Researchers from China's Northwestern Polytechnical University and Xijing University have developed an ambient laser shock annealing (LSA) strategy to precisely control crystallization kinetics in quasi-two-dimensional (Q-2D) perovskites, enabling solar cells that combine high efficiency with markedly improved stability.
The approach leverages an ultrafast laser pulse to simultaneously deliver thermal energy and a mechanical shock wave, initiating crystallization through a transient but stable PbI₂ intermediate phase. This coupled photothermal–mechanical process unfolds on the timescale of the laser pulse and generates a peak pressure of 8.91 GPa. Notably, the induced stress field remains highly uniform, with attenuation below 5% across a 500 nm film thickness, allowing controlled structural evolution throughout the perovskite layer.
This precise kinetic control addresses a central limitation of Q-2D perovskites: their sensitivity to crystallization pathways. In conventional processing, rapid solvent evaporation can induce excessive supersaturation, leading to dense nucleation and disordered small grains, while slow thermal annealing often promotes phase segregation and loss of volatile organic components. In contrast, LSA rapidly traverses the critical decomposition temperature window, enforcing a synchronized reaction among precursors and preserving stoichiometric uniformity.
At the microstructural level, the LSA-induced stress and thermal profile promote lateral grain growth, preferential orientation (texturing), and reduced dipole disorder. The resulting films exhibit enlarged grains and improved structural coherence, along with reduced defect densities. These features directly translate into improved optoelectronic performance by suppressing non-radiative recombination and facilitating vertical charge transport - particularly important in Q-2D systems where organic spacer layers typically hinder carrier movement.
Devices fabricated using this method achieved a power conversion efficiency (PCE) of 20.41%. This performance was supported by enhanced carrier transport enabled by aligned organic cations and improved interfacial contact arising from lattice compression during the shock process.
In addition to efficiency gains, the LSA-treated films show enhanced mechanical robustness and environmental stability. Reinforced inorganic-organic interactions increase the Young’s modulus to 28.38 GPa, indicating a mechanically stiffer and more durable film. This improved mechanical integrity helps maintain structural and electronic properties over extended operation.
Overall, the study establishes a clear link between ultrafast, pressure-assisted crystallization to optimized microstructure and device performance. By combining controlled thermal dynamics with shock-induced strain engineering, LSA provides a well-defined and scalable pathway for advancing Q-2D perovskite solar cells toward both higher efficiency and long-term stability.
