The ability to control the properties of a material based on its underlying building blocks is at the core of structure-property relationships within materials science. The quantum dot solid (QDS) community has revolutionized this concept through their confined-yet-coupled design, but the implementation of these design principles to other quantum-confined systems, namely 2D materials, remains an open question. Two-dimensional materials have an interesting point of comparison to colloidal nanocrystals based on their quantum-confined, size-dependent electronic structure. Research on 2D materials has expanded rapidly, with much progress in understanding charge transport and optical absorption of individual nanoflakes and, more recently, 2D heterostructures. Despite these advances, the number of studies that investigate the interactions between quantum-confined 2D flakes that are deposited in a thick film have remained limited. Understanding the extent to which quantum-confined properties are retained or lost when 2D flakes are stacked together will be crucial for their implementation as quantum-confined solids for photovoltaic and optoelectronic applications. In this work, we demonstrate the assembly of solution-processed 2D semiconductors into quantum-confined 3D architectures. Similar to QDS, we show that these films remain quantum-confined and exhibit tunable absorption profiles that are nearly identical to that of their 2D building blocks. Characterization of these films via rocking curve XRD and conductivity measurements help to (1) elucidate the influence of stacking order and flake orientation on the quantum-confined absorption properties of these 2D solids and (2) provide evidence for a quantum-confined, yet electronically-coupled material. Our work reveals an important extension of the confined-yet-coupled design of QDS to the field of 2D semiconductors; enabling new advances in the next generation of quantum-confined solid-state materials.

Extension of confined-yet-coupled design to 2D semiconductors

254th National Meeting (2017)

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