Organic light-emitting diodes (OLEDs) are becoming increasingly popular due to their high-resolution, full-color display capabilities. These devices, used in foldable mobile phones and ultrathin television sets, provide flexibility, self-lighting, low weight, thinness, superior contrast, and low voltage displays.

OLEDs consist of multiple layers of organic ultrathin films sandwiched between electrodes, each with specific functions inside the device. However, during operation, charge accumulation and light emissions may occur at the organic layer interfaces, potentially limiting the device’s lifespan and efficiency.

To address this issue, Professor Takayuki Miyamae and his team from Chiba University in Japan used a sophisticated spectroscopic technique called sum-frequency generation (SFG) to study the charge behavior and vibrational structure at different interfaces inside OLED devices. This study, published in the Journal of Materials Chemistry C, offers insights into how charges accumulate and change at these interfaces under different operating conditions.

By using electronic SFG spectroscopy on three different types of multilayer OLED devices, the researchers were able to identify spectral changes induced by charge behavior and structure at the interfaces. The study revealed how the intensity of spectral signals changed when applying voltage to the devices, shedding light on the internal charge flow and light emission characteristics.

Furthermore, the team found that by applying square-wave pulse voltages and introducing specific materials into the OLED devices, they could manipulate the emission position, color, and shape of the light emitted. This innovative research helps material scientists design OLEDs with improved lifetimes, energy efficiency, and cost-effectiveness, paving the way for the widespread adoption of ultrathin organic devices in everyday life.