.However,the poor long-term stability of PSCs hinders their further development and commercialization.The interfaces within PSCs have non-negligible effects on the performance and stability of the device.What’s more,interfacial non-radiative recombination is the main reason for the deterioration of device performance and stability.In this paper,for the propose of suppressing interfacial non-radiative recombination and improving the efficiency and stability of perovskite solar cells,we have done the following work on the SnO₂electron transport layer/CH₃NH₃Pb I₃ light absorbing layer interface and the CH₃NH₃Pb I₃ light absorbing layer/Spiro-OMe TAD hole transport layer interface in PSCs.（1）PVB was used to modify the SnO₂/CH₃NH₃Pb I₃ interface.The influence of the PVB bottom modification on morphology,structure,light absorption properties of CH₃NH₃Pb I₃ perovskite films and efficiency,stabbility and carrier dynamics of CH₃NH₃Pb I₃PSCs was systematically investigated,the influence mechanism was also analyzed.The PVB bottom modification significantly improves the quality of CH₃NH₃Pb I₃ perovskite films deposited on SnO₂ and reduces the leakage current problem due to poor film coverage.Meanwhile,the better energy level alignment is achieved at the SnO₂/CH₃NH₃Pb I₃ interface after PVB modification,facilitating the electron extraction at interface.The C=O in PVB can interacts with defects on the surface of CH₃NH₃Pb I₃ perovskite films,passivating interfacial defects,suppressing the non-radiative recombination,reducing energy loss.Thus the efficiency of the device is improved.In addition,the improved stability after PVB modification owes to the hydrophobicity of PVB which inhibits the moisture-induced perovskite degradation and the stabilization of perovskite structure by the hydrogen bonds between PVB and CH₃NH₃Pb I₃.（2）Acetophenone was used to modify the CH₃NH₃Pb I₃/Spiro-OMe TAD interface.The influence of the acetophenone top modification on morphology,structure,optical properties of CH₃NH₃Pb I₃ perovskite films and efficiency,stabbility and carrier dynamics of CH₃NH₃Pb I₃PSCs was systematically investigated,the influence mechanism was also analyzed.There is interaction between the C=O of acetophenon and the under-coordinated Pb²⁺on the surface CH₃NH₃Pb I₃ perovskite films,reducing interfacial defects,suppressing interfacial non-radiative recombination.Theπ-conjugated structure of benzene ring can facilitate the carrier transport within PSCs,simultaneously.Therefore the efficiency of PSCs is ameliorated.Moreover,the high cohesive energy of benzene ring enables acetophenone to easily assemble at grain boundaries.The hydrophobic benzene ring helps to prevent the moisture ingress along grain boundaries,inhibiting the moisture-induced perovskite degradation process,thereby improving the stability of the device.（3）The FTO/SnO₂/PVB/CH₃NH₃Pb I₃/Acetophenone/Spiro-OMe TAD/Au device was fabricated.PVB-bottom-acetophenone-top bilayer interface modification can concomitantly passivate interfacial defects at SnO₂/CH₃NH₃Pb I₃interface and CH₃NH₃Pb I₃/Spiro-OMe TAD interface,which further suppresses interfacial non-radiative recombination.PVB bottom modification enables better energy level alignment at SnO₂/CH₃NH₃Pb I₃interface and acetophenone top modification facilitates the carrier transport.These help to improve the efficiency of the device further.The efficiency of the bilayer-modified device improved by 42.64%compared with the unmodified one.Bilayer interface modification significantly ameliorates the device stability as well,which attributes to the inhibition of moisture-induced perovskite degradation progress by the two hydrophobic interface modifiers.The bilayer-modified device remained 76%of its initial efficiency value after stored in ambient air（relative humidity～55%,25℃）for 42 days,exhibiting significantly enhanced stability.While the efficiency of the unmodified one decreased to 0 just in27 days.This paper proposes bilayer interface modification methods for improving the efficiency and stability of lead halide perovskite solar cells,which also provides scientific basis and theoretical guidance for pushing the commercialization process of PSCs.