Fabrication Of Highly Efficient TiO₂-Nanorod-Array-based Perovskite Solar Cells

In recent years,perovskite solar cells have attracted tremendous attention because of their facile fabrication process and low cost.The certified efficiency of perovskite solar cells has reached 22.7%.The TiO2 nanorod array has superior electron transport performance,which can be applied as efficien electron collection layer to perovskite solar cells.Herein we report the fabrication of highly-efficient,hysteresis-free perovskite solar cells with great stability based on TiO2 nanorod arrays.Meanwhile,the growth of TiO2 nanorods with different preparing conditions and the preparation of high-quality perovskite films were also discussed.First,the optimization of the seeding layers for TiO2 nanorod arrays was studied.Spin coating method,and atomic layer deposition(ALD)method were applied to prepare the seeding layer,respectively.The influence on the morphology of the seeding layer was explored by adjusting the concentration of spin-coating precursors and by the ALD cycles.Solvothermal method was used to prepare the TiO2 nanorod array on the seeding layer,and the impacts of different seeding layers,reaction time and solvent ratio during this process were investigated in detail.Secondly,the preparation of high-quality perovskite layers doped with Cs and K was studied,usingone-step method(intermediate-anti-solvent).Based on Cs-doped perovskite solar cells,we studied the the impact of the precursor concentrations of perovskite,annealing time and temperature on the crystallite features of perovskite layers.At the same time,Uv visible absorption spectrum(Uv-vis),Photoluminescence(PL)Spectroscopy,Atomic Force Microscope(AFM),Space-Charge-Limited Current(SCLC),Scherrer's equation were applied to provide a deep insight into the phycial properties of the perovskite layers.For Cs/K-codoped perovskites,the impact of DMF:DMSO solvent ratio and spin-coating parameters on the crystallite features of perovskite filmswas also studied in detail.Finally,the effect of the perovskite absorbers on the device performance was scrutinized.Among these devices,Cs-doped perovskite solar cells annealed at 100?for 60 min,whose concentration of precursor is 1.3 M,showed a power conversion efficiency of 19.33%under the reverse scan direction and 18.81%under the forward scan direction(a difference of 2.7%between them).After 60 days stored in glovebox filled with N2,negligible decrease in power conversion efficiency could be seen.After 60 days stored in dry air atmosphere with 10%humidity,the devices could still show 95.71%of its initial efficiency.Meanwhile,the devices based on Cs/K-codoped perovskite films showed better performance in hysteresis in addition to their impressive efficiency.A power conversion efficiency of 19.68%under the reverse scan direction and 19.61%under the forward scan direction(a difference of 0.36%between them)were obtained.