(765f) Integrated Logic Gate Devices Fabricated Using Non-Toxic CuInSe2 Quantum Dots

Copper indium diselenide (CuInSe₂) quantum dots (QDs) are an environmentally friendly alternative to heavy-metal based QDs for solution-processed devices. The key to using chemically synthesized QDs in electronic circuits is understanding charge-carrier transport in QD films, which is known to be influenced by factors such as surface chemistry, inter-dot coupling and doping levels. Here we study charge carrier transport in solids of CuInSe₂ QDs exposed to various types of surface treatments and explore their applications in solution-processed electronic devices such as field effect transistors (FETs) and logic gates. We show that using appropriate surface modifications, the QD-film transport polarity can be tuned from p-, to ambipolar, and n-type. Our initial findings suggest that as prepared CuInSe₂ QD films have a high density of surface defects, which, however, can be dramatically reduced by in-filling via atomic layer deposition (ALD) with a-Al₂O₃. The ALD-treatment also significantly increases carrier mobilities, reduces the free carrier density and improves film’s stability. Using ALD-in-filled QD solids, we demonstrate high performance n-channel FETs with good electron mobilities (up to ~1 cm²/Vs) and the on/off ratio of ~10⁴. Furthermore, we fabricate logic gate devices such as complementary metal-oxide-semiconductor inverter and negative AND (NAND) gate digital circuits by combining unipolar p- and n-type CuInSe₂ QD-films. These device demonstrations point towards a considerable potential of these environmentally friendly QD materials for applications in solution-processible electronics.