Title:	Impact of cell thickness on the induced vertical alignment, dielectric and electrical conductivity of carbon dots doped nematic liquid crystal composite
Authors:	Priscilla, P Fisch, Michael R Kumar, Sandeep Gathania, Arvind Kumar Prakash, Jai Supreet Kumar, Sanjeev Kaushal, Sandeep Castagna, Riccardo Singh, Gautam
Keywords:	Nematic liquid crystal Carbon dots Cell thickness Dielectric properties Electrical conductivity Vertical alignment
Issue Date:	5-Jan-2026
Publisher:	Colloids and Surfaces A: Physicochemical and Engineering Aspects
Citation:	Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2026, Vol. 728(3), AR No. 138735
Abstract:	We report the effect of varying the thickness of cells (d = 5, 7.5, and 15 μm) with planar alignment layers on the induced vertical alignment of a nematic liquid crystal (NLC) composite, 5CB doped with 0.5 wt% carbon dots (CDs). The composite was studied using optical polarizing microscopy, dielectric spectroscopy and electrical conductivity. Optical textures confirm almost defect free induced vertical alignment of the NLC in 5 μm thick cells. At a cell thickness of 7.5 μm, optical defects form but the NLC maintained induced vertical alignment. However, for 15 μm thick samples, larger defects formed leading to a deterioration of optical contrast. The dielectric permittivity decreased with an increase in cell thickness. Also, the short axis molecular relaxation exhibited shift towards higher frequency in 7.5 and 15 μm cells, respectively with respect to the 5 μm cell. This could be attributed to the lowering of the nematic ordering in the composite due to the weakening of the CDs anchoring force on the bulk NLC molecules. The temperature dependent short axis molecular relaxation exhibited Arrhenius behavior and the corresponding activation energy was found to be strongly thickness dependent. Moreover, this study establishes a direct link between cell thickness and electrical conductivity whereby increasing cell thickness: (i) lowers the space charge polarization effect and (ii) decreases the DC conductivity. Our study provides a new insight about the effect of varying cell thickness on the molecular alignment, dielectric, and electrical conductivity of the 0.5 wt% CDs-5CB composites. We anticipate that our findings will be helpful in the development of the next generation display devices with better alignment and reduced space charge polarization effect.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/8641
ISSN:	1873-4359
Alternative Location:	https://doi.org/10.1016/j.colsurfa.2025.138735
Copyright:	2026 Elsevier B.V.
Appears in Collections:	Research Papers (SCM)

Items in RRI Digital Repository are protected by copyright, with all rights reserved, unless otherwise indicated.