Fabricating High‐Efficient Blade‐Coated Perovskite Solar Cells under Ambient Condition Using Lead Acetate Trihydrate

Abstract

Heat‐assisted blade‐coating (HABC) technique can be applied for scalable production of perovskite solar cells (PSCs). With the current setups, HABC is not applicable in ambient atmosphere due to the adverse impact of humidity on perovskite films. Here, a modified HABC method is reported to achieve high quality perovskite films under harsh ambient conditions. By using lead acetate trihydrate (PbAc2 · 3H2O) as the lead source, a rapid low‐temperature, short time annealing treatment is discovered. It is found that a small amount of hydrate water in PbAC2 · 3H2O lead source lead to dense and oriented nuclei at the blade‐coating stage. The concomitant MAPbI3 · xH2O on the surface and grain boundaries of perovskite films isolates the moisture in ambient during the annealing process, melts to form a quasi‐liquid nutrition pool for the cultivation of MAPbI3 grain domains via Ostwald ripening. The as‐prepared perovskite films consist of large grain domains of up to 100 μm, which are highly orientated. Based on these films, the conversion efficiency of PSCs reaches 15.8 ± 0.6%, a jump of nearly 40% compared with that of PbAc2‐sourced devices (11.4 ± 1.0%). The robust strategy presented here is a significant contribution towards scalable production of high efficiency PSCs under ambient condition.

Scalable Deposition Methods for Large‐area Production of Perovskite Thin Films

“…Left: Comparison of one-step and two-step deposition on slot-die coating and spin coating. 2019, 2, 119-145 morphology of blade-coated perovskites using a lead acetate route with controlled nucleation and growth temperatures [91] ; top right shows morphology changes through solution doping of MACl, used to blade coat large grains [85] ; and bottom shows growth differences at different thicknesses using MACl as a growth modifier. [77] Right bottom: comparison of one-step slot-die and spin coating, with homogeneous growth.…”

“…All others are maximum. [91] (Top right) Blade-coated triple-cation, double-halide films with MACl as a grain growth modifier. The crystal growth process is driven by the processing parameters such as the deposition chamber pressure and substrate temperature as well as substrate material surface properties and morphology.…”

A Matter of Drying: Blade‐Coating of Lead Acetate Sourced Planar Inverted Perovskite Solar Cells on Active Areas >1 cm2

“…One promising deposition technique for larger areas is blade coating, being compatible to roll‐to‐roll processing and having been successfully employed for absorber layers in PSC . Still, even for devices in which the perovskite absorber layer (alone or together with other functional layers) is deposited via blade coating, there is only a small number of published results for PSCs with active areas ≥ 1 cm 2 . In a very recent publication, slot‐die coating of the perovskite layer in air was employed in a roll‐to‐roll process, which is intrinsically a large area fabrication technique.…”

“…A good overview of results regarding the application of blade coating in the fabrication process of both small area and larger area PSCs is given in a recent review by Zi et al Almost exclusively, all processes rely on lead iodide as source for the absorber layer, even though other non‐halide precursor materials, especially lead acetate, are known to yield smooth and pinhole‐free perovskite layers in a simple one‐step process . Kong et al recently have reported on the (to the authors’ knowledge) first application of lead acetate for blade coated perovskite solar cells . During the perovskite film preparation, control of the drying dynamics and associated parameters like nucleation, crystal growth, dewetting of the substrate and pinhole formation is generally found to affect the performance of final devices.…”

“…Too slow drying of the deposited precursor wet films, for example, has been found to result in the formation of so called coffee ring patterns, leading to rough and inhomogeneous perovskite layers . Controlled drying and crystallization of blade coated perovskite films is usually established by temperature control, treatment of the freshly prepared films with an antisolvent like diethylether or toluene or addition of high‐boiling point solvents to the precursor solution . Another option is applying an air‐ or nitrogen flow to assist the drying of freshly prepared layers.…”