Study On Internal Packaging And The Stability Mechanism Of Efficient Perovskite Solar Cells With Carbon As Electrode

Perovskite solar cells(PSCs)have attracted widespread attention in the field of new energy due to their low cost,strong defect tolerance,and solution processability.However,the long-term stability issues of PSCs have hindered their commercial development.Developing encapsulation strategies is one of the ways to address the issues.Currently,there are two main encapsulation methods for PSCs: external encapsulation and internal encapsulation.External encapsulation can reduce water and oxygen infiltration,but commonly used materials,like EVA,lack sufficient permeability to both.Additionally,external encapsulation cannot solve the intrinsic stability and thermal degradation problems of perovskite films,leading to poor stability of PSC devices during long-term operation.To address these challenges,this article focuses on developing an internal encapsulation technique to improve the stability of perovskite films and PSC devices.The specific research work is outlined below:(1)The effects of different humidity and temperature conditions on the perovskite films and PSCs devices prepared in outdoor environments are investigated.Perovskite films and devices were prepared under two humidity conditions(25% RH and 80% RH).The results showed that perovskite films prepared under 25% RH conditions were smoother,denser,and had fewer impurities than those prepared under 80% RH conditions.PSCs devices prepared under 25% RH conditions had a 34% higher PCE than those prepared under 80% RH conditions.After aging under 85% RH conditions,the PCE of the device prepared under 25% RH conditions remained at 74% of its original value after 5 hours,while the device prepared under 80% RH conditions retained only 51% of its original value after 5 hours.Moreover,the devices prepared under 25% RH conditions showed improved thermal stability.After aging at 85°C for50 hours,the device retained 67% of its original PCE,while the device prepared under80% RH conditions retained only 51% of its original PCE.Although low humidity conditions can improve the long-term humidity and thermal stability of PSCs devices,the stability of unencapsulated devices remains poor.Therefore,internal encapsulation strategies are crucial for improving the stability of PSCs prepared in air.(2)This study suggests using a small molecule called FBA for internal encapsulation.This strategy protects the perovskite layer and improves the performance of PSCs.FBA treatment of the perovskite surface acts as an encapsulation layer that effectively passivates defects,suppressing non-radiative recombination,which in turn leads to an enhancement of carrier transport.Carbon-based PSC devices showed a PCE of 17.6% and lower hysteresis.Additionally,FBA significantly improves the hydrophobicity of the perovskite layer and PSCs devices.The FBA-encapsulated perovskite film did not exhibit any other non-perovskite phases,even after aging at 95%humidity for 5 hours,consistent with density functional theory calculations.Furthermore,PSCs devices maintained almost unchanged PCE under 50% humidity and 25℃ temperature for 100 days,demonstrating the effectiveness of FBA encapsulation in suppressing water damage and improving the humidity stability of the devices.(3)A new strategy for encapsulating PSCs with high molecular weight polyethyleneimine(PEI)has been proposed.By optimizing the concentration of PEI,the surface defects of the perovskite film were passivated and the charge carrier transport was improved.The champion device showed a 49% improvement in PCE compared to the original device,and hysteresis was significantly reduced.The stability of the device under high humidity was greatly improved,with the PCE remaining unchanged for 10 hours under conditions of 80% humidity.In addition,the thermal stability of the device was significantly enhanced,with the encapsulated device retaining 80% of its original PCE after aging at 85°C,while the PCE of the unencapsulated device decreased to only 40% of its original value after 50 hours.Therefore,the PEI encapsulation layer can effectively alleviate the penetration of moisture from the environment into the perovskite film,improve the stability of the perovskite film to humidity,and enhance the internal thermal stability of PSCs devices,thus increasing their long-term lifespan.