Interface Regulation And Device Performance Of Inverted Perovskite Solar Cells

As the world is facing the problem of energy crisis,the development and utilization of clean and renewable new energy,especially solar energy,is of great significance for optimizing the energy consumption structure and reducing environmental pollution.Perovskite is highly favored by the community because of its high light absorption coefficient,large carrier mobility,tunable band gap,and easy fabrication.The power conversion efficiency of normal perovskite solar cell（PSCs）has exceeded 25%within 10 years,which is comparable to silicon-based solar cells.But the cost and stability issues still hinder its further commercial application.Moreover,inverted PSCs are becoming more and more popular due to their lower manufacturing cost,simpler and stable device structure and smaller hysteresis characteristics.The power conversion efficiency has exceeded 22%which still lags behind in efficiency and stability.We conclude that the defects at electrode interface and in perovskite active layer should mainly account for the low performance.The deficiency of electrode interface includes poor conductivity,large roughness,energy level mismatch and contacting reaction.In addition,there are also defects on the surface and interior of the perovskite,which affect the extraction and transmission of carriers.Therefore,it is of great significance to optimize the surface/interface property at electrode and active layer in PSCs.In this paper,we studied the modification of electrode based on Mo Ox modified anode and Zn O modified cathode and also the modification of perovskite layer by Ni I₂ doping,to improve device performance and stability,and promote the development of interface materials and devices.The main contents are as following:1.We processed P3CT-CH₃NH₂ as hole transport layer by low-temperature solution method,and prepared all-inorganic perovskite Cs Pb I₂Br with dopant Ni I₂ by one-step annealing process,which promote the crystallization and morphology of perovskite,increase the grain size and decrease the grain boundaries,passivate grain boundary defects and suppress carrier recombination.Compared with the reference PSCs,the stability of the devices have been significantly improved,and the power conversion efficiency（PCE）is also enhanced from11.97%to 13.88%.The optimal inverted device can maintain 81%of the initial efficiency after being kept in the air for 43 days,and could maintain 60%of the initial efficiency after 500 hours of continuous illumination.In this section,we provide a strategy for passivating the defects of perovskite,and improving device stability and PCE.2.We studied the interfacial regulation of solution-processed Mo Ox at anode in inverted organic-inorganic hybrid perovskite devices.The conductivity,roughness and energy level of Mo Ox are optimized by modifying the Mo Ox surface with strong charge-absorbing molecules F4-TCNQ,and the direct contact reaction with perovskite is avoided,which promote carrier transport at the interface and inhibit charge recombination.The champion PCE of 16.26%is achieved for the optimized device with negligible hysteresis,and it could retain over 95%of its initial efficiency after 150 h in ambient conditions（relative humidity 45%）and 95%after 40 h under continuous AM 1.5G illumination.Therefore,the interface modification strategy is of great significance to improve device stability and PCE.3.We studied the cathode with Zn O transport layer in inverted all-inorganic Cs Pb I₂Br PSCs.A small molecule TPPPS is adopted to modify Zn O cathode interlayer.The surface defects of Zn O and interface defects of Cs Pb I₂Br/Zn O are passivated,simultaneously.It provides a desirable energy level alignment between the Zn O and Cs Pb I₂Br.The PCE of the optimized device reach 14.62%with an extremely high V_OC of 1.25V.A huge improvement is demonstrared for the device stability,with only 20%loss after being placed in the ambient conditions for 18days,and maintaining 79%of the initial value after 32 days of illumination.This work provides an effective strategy for passivating metal-oxide type interface of cathode.