Electrosprayed TiO₂nanoporous hemispheres for enhanced electron transport and device performance of formamidinium based perovskite solar cells

Abstract

Titanium dioxide (TiO) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO nanoparticle (NP) suspension solution. The resulting TiO NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO layer for FAMAPb(IBr) based perovskite solar cells (PSCs). By varying the TiO NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO NHS distribution densities. The optimized PSC employing TiO NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a J of 23.8 mA cm, a V of 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 TiO NHS based PSC than that in the TiO NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO NHSs a promising electron transport material for efficient photovoltaic devices.

Performance Enhancement of Tri‐Cation and Dual‐Anion Mixed Perovskite Solar Cells by Au@SiO2 Nanoparticles

“…The device performance improvement may derive from the enhanced charge carriers collection and transportation within it. To study the photogenerated free carrier behavior in the Au‐0 and Au‐2 devices, small perturbation TPV was utilized to observe the fast decay component occurrence within the system . Thus, we operated complementary small perturbation TPVs by using a white light source to vary the back illumination level and a ns‐pulsed 532 nm neodymium‐doped yttrium aluminium garnet (Nd/YAG) laser to induce the small voltage perturbations.…”

“…Charge carriers mobilities in this device were also studied with TOF photoconductivity technique at room temperature . By simply changing the applied voltages of the device, the electron and hole transit time can be obtained separately.…”

“…Figure a,b shows the log–log plots of the TOF transits spectra for free holes and electrons, respectively (the full spectra of linear holes and electrons plots can be found in Figures S10 and S11, Supporting Information). Transit times can be obtained from the log–log plots of the TOF spectra and the charge mobility (μ) in the system can be further calculated with the relation μ = d 2 / Vt T , where d is the hole or electron transporting lengths before reaching the electrodes (Au for holes and FTO for electrons), V is the applied voltage, and t T is the transit time. As can be seen from Figure c, the calculated hole mobility in the perovskite/spiro‐OMeTAD [2,2′,7,7′‐tetrakis( N , N ‐di‐ p ‐methoxyphenylamine)‐9,9′‐spirobifluorene] heterojunction (700 nm thick) at ambient condition is ≈9.6 × 10 −3 cm 2 V −1 s −1 , which is nearly one order of magnitude higher than that in the Au‐0 PSC (≈10 −3 cm 2 V −1 s −1 ), with an external applied electric field of 1.43 × 10 4 V cm −1 in the Au‐2 device.…”

“…Although the mixed perovskite light absorbers can work effectively in some efficient PSCs, there is still space for PCE improvement since the light distribution within the perovskite light‐absorbing layer can be further optimized and the electrons and holes transporting mobilities in the system are mismatched . By in‐situ enhancing of light absorption through various metal nanoparticles (NPs), approaching or even surpassing the Shockley−Queisser limit for 1 sun condition could be achieved within this mixed PSCs .…”

Highly Oriented Electrospun P(VDF‐TrFE) Fibers via Mechanical Stretching for Wearable Motion Sensing

“…To construct piezoelectric polymer fibers, electrospinning, as a representative template‐free method, is a versatile technique to produce extended length of fiber‐shaped structures with a number of advantages such as large surface area, tunable surface morphologies, and enhanced mechanical performance . With electrospinning, when the droplet of polymer solution is charged by high applied voltage, the liquid droplet is pulled into a thin fiber and then collected by the grounded electrode.…”