Design Of Charge Transport Materials And Interface Modification For Perovskite Solar Cells

In recent years,solution-processed perovskite solar cells（PSCs）have encountered enormous progress due to excellent peoperities of perovskite materials.For the design of device architecture,charge transport materials and their interfacial modifications are essential to acquire efficient and stable PSCs.In this dissertation,various n-type and p-type semiconductors are employed in n-i-p type perovskite solar cells（PSCs）to investigate the influence of charge transport materials and interfacial modification on efficiency,stability and interfacial charge transport property in both single-junction PSCs and perovskite/organic tandem devices.（1）Low-temperature processed TiO₂ contains numberous defect to raise instability.In this work,n-type conjugated small molecules were inserted between TiO₂ electron transport layer and MAPb I₃ perovskite,to inverstigate the effect of interfacial layer on light-soaking instability.Research show that the photogenerated electrons will accumulate at the interface of TiO₂/MAPb I₃ without the presence of the interface layer,causing severe light-soaking.When interfacial layers are added,the interfacial defects are partially or fully passivated by PDI2 or PC₆₁BM,which leads to the suppression of interfacial charge accumulation,thus alleviating or eliminating light-soaking issue.（2）Metal oxides TiO₂,SnO₂ and ZnO electron transport materials were employed in CsPbI₂Br PSCs to investigate their influence on the efficiency and stability.Research show that the organic ligand Ac^-of ZnO film and the Cs⁺of CsPbI₂Br perovskite can form a stable Cs-Ac interaction to passivate defects and stabilize perovskite lattice structure,leading to the best efficiency and stability,which are much better than those of TiO₂-and SnO₂-based counterparts.（3）To solve the poor reproducibility and stability of Spiro-OMe TAD based PSCs,dopant-free p-type polymer PBDB-T and its derivatives were employed as the hole transport materials in ZnO-based CsPbI₂Br PSCs.Device studies show that the alkylsilyl substituted PBDB-T-Si based device obtained the highest PCE of 15.60%with minimized hysteresis.Investigation supports that the quasi-Ohmic contact of PBDB-T-Si with pervoskite reduces the hole transport barrier in PSCs,thus the high hole mobility of polymer can achieve more balanced electron and hole transports to benefit performance.（4）Targeting at the crucial significance of the interconnecting layer in determing performance of tandem solar cells,CsPbI₂Br/PM6:Y6-BO tandem solar cells were fabricated to investigate the influence of polymers in interconnecting layers on performance.Investigations show that,poly TPD has merits of low parasitic absorption,favorable hole mobility and quasi-Ohmic contact in the interconnecting layer,therefore maximizing photon absorption of the active layers and minimizing charge accumulation and voltage loss of the tandem device,leading to the highest performance with 21.1%,and tandem device was received with superior storage,UV irradiation and thermal stability.In this dissertation,device performance,light-soaking,hysteresis and long-term stability were investigated by employing organic conjugated small molecules,organic conjugated polymers and metal oxides as charge transport materials and interfacial materials,which could passivate interfacial defects and improve interfacial charge transport,and fabricate high efficient and stable single-junction perovskite and perovskite/organic tandem solar cells.