Room‐Temperature Meniscus Coating of >20% Perovskite Solar Cells: A Film Formation Mechanism Investigation

Abstract

Perovskite solar cells (PSCs) are ideally fabricated entirely via a scalable solution process at low temperatures to realize the promise of simple manufacturing, low‐cost processing, compatibility with flexible substrates, and perovskite‐based tandem solar cells. However, high‐quality photoactive perovskite thin films under those processing conditions is a challenge. Here, a laminar air‐knife‐assisted room‐temperature meniscus coating approach that enables one to control the drying kinetics during the solidification process and achieve high‐quality perovskite films and solar cells is devised. Moreover, this approach offers a solid model platform for in situ UV–vis and microscopic investigation of the perovskite film drying kinetics, which provide rich insights correlating the degree of supersaturation, the nucleation, and growth rate during the kinetic drying process, and ultimately, the film morphology and performance of the solar cell devices. Manufacturing friendly, antisolvent‐free room‐temperature coating of hysteresis‐free PSCs with a power conversion efficiency of 20.26% for 0.06 cm2 and 18.76% for 1 cm2 devices is demonstrated.

Bio-inspired vertebral design for scalable and flexible perovskite solar cells

“…The effects on nucleation sites and nucleation rate can be well described by using the LaMer diagram ( Fig. 2c) [45][46][47][48] , which demonstrates three distinct regimes of nucleation and crystal growth for perovskite precursor solution on flexible substrates: (I) pre-nucleation, (II) nucleation and crystallization growth and (III) crystallization (see detailed explanations about crystallization kinetics in Supplementary Note 4). From the above three stages, the best way to optimize the quality of flexible perovskite films is to reduce the nucleation sites appropriately and extend the grain growth process, which has been verified by the Arrhenius type equations (Supplementary Eqs.…”

A prenucleation strategy for ambient fabrication of perovskite solar cells with high device performance uniformity

“…The nucleation and growth processes are highly dependent on the nucleation and growth rates of the intermediate, which is so critical that could allow a topotactical conversion to high-quality perovskite films. According to the Burton-Cabrera-Frank (BCF) theory, the number of crystallites per unit area (N) can be expressed as [23][24][25] :…”

High‐Pressure Nitrogen‐Extraction and Effective Passivation to Attain Highest Large‐Area Perovskite Solar Module Efficiency

“…On one hand, the high speed nitrogen flow enables solvents to evaporate rapidly from the wet coating, quickly driving the system to a oversaturated state for homogeneous crystallization. [24] On the other hand, when the highly compressed nitrogen escapes from the outlet into the ambient, the quick gas expansion from high pressure to atmospheric pressure is expected to cause significant temperature drop (Equations (S1) and (S2), Supporting Information). As evidenced by Figure S5, Supporting Information, the low-temperature nitrogen flow is expected to effectively decrease the local temperature at the coating surface from 25.0 °C to 12.9 °C, leading to oversaturation for uniform crystallization.…”