Korea University: Flexible Solar Cell Integrated with Memory
The research group led by Professor Kim Tae-geun of the School of Electrical Engineering of the College of Engineering successfully developed a memristive organic solar cell (MemOSC) that integrates the memory and learning functions in a single chip by using a 2D titanium carbide (Ti3C2Tx) MXene-based multilayer (Ti3C2Tx MXene/Ag/ Ti3C2Tx MXene) flexible transparent electrode.
Organic solar cells (OSC) have gained much attention due to their low production cost, low weight, mechanical flexibility, and ease of large-area fabrication. Studies have been actively conducted to grant learning capabilities to the devices. Meanwhile, developing an electrode that has low sheet resistance, transparency, and high mechanical stability is essential for improving the performance of all photovoltaic devices, including solar cells. Currently, conventional indium tin oxide (ITO)-based electrodes are used commercially due to their high transmittance and high conductivity, but they have the drawbacks of low mechanical flexibility and the high price of the constituent indium.
The research group doped Zn nanoparticles onto the surface of an electrode with a Ti3C2Tx MXene/Ag/Ti3C2Tx MXene multilayer structure fabricated by spin coating and sputtering. In this way, the group successfully developed a flexible transparent electrode featuring a low sheet resistance of 9.7 Ω sq-1, a high transmittance of 84%, stable properties even after a 2,000-cycle bending test, and an easily controlled electrode work function. The memristive organic solar cell (MemOSC) equipped with the developed electrode exhibited a power conversion efficiency of 13.86% and sustained stable photovoltaic performance even after hundreds of switching cycles. The MemOSC also demonstrated excellent memory performance characterized by a low operating voltage of 0.06 and -0.33 V, a high ON/OFF ratio (103), stable endurance performance (4×103), and excellent memory retention properties (>104 s).
The results showed that the 2D MXene-based multilayer electrode structure functions well as the flexible transparent electrode of OSCs and that it can function as electrically readable nonvolatile memory. In addition, energy harvesting and artificial synaptic (memory and learning) functions may be integrated into the structure in the future to produce integrated energy devices and systems.
The research was supported by the Research Leader Program funded by the Ministry of Science and ICT and the National Research Foundation of Korea (NRF). The article was published in Advanced Science [IF:17.521, JCR, Journal Citation Reports: top 5.94%], a globally renowned journal, on May 3, 2023.