Abstract
Bilayer p-n heterojunctions are promising structures to construct ambipolar organic field-effect transistors (aOFETs) for organic integrated circuits. However, due to the lack of effective strategies for high-quality p-n heterojunctions with clear interfaces, the performance of aOFETs is commonly and substantially lower than that of their unipolar counterparts, which hinders the development of aOFETs toward practical applications. Herein, a one-step solution crystallization strategy was proposed for the preparation of high-quality bilayer p-n heterojunctions. A mixed solution of a p- and an n-type organic semiconductor was dropped on a liquid substrate, and vertical phase separation occurred spontaneously during crystallization to produce bilayer p-n heterojunctions composed of molecularly thin two-dimensional molecular crystals. Due to the clear interface of the bilayer p-n heterojunctions, the maximum mobility (average mobility) reached 1.96 cm2 V−1 s−1 (1.12 cm2 V−1 s−1) for holes and 1.27 cm2 V−1 s−1 (0.61 cm2 V−1 s−1) for electrons in ambient air. So far as we know, these values were the highest among double-channel aOFETs measured in ambient air. This work provides a simple yet efficient strategy to construct high-quality bilayer p-n heterojunctions, which lays a foundation for their application in high-performance optoelectronic devices.
Highlights
INTRODUCTIONOrganic p-n heterojunctions have gained considerable attention in organic electronics because they are the basic elements of various organic optoelectronic devices, such as organic lightemitting diodes (OLEDs), organic photovoltaics (OPVs), and complementary integrated circuits (CICs)
Organic p-n heterojunctions have gained considerable attention in organic electronics1–4 because they are the basic elements of various organic optoelectronic devices,5,6 such as organic lightemitting diodes (OLEDs),7,8 organic photovoltaics (OPVs),9–11 and complementary integrated circuits (CICs).12,13Ambipolar organic field-effect transistors,14,15 in which both electrons and holes can be transported, are essential for building organic integrated circuits (ICs) with high noise margin, low power consumption, and high integration density.16,17 The simplest strategy to construct an ambipolar organic field-effect transistors (aOFETs) is to use a single-component organic semiconductor as the active layer to transport both holes and electrons
Vertical phase separation occurred spontaneously during the crystallization, and bilayer p-n heterojunctions composed of 2DMCs were formed on the liquid surface
Summary
Organic p-n heterojunctions have gained considerable attention in organic electronics because they are the basic elements of various organic optoelectronic devices, such as organic lightemitting diodes (OLEDs), organic photovoltaics (OPVs), and complementary integrated circuits (CICs).. The simplest strategy to construct an aOFET is to use a single-component organic semiconductor as the active layer to transport both holes and electrons. This strategy poses a huge challenge for both material design and device fabrication. The mobilities of these aOFET devices were typically less than 10−2 cm V−1 s−1.26,27 The reason for the poor performance is that bilayer p-n heterojunctions are composed of polycrystalline thin films with rough surfaces and high density of defects, which are not conducive to the transport of charge carriers. In 2013, Fan et al. prepared organic single-crystalline bilayer pn heterojunctions from a mixed solution using the droplet pinned crystallization method Both the p-channel and n-channel of the aOFETs were composed of aligned ribbon-like crystals. Due to the clear interface of the bilayer p-n heterojunctions, the maximum mobility (average mobility) reached 1.96 cm V−1 s−1 (1.12 cm V−1 s−1) for holes and 1.27 cm V−1 s−1 (0.61 cm V−1 s−1) for electrons in ambient air, which was the highest values among double-channel aOFETs measured in ambient air
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