Move over Wi-Fi, new phototransistor opens opportunity to share data with light

Wi-Fi could be getting some faster competition, as light fidelity (Li-Fi) opens new opportunities for networked, high-speed communication. To achieve this goal, phototransistors are indispensable, but current designs are too slow, limiting the optical communication speed.

Chen-Yang Tzou et al. reported a new architectural approach to a phototransistor that has the flexibility to switch quickly between an insulator and a conductive state so it can function as a logical device. The new design is incredibly fast and only consumes energy as it switches between states.

“The demand for fast calculation, high-speed data transmission and wireless communication will never be satisfied by Wi-Fi alone,” said Tzou. “The new structure we developed [for the phototransistor] is beneficial not only for high-speed communication but also for circuit miniaturization and energy saving.”

The researchers fabricated a device that consists of a bi-stable resistive random access memory (RRAM) used in tandem with an organic solar cell (OSC). They demonstrated that the output current from the phototransistor could be controlled electrically or optically with a response time of 3 µs, far exceeding other phototransistor devices currently available.

“Our innovative phototransistor concept not only offers a wide variety of ways for operation but also for a very wide range of applications,” Tzou said. “The combination of RRAM and OSC is just one of the ways to prove our concept.”

According to Tzou, the new phototransistor design might be incorporated into commercial products such as optical information encryption, communication devices and communication security.

Source: “An ultra-fast two-terminal organic phototransistor with vertical topology for information technologies,” by Chen-Yang Tzou, Shu-Yi Cai, Chen-Yang Tseng, Chi-Yuan Chang, Shu-Yuan Chiang, Cing-Yu Jiang, Yao-Hsuan Li, Jing-Meng Ma, Yu-Ming Liao, Fang-Chi Hsu, and Yang-Fang Chen, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5087980 .