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Title: Long-Range Order in Nanocrystal Assemblies Determines Charge Transport of Films

Self-assembly of semiconductor nanocrystals (NCs) into two-dimensional patterns or three-dimensional (2- 3D) superstructures has emerged as a promising low-cost route to generate thin-film transistors and solar cells with superior charge transport because of enhanced electronic coupling between the NCs. Here, we show that lead sulfide (PbS) NCs solids featuring either short-range (disordered glassy solids, GSs) or long-range (superlattices, SLs) packing order are obtained solely by controlling deposition conditions of colloidal solution of NCs. In this study, we demonstrate the use of the evaporation-driven self-assembly method results in PbS NC SL structures that are observed over an area of 1 mm × 100 μm, with long-range translational order of up to 100 nm. A number of ordered domains appear to have nucleated simultaneously and grown together over the whole area, imparting a polycrystalline texture to the 3D SL films. By contrast, a conventional, optimized spin-coating deposition method results in PbS NC glassy films with no translational symmetry and much shorter-range packing order in agreement with state-of-the-art reports. Further, we investigate the electronic properties of both SL and GS films, using a field-effect transistor configuration as a test platform. The long-range ordering of the PbS NCs into SLs leads to semiconducting NC-basedmore » solids, the mobility (μ) of which is 3 orders of magnitude higher than that of the disordered GSs. Furthemore, although spin-cast GSs of PbS NCs have weak ambipolar behavior with limited gate tunability, SLs of PbS NCs show a clear p-type behavior with significantly higher conductivities.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [2] ;  [2] ; ORCiD logo [4] ; ORCiD logo [2]
  1. Univ. di Pisa, Pisa (Italy); Univ. of Illinois at Chicago, Chicago, IL (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); NYU Tandon School of Engineering, Brooklyn, NY (United States)
  4. Univ. di Pisa, Pisa (Italy)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
ACS Omega
Additional Journal Information:
Journal Volume: 2; Journal Issue: 7; Journal ID: ISSN 2470-1343
American Chemical Society (ACS)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Molecular Foundry
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; crystal structure; electric transport processes and properties; microstructure; nanocrystals; order; phase; quantum dots; self-assembly; solid state electrochemistry; thin films
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1376694