A Solvent Swap Pushes Perovskite Solar Cells to Record Efficiency

Imagine the frustration of a master watchmaker. You build a mechanism more precise than anything preceding it, yet the oil used to lubricate the gears turns to grit within days. This is the reality for engineers working with perovskites. These crystals capture light with frightening efficiency, but they are chemically temperamental. To fix the microscopic defects on their surface, scientists apply a 'passivation' layer—a chemical bandage. But often, the solvent carrying that bandage ruins the cure before it can set.

For years, the standard carrier has been isopropyl alcohol (IPA). It is cheap and available. It is also a liability. This study suggests that IPA is too chemically passive. It allows the organic ammonia salts—the active healing agents—to lose protons and degrade. The medicine spoils in the syringe.

Stabilising Perovskite solar cells with acidic solvents

The research team introduced a ruthless alternative: hexafluoroisopropanol (HFIP). Unlike its predecessor, HFIP is a strong proton donor. It acts as a chemical disciplinarian. By maintaining an acidic environment, it forces the ammonia salts to retain their structure, preventing the deprotonation that typically undermines the film's stability. The difference was immediate. The passivation solution remained stable, allowing for a manufacturing process that is finally reproducible.

The physical data tells the story of this survival. Under photoluminescence testing, the films treated with HFIP glowed with significantly higher intensity. This luminosity is not just aesthetic; it is the signal of electrons moving freely, untrapped by the defects that usually plague these materials. The carrier lifetimes extended, indicating a pristine internal structure.

Then came the climax: the performance test. A device treated with this HFIP-based solution achieved a champion power conversion efficiency of 26.91% (certified at 26.88%). Perhaps more important than the peak was the endurance. After 1,000 hours of continuous operation, the cell retained 95.9% of its initial power. By simply changing the solvent, the team turned a fragile prototype into a durable contender.