Quantum tunneling proton boosts energy transfer in lab-scale light experiment

A Chinese research team found that shuttling a single proton speeds and sharpens energy transfer in quantum dots, with prospective uses in solar cells.

Researchers at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, led by Professor Kaifeng Wu, reported a mechanism they call proton shuttle-assisted triplet energy transfer, or PS-TET. The work, by Zhaolong Wang, Jingyi Zhu, and Wu, was published in Nature Materials (volume 25, issue 7, page 1190).

The team watched energy move from ZnSe-based colloidal quantum dots to phenol-pyridine acceptor molecules attached to their surfaces. When the dots absorb light, a hole moves from the dot to the phenol while a proton shifts from phenol to pyridine; then an electron transfers to the phenoxyl radical and the proton returns to its origin. Compared with a version lacking the shuttle, this proton motion increased both the speed and efficiency of the transfer. Because the rate changed little with temperature, the researchers concluded the proton moves by quantum tunneling rather than a heat-driven jump, a reading supported by calculations of proton vibrational wavefunction overlaps.

Controlling triplet formation matters because that step governs efficiency in solar cells, lasers, and catalysis. The researchers suggest a proton shuttle could be added to boost triplet formation or removed to suppress it, giving a design lever over how light energy is routed. Cheaper, more efficient light harvesting is one route to less costly energy.

This is a laboratory study. No commercial device has been built, and the uses in solar cells, lasers, and catalysis remain prospective. Watch whether the mechanism holds up in materials beyond ZnSe dyads and whether the efficiency gains survive scale-up.

Source: ScienceDaily