Calcium titanium oxide indoor photovoltaic modules with conversion efficiencies exceeding 36%

Recently, Professor Mai Yaohua's team at the Institute of New Energy Technology of Jinan University has obtained an independent third-party certification of over 36% conversion efficiency for large-area calcium titanite indoor photovoltaic modules, the highest value reported in the world so far. The relevant research results were published in Advanced Science.

Solar cell technology using chalcogenide as the light absorbing layer has received a lot of attention in recent years. The use of photovoltaic cells for indoor low light energy harvesting can be widely used in industrial IoT, smart home and smart mobility applications, but they require a wide optical band gap to achieve high conversion efficiency. The optical band gap of chalcogenide light absorbing layers can be adjusted over a wide range, making it possible to obtain high conversion efficiency photovoltaic devices, and teams have already reported indoor chalcogenide photovoltaic cells with efficiencies in excess of 40%.

However, the high bromine (Br) content in wide bandgap chalcogenide films can easily cause phase separation phenomena and affect the device performance. Mai Yaohua's team investigated the relationship between the bandgap and the indoor photovoltaic performance of chalcogenide photovoltaic cells and found that, in addition to phase separation, Br vacancy defects in the chalcogenide photoabsorption layer are one of the main factors limiting the open-circuit voltage of the cells. Treatment with iodine(I)-rich alkali metal small molecule materials effectively solves the Br vacancy problem and improves the conversion efficiency of the device under low light. Under a TL84 light source of 1000 lux, the indoor photovoltaic module with an effective area of 12.30 cm2 obtained a conversion efficiency of 36.36% certified by an independent third party, the highest reported conversion efficiency of a calcium titanite low light module in the world.

At the same time, the team developed a prototype indoor light energy harvesting system based on the chalcogenide PV module, which achieves indoor light energy harvesting, maximum power point tracking, power and battery management, ambient temperature and humidity collection, Bluetooth communication and no-charging. In addition, the team noted that accurate testing of indoor PV cell performance and standardisation of the testing process are critical to the industrialisation of the technology.