Researchers from South Korea’s Daegu Gyeongbuk Institute of Science and Technology and the Korea Institute of Science and Technology have shown that a natural antioxidant molecule can act as a self-regenerating shield for perovskite solar cells, enhancing operational stability. Drawing inspiration from taurine – a sulfur‑containing amino acid abundant in octopus and squid – the team introduced an ultrathin taurine layer at the buried interface between the tin‑dioxide electron‑transport layer and the perovskite absorber, where oxygen‑driven degradation usually begins.
Devices incorporating this antioxidant interlayer reportedly retained 97% of their initial efficiency after 450 hours of continuous illumination at 65 °C, far outperforming untreated controls.
Density-functional-theory calculations, paired with spectroscopic experiments, revealed how taurine provides protection through a two-stage mechanism that regenerates continuously during operation.
In the first stage, taurine intercepts superoxide radicals forming at oxygen vacancies on the tin-dioxide surface. The molecule carries both a positive charge on its amino group and a negative charge on its sulfonate group, a configuration chemists call zwitterionic, meaning it bears opposite charges at different sites simultaneously. This internal charge separation electrostatically confines superoxide ions. The sulfonate hydrogen then participates in a proton-coupled electron transfer that converts superoxide into hydrogen peroxide, a far less damaging species.
The second stage addresses a downstream threat. Hydrogen peroxide reacts with additional taurine molecules, releasing peroxide ions that reduce iodine gas back into iodide ions. This matters because iodine, a primary byproduct of perovskite breakdown, readily forms triiodide under illumination. Triiodide accelerates further decomposition in a vicious cycle. By converting iodine back to iodide, taurine breaks this feedback loop.
The peroxide ions then oxidize to neutral molecular oxygen, regenerating taurine to its original zwitterionic state. This closed cycle enables continuous radical scavenging rather than one-time protection.
Multiple analytical techniques confirmed the protective effect. Transmission-electron microscopy of films exposed to simulated sunlight under nitrogen revealed macroscopic voids at the interface of untreated samples. Films incorporating taurine displayed clean, intact boundaries. X-ray photoelectron spectroscopy depth profiles detected hydroxyl species migrating deep into untreated perovskite, a chemical fingerprint of superoxide attack. Treated films showed no such infiltration. Under accelerated-aging conditions involving ultraviolet light in an ozone-rich atmosphere, taurine-treated samples retained roughly seven times more of the original perovskite phase than controls after 90 minutes.
Beyond radical scavenging, taurine acts as a molecular bridge linking the two materials it separates. Its amino group forms hydrogen bonds with iodide ions in the perovskite lattice. Its sulfonate group coordinates with uncoordinated tin atoms and fills oxygen vacancies on the tin-dioxide surface. This dual anchoring reduces the density of electronic trap states, defect sites that capture charge carriers and cause them to dissipate energy as heat rather than contribute to electrical current.
Electrical measurements quantified these benefits. The trap-filled limit voltage, an indicator of defect density, dropped from 0.85 V in control devices to 0.50 V in treated devices. Electron mobility in the tin-dioxide layer nearly doubled, climbing from 8.6 × 10⁻⁸ to 1.4 × 10⁻⁷ cm² V⁻¹ s⁻¹.
Photoluminescence studies showed that taurine treatment nearly doubled the average carrier lifetime in perovskite films, confirming suppressed energy losses. Ultraviolet photoelectron spectroscopy revealed that taurine shifted the conduction-band minimum of tin dioxide upward, improving energy-level alignment with the perovskite and easing charge extraction.
The best-performing device achieved a power-conversion efficiency of 24.8%, slightly below current laboratory records but with markedly improved stability, along with an open-circuit voltage of 1.18 V and a fill factor of 83.7%, a metric indicating how closely a cell approaches its theoretical maximum power.
Long-term stability tests proved equally compelling. Under maximum-power-point tracking with encapsulated devices operating in ambient air under one-sun illumination, treated devices retained 80% of initial efficiency after 130 hours. Control devices crossed the same threshold after just 23.6 hours, a more than fivefold difference in operational lifetime.
The findings suggest that beyond encapsulation, there are additional methods that can help deliver the durability commercial deployment demands. According to the team, oxygen species embedded in metal-oxide transport layers, or trapped during fabrication in air, initiate degradation that sealing cannot prevent. Engineering the buried interface with compounds that neutralize reactive oxygen offers a complementary defense, and the fact that a naturally occurring antioxidant abundant in common seafood can fulfill this role opens a path toward biologically inspired strategies in photovoltaic materials design.
