title: Electrosprayed TiO2nanoporous hemispheres for enhanced electron transport and device performance of formamidinium based perovskite solar cells.
abstract: Titanium dioxide (TiO2) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO2nanoparticle (NP) suspension solution. The resulting TiO2NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO2layer for FA0.81MA0.15Pb(I0.836Br0.15)3based perovskite solar cells (PSCs). By varying the TiO2NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO2NHS distribution densities. The optimized PSC employing TiO2NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a Jscof 23.8 mA cm-2, a Vocof 1.14 V and a FF of 0.71. Furthermore, the PSC possesses a reproducible PCE value with little hysteresis in its current density-voltage (J-V) curves. The small perturbation transient photovoltage (TPV) measurement reveals a longer free carrier lifetime within the TiO2NHS based PSC than that in the TiO2NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO2NHSs a promising electron transport material for efficient photovoltaic devices.
authors.affiliation: Department of Mechanical Engineering, National University of Singapore, Singapore 117576, Singapore. seeram@nus.edu.sg.
authors.forename: Tao
authors.initials: T
authors.lastname: Ye
authors.forename: Shaoyang
authors.initials: S
authors.lastname: Ma
authors.forename: Xi
authors.initials: X
authors.lastname: Jiang
authors.forename: Miloš
authors.initials: M
authors.lastname: Petrović
authors.forename: Chellappan
authors.initials: C
authors.lastname: Vijila
authors.forename: Seeram
authors.initials: S
authors.lastname: Ramakrishna
authors.forename: Lei
authors.initials: L
authors.lastname: Wei