Organic semiconductors are thin, flexible materials that already underlie many consumer displays, and researchers now report a strategy that allows these materials to both efficiently emit light and harvest energy in the same device. Their work focuses on multifunctional organic components that can act as both organic light-emitting diodes and organic photovoltaic elements without sacrificing performance in either role.
In conventional designs, light emission and energy generation place conflicting demands on excitons, which are bonded pairs of electrons and positively charged holes. Efficient electroluminescence requires excitons to recombine robustly to produce photons, while efficient photovoltaics requires excitons to quickly dissociate into free charges that can be collected as electric current. This trade-off has long been seen as a fundamental barrier to realizing high-performance organic dual-function devices.
A team led by Professor Hirohiko Fukagawa of the Center for Frontier Science at Chiba University, Japan, tackled this problem by manipulating the energy states of excitons with thermally activated delayed fluorescent materials with multiple resonances. In a paper published online on December 7, 2025 in Volume 17 of Nature Communications, they describe how carefully selected MR TADF compounds, used as both light emitters and light absorbers, form donor-acceptor interfaces with unusually low exciton binding energies.
Exciton binding energy, Eb, measures how tightly the electron and hole are connected at the molecular level. By tuning the material system so that Eb becomes small at the donor-acceptor interface, the researchers achieved devices with minimal voltage drop and near-ideal power generation behavior, while still maintaining strong light emission. Professor Fukagawa notes that devices with smaller Eb exhibit very little electrical loss, which supports efficient photovoltaic operation.
The team also used control over Eb to tune the emission color produced by the devices. When Eb remained relatively large, the devices emitted yellow light originating from charge-transfer excitons, in which the electron and hole occupied adjacent molecules across the donor-acceptor boundary. When Eb was decreased, the emission switched to blue light from the MR TADF donor itself, allowing color control by adjusting the interface composition.
By optimizing the interfacial materials and their energy levels, the researchers fabricated green- and orange-emitting multifunctional devices that maintained high performance in both operating modes. These devices achieved an external quantum efficiency for light emission of more than 8.5 percent, while the energy conversion efficiency remained around 0.5 percent, outperforming previous reports of similar dual-function structures. According to Professor Fukagawa, the observed device efficiency of 8.5 percent, taking into account the intrinsic emission efficiency of 44 percent of the green emitter and an estimated light extraction efficiency of 20 percent, approaches the theoretical limit with virtually no electrical loss.
Additionally, the group demonstrated what they describe as the first power-generating blue OLED with multifunctional capabilities. Achieving blue emission while simultaneously extracting usable electrical energy is considered particularly challenging, so this result marks an important milestone in multifunctional organic optoelectronics.
The team envisions a new generation of self-powered electronics that integrates energy harvesting directly into luminous surfaces. Potential near-term applications include display panels and lighting tiles that recover energy from ambient lighting, such as smartphone screens that help charge their own batteries, both indoors and outdoors. The same approach could support visible light communications systems in which panels generate power during bright conditions and then use the stored energy to transmit data at night.
Looking ahead, the researchers see their design strategy as a step toward fully integrated films that combine various electronic and photonic functions into one organic stack. Such all-in-one layers could enable battery-free sensors and wearable devices that operate autonomously by harvesting light from their environment. The group also links this concept to the broader goal of a carbon-neutral society, in which improved energy efficiency in everyday electronics helps reduce overall energy demand.
The study, titled “A Pathway to coexistence of electroluminescence and photovoltaic conversion in organic devices,” lists authors Taku Oono, Yusuke Aoki, Tsubasa Sasaki, Haruto Shoji, Takuya Okada, Takahisa Shimizu, Takuji Hatakeyama and Hirohiko Fukagawa from Japanese institutions including NHK Science and Technology Research Laboratories, Tokyo University of Science, Kyoto University and Chiba University. The authors declare that they have no competing interests.
The project received support from the Japan Science and Technology Agency through the CREST program under grant number JPMJCR22B3, and from the Japan Society for the Promotion of Science KAKENHI program under grant number 24K23071. The work illustrates how targeted public investments in advanced optoelectronic materials can accelerate the emergence of practical multifunctional devices.
Research report:A path towards the coexistence of electroluminescence and photovoltaic conversion in organic devices
