High-Performance Inorganically Connected CuInSe₂ Nanocrystal Thin-Film Transistors and Integrated Circuits Based on the Solution Process of Colloidal Synthesis, Ligand Exchange, and Surface Treatment

Abstract

Nanocrystal (NC) CuInSe2 thin-film transistors (TFTs), consisting of nontoxic and relatively abundant elements, have great potential in environment-friendly and low-cost electronic devices. However, the high-performance CuInSe2 NC TFTs reported so far utilize toxic compounds, such as CdSe and hydrazine, which often require tedious and complex procedures. TFTs using directly synthesized CuInSe2 NCs as channel layers exhibit promising device performances but are still not comparable to the counterparts of cadmium and lead chalcogenide-based NCs. In this work, an efficient solution-based colloidal synthesis and ligand-exchange process have been developed to effectively remove bulky surfactant ligands from CuInSe2 NCs and produce unique inorganically connected NCs through metal-sulfide bonding using simple metal-free chalcogenide compounds. Such inorganically connected CuInSe2 NC thin films, combined with surface treatment, substantially affect charge transport through trap states and tunneling transport mechanism. The carriers tunneling through the barrier between neighboring NCs with much shorter interparticle distances significantly enhance electronic coupling and improve the electrical transport properties. CuInSe2 NC TFT exhibits the electrical performance with a mobility of 9.6 cm2/(V s), on/off current ratio over 104, and negligible hysteresis at low operating voltages, comparable to those for state-of-the-art II–VI- and IV–VI-type NC TFTs. As a proof of concept, the CuInSe2 NC TFTs are used as building blocks of integrated inverters to demonstrate their promise for low process temperature-fabricated NC circuits.

Colloidal Synthesis of P‐Type Zn3As2 Nanocrystals

“…These results strongly suggest that 1) the insulating long-chain organic ligands (OLAM) were substantially removed, and 2) the zinc halide ligands effectively passivated the surface defects of the NCs. [59,60] By replacing the long and insulating OLAM with short inorganic ligands, the intercore distances between the NCs could be reduced, and the surface defects acting as trap sites could be passivated, resulting in improved channel conductance. Compared to the ZnBr 2 and ZnI 2 ligands, the ZnCl 2 ligands showed significantly lower oncurrents and hole mobilities.…”

General synthesis of ionic-electronic coupled two-dimensional materials

“…[14][15][16][17][18], and we conducted HRTEM and energy-dispersive spectroscopy (EDS) to characterize the 20 kinds of as-grown AMX 2 compounds (Supplementary Figs. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. The synthesized AMX 2 compounds exhibit good agreement with the expected phases and show high crystalline quality.…”

“…Thus, introducing the superionic conductivity [16][17][18] , multiferroics 19,20 , and magnetism 21 properties within the AMX 2 . Meanwhile, the multielement characteristic and various atomic structures give the AMX 2 rich band structures 19,22,23 , making the AMX 2 compounds excellent systems for studying intrinsic coupled ionic-electronic properties. While a few demonstrations of the synthesis of 2D AMX 2 have been reported 16,24 , the fabrication of most of these compounds remains elusive, hindering their exploration and application.…”

Phase-Controlled Synthesis and Phase-Change Properties of Colloidal Cu–Ge–Te Nanoparticles

“…PCM layers are commonly deposited as thin films by sputter deposition or physical/chemical vapor deposition, which are intrinsically highly specialized, material-specific, and expensive process techniques . In this regard, solution-based processing has earned a reputation as a relatively straightforward and inexpensive approach for materials screening, offering a feasible and fast alternative to create new PCM compositions. − Specifically, colloidal hot-injection method has been proven to be a rapid and convenient way to produce nanoscale chalcogenide PCM materials, such as GeTe. − For example, excellent size control has been achieved for binary GeTe nanoparticles, offering the advantage of size-dependent tunability of crystallization temperature . Synthesizing ternary and multicomponent PCM nanoparticles, however, comes with the challenge of simultaneous size and composition control, which is exacerbated when combining aliovalent elements. , The use of elemental precursors with different reactivities is often required to engineer ternary nanoparticles, limiting the extent and precision of composition control.…”