From smartphones to factories and vehicles, waste heat is everywhere.Scientists are exploring ways to convert this waste heat into electricity using thin films that can be manufactured without high-temperature processing.A team of researchers from a Japanese university has now developed a new thermoelectric material with a much greater ability to generate electricity from waste heat produced by electronic devices.By adding a small amount of titanium to chromium nitride thin films commonly used in electronics, the team improved the material’s heat-to-electricity-generating performance by 250 times.”This approach could help expand the applications of thermoelectric materials and recover energy that would otherwise be lost as heat,” said Yi Shuang, assistant professor at Tohoku University.Empty spaces in existing filmsExisting technology relies on Chromium Nitride coatings because they can be easily deposited as thin films at ambient temperature and can be easily placed inside electronic systems. However, these chromium films have lower thermoelectric performance as they have too many empty spaces because of the nitrogen vacancies.To reduce the impact of these defects, the team added titanium to the chromium nitride films, which has a stronger affinity for nitrogen than chromium. This enabled more efficient energy harvesting in devices, particularly those that cannot tolerate high temperatures during the production process, the study highlighted.”By carefully controlling defects in the material, we found a way to improve electrical transport without relying on high-temperature processing,” added Shuang.Faster electron mobilityTo maximize the material’s ability to convert heat into electricity, the team carefully adjusted the titanium content in the film to between 4.6 and 9.3 atomic percent.By doing so, they maintained good electrical conductivity while also improving the material’s ability to convert heat into electricity.The process reduced the number of charge-carrying electrons, allowing the remaining electrons to move much more freely through the material. Their mobility increased by nearly 100 times, helping overcome a long-standing challenge in thermoelectric materials, where improving electrical conductivity usually comes at the expense of electricity generation from heat.It’s a bit like building a highway where fewer cars can travel much faster, so traffic flows smoothly and deliveries are made more efficiently.In the experiments, the team found that the titanium-doped film achieved a a power factor of 5.26 µW cm⁻¹ K⁻², which they noted is 250 times that of pure chromium nitride.Researchers built a prototype generator that achieved a power density of 38.0 mW cm⁻², comparable to that of existing high-performance thermoelectric materials, while producing a maximum power output of 455.8 nW at a temperature difference of 96 K.Unlike many existing high-performance thermoelectric materials, the titanium-doped chromium nitride film was fabricated at room temperature, eliminating the need for high-temperature processing.The findings were published recently in the Journal of Materials Chemistry A.