Researchers compared two common graphene-based additives and found they are not interchangeable: pristine graphene flakes (GF) behave very differently from graphene oxide flakes (GOF) when mixed with metal‑halide perovskite precursors. Metal‑halide perovskites are a family of light‑absorbing materials used in high‑efficiency solar cells. The team combined computer modelling and laboratory tests to link what happens at the atomic scale to how thin films form and how solar cells perform.

At the atomic level, density functional theory (DFT) calculations showed that graphene oxide flakes, which carry oxygen groups on their surface, bind more strongly to the perovskite lattice. That stronger binding comes with downsides: larger distortions of the crystal structure, stronger polarisation at the interface, and the appearance of localised electronic states in the band gap. By contrast, pristine graphene flakes form milder, less disruptive contacts with the perovskite. The milder interaction was seen across a wide range of perovskite compositions in the study.

The authors also used machine‑learning atomistic simulations to follow how solvated perovskite nanocrystals meet graphene in solution. Those simulations indicate that pristine graphene contacts both lead (Pb) and iodide (I) rich regions of the solvated precursors, and that this contact pattern depends strongly on the solvent used. Complementary solution spectroscopy experiments supported this picture, suggesting that GF acts as a scaffold for pre‑organized Pb/I precursor clusters. That pre‑organisation helps the material crystallise into a better film.

The material consequences showed up in devices. Adding pristine graphene flakes improved solar cell performance across tested perovskite compositions, with the strongest gains for compositions that normally have more trouble crystallising. In a mixed tin‑lead (Sn‑Pb) perovskite solar cell, the best device efficiency (power‑conversion efficiency, PCE) rose from 21.5% to 23.7% when GF was used, and the treated devices also showed improved storage stability in the experiments reported.