Optimization Of TiO₂ As Electron Transport Layer In Perovskite Solar Cells

With the decrease of fossil energy and the deterioration of environment,the energy problem and environmental problem are becoming severer and severer around the world.In order to solve both of these problems,reserchers keep seeking a kind of energy with the advantages of non-pollution and sustainability.Solar energy is becoming one of the most popular clean energies because it is highly accessible,green,abundant and renewable.As a new star in photovoltaic field,organic-inorganic hybrid perovskite material is widely applied to solar cells with the excellent photoelectric properties including big photoabsotption coefficient,suitable direct bandgap,high carrier mobility and so on.This paper mainly studies the fabrication and optimizing of perovskite solar cells?PSCs?.The contents mainly include the following three aspects:?1?The electron transport layer?ETL?,hole transport layer?HTL?and perovskite photosensitive layer were optimized successively,and the optimized structure of PSCs including FTO/TiO₂?50 nm?/CH₃NH₃PbI₃?350 nm?/spiro-OMeTAD?160 nm?/Au?80 nm?was found.In the same time,PSCs achieving over 10%power conversion efficiency?PCE?could be fabricated repeatingly.?2?The surface of compact TiO₂ layer was modified with a thin self-assembled4-Mercaptobenzoic acid?4-MBA?molecular layer and then PSCs basing on the modifited compact TiO₂ layer were fabricated.After detailed research,the PSCs with4-MBA modification showed an improvement in the stability of photocurrent and a decrease in hysteresis index.?3?The surface of compact TiO₂ layer was modified by a thin self-assembled dodecanedioic acid?DDDA?molecular layer.With modification,the conductivity of TiO₂ can be enhanced substantially and the energy alignment of PSCs can be optimized.The modification promoted electron transport and reduced electron accumulation,resulting in improvement of the short current density(J_SC)of the best device from 20.34 mA·cm^-2 to 23.28 mA·cm^-2,and the PCE increasing from 14.17%to 15.92%under AM 1.5G illumination at 100 mW·cm^-2.In the meantime,the devices with DDDA modification showed a significant improvement in light stability,keeping71%of its initial PCE value after 720 min exposure and becoming stable.