Surface modification enabled carrier mobility adjustment in CZTS nanoparticle thin films

• Present a DFT model to estimate carrier mobility in a thin-film of nanocrystals and ligands array.
• Showed that carrier mobility has exponential dependence on ligand chain length.
• CZTS nanocrystal film (low temperature process) obtains a carrier mobility of up to 10.9 cm2/(VS).

As the essential building blocks of many electronic devices, solid state thin-films are attracting extensive interest. Soluble nanocrystals (NCs) make it possible to develop robust, low-cost, large-scale fabrication methods for thin-films. However, the organic surface ligands normally used to stabilize the NCs make those thin-films a NC–ligand complex which may possess varied electrical performance compared to a single component system. Previous models could only estimate the charge transportation characteristics in those films quantitatively by considering the capping ligands as a barrier of charges from inter-particle hopping. In this work, we demonstrated that starting from first principles density functional theory, the carrier mobility in a CZTS NC–ligand complex can be determined quantitatively, and guided by this model, we developed a low-cost, low-temperature technique to fabricate CZTS thin films which have a carrier mobility of up to 10.9 cm2/(VS).

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