To Be or not to Be: Band-Like Transport in Quantum Dot Solids

Abstract

Recent experimental data on charge carrier transport in quantum dot solids is analyzed in light of the question whether band-like transport is the most plausible mechanism to account for the observed behavior. Upon reviewing some physical fundamentals of temperature-activated hopping, small polaron hopping and band-like transport, it is established that a combined approach of different experimental methods is required to achieve a satisfactory degree of unambiguousness to address this question. In doing so, at least one example is identified for which a high degree of supporting evidence exists that transport is in fact diffusive. It is highlighted that temperature-dependent Hall Effect measurements play an important role in this respect.

Metal-insulator transition in a semiconductor nanocrystal network

“…S6), suggesting a crossover to the phonon scattering regime expected in metals. However, negative dσ/d T is not exhibited exclusively by metals ( 25 – 27 ), and we emphasize that our key finding is evidence of nonzero σ in the 0 K limit.…”

Quantum Dot Solar Cells: Small Beginnings Have Large Impacts

“…Given all the sources of disorder in a film of QDs (energy disorder caused by different sizes of QDs, different spacing and crystal orientation between QDs, variation in impurities in each QD, variation in ligand coverage, etc.) it is unlikely band-like transport or other long-range transport are the dominant energy transfer mechanisms, unless the QDs are extremely strongly coupled by significant necking or, potentially, by semiconducting inorganic ligands [33,109]. For QD films used in solar cells this strong coupling is usually not the case.…”

Quantifying Angular Correlations between the Atomic Lattice and the Superlattice of Nanocrystals Assembled with Directional Linking

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Typically, the utilized ligands consist of wide-gap, bulky hydrocarbons which render the MCs insulating. [26][27][28][29][30][31][32][33] MCs obtained in this way exhibit average grain sizes of ~150 µm 2 , which enables a detailed characterization by electron and/or X-ray microscopy. 34 Since the optoelectronic properties of PbS NC ensembles bear many opportunities for applications in solar cells or photodetectors, a number of ligand exchange procedures with small organic or inorganic molecules as well as single atom passivation strategies have been developed, all of which greatly increase the carrier mobilities within the SL of NCs.…”