Perovskite solar cells (PSCs) have emerged as one of the most promising candidates for next-generation photovoltaics. However, precisely controlling the crystallographic orientation of perovskite films remains a key challenge. Randomly oriented grains often lead to uneven charge transport and accelerated degradation, limiting both the performance and stability of PSCs. Achieving a uniform and well-defined crystal orientation is therefore crucial for developing high-efficiency and durable devices.
Addressing this challenge, a research team led by Prof. LI Can from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) developed a solvent–additive cascade regulation (SACR) strategy that enables the controlled growth of single-oriented perovskite films. Their findings were recently published in Energy & Environmental Science.
The team has been systematically exploring how crystal facet orientation affects the optoelectronic properties of perovskite materials. They previously developed methods to induce highly (111)-oriented perovskite films, achieved ordered stacking of (001)-oriented crystals, and revealed the crucial role of facet distribution in determining device performance.
In the new study, the researchers demonstrated that solvent composition and additive chemistry cooperatively determine the crystallographic orientation of perovskite films during solution growth. The solvent composition governs the formation of specific intermediate phases that serve as structural templates for nucleation. For example, the N,N-dimethylformamide (DMF) /dimethyl sulfoxide (DMSO) system forms PbI2·DMSO adducts favoring (111)-facet nucleation, whereas the DMF/N-methyl-2-pyrrolidone (NMP) system produces PbI2·(DMF/NMP) complexes that promote (100)-facet growth. Meanwhile, cyclohexylamine (CHA) and cyclohexylammonium iodide (CHAI) act as facet-selective additives, modulating facet-dependent crystallization kinetics through selective adsorption or chemical reactions.
Moreover, the researchers establish a direct link between solvent coordination, facet-dependent growth dynamics, and film orientation. Using the SACR strategy, they achieved precise orientation control, producing single-oriented perovskite films with distinct performance advantages: (100)-oriented devices achieve a power conversion efficiency of 25.33% with enhanced charge transport, while (111)-oriented devices exhibit superior environmental stability—retaining over 95% of their performance after 2,000 hours of ambient exposure.
"Our solvent–additive cascade strategy bridges solvent chemistry and crystal growth dynamics, enabling controllable orientation in perovskite films," said Assoc. Prof. LIU Jiewei, co-corresponding author of the study. "This finding deepens our understanding of facet-driven performance and offers new opportunities to design more efficient and stable perovskite solar technologies."