The Study Of Metal Oxide Materials As Electron Transport Layer In Perovskite Solar Cells

Since the first report of utilization in photovoltaics in 2009,hybrid organic-inorganic perovskite solar cells?PSCs?have aroused increasing attention around the world.PSCs emerge as the most promising photovoltaic devices in commercialization,owing to their unique properties,including simple production process,low cost and impressive high efficiency.In just a few years,the power conversion efficiency?PCE?of PSCs has boosted from 3.8%to over 22%.The conventional planar PSCs are usually composed of an anode?FTO or ITO?,an electron transport layer?ETL?,a perovskite light-absorbing layer,a hole transport layer?HTL?,and a cathode?Au or Ag?.The ETL and the perovskite layer play a critical role in the performance of PSCs.The quality of perovskite greatly affects the absorption of incident light and the generation of the photon-induced carriers,directly determining the PCEs of devices.The ETL has impact on the electron extraction and transport from perovskite layer to the anode as well as suppression of the recombination with holes.Currently,titanium oxide?TiO₂?is the most commonly material used as the ETL,resulting from its high stability,inherent transparency,appropriate energy level and low cost.However,its low electron mobility and defects at the surface result in undesirable electron-hole recombination which hinders the enhancement of PSCs performance.Accordingly,it is essential to optimize the quality of perovskite and develop promising metal oxide materials to replace TiO₂ as ETLs,which is beneficial to further enhancement of the performances of PSCs.1)At the beginning of the paper,we introduce the development and working principle of PSCs briefly.2)We optimize the quality of perovskite by doping chloride ion in one-step method.The effect of spin-coating speed and annealing time on the perovskite has been systematically illustrated.To form a high-crystallized perovskite film,chlorobenzene has been dropped during the spin-coating procedure.Finally,a compact,flat and pinhole-free perovskite film with high coverage is obtained.The two-step method has been also introduced in this chapter.3)We firstly develop the spin-coated Nb₂O₅ films as ETLs for efficient planar PSCs.By control the precursor concentration and annealing time of Nb₂O₅,we successfully enhance the photovoltaic performance of PSCs,eventually yielding a champion PCE of14.82%.The desirable efficiency is attributed to high transmittance,the appropriate conduction band position of Nb₂O₅,increased charge transport,and diminished charge recombination.4)We for the first time introduce the spin-coated Ta₂O₅ film in the planar PSC.The impact of the precursor concentration,spin-coating speed and times of Ta₂O₅ on the cell performance are systematically investigated.The champion device fabricated with the optimized Ta₂O₅ films achieves a PCE as high as 11.12%.