Resorcinarene-appended octa-substituted alkyl arms: a new strategy to fabricate supramolecular materials for application in liquid crystals and solar cells

Abstract

A new series of lower-rim-functionalized octa-substituted resorcin[4]arene-based supramolecular compounds with variable alkoxy side chains (–OC₄H₉, –OC₆H₁₃, –OC₈H₁₇, –OC₁₀H₂₁) has been synthesized by a simple two-step procedure. The proposed method is suitable for preparing lower-rim-functionalized resorcinarene-based compounds on a large scale and it is cost-effective as compared to other reported supramesogens. All four functionalized compounds displayed a columnar hexagonal phase (Col_h) over a high mesophase temperature range. The optical texture and thermal behaviour of the target compounds were identified by POM and DSC studies and the molecular organization in the mesogenic state was further confirmed by PXRD. The molecular system based on a resorcinarene core with symmetrical substitution of alkyl arms exhibited columnar type self-assembly organization. All four supramolecules with different side alkyl spacers showed high thermal stability. Compound D₄ with a decyloxy side chain was further optimized to implicate as optical window and transport layer in solar cells to replace the commercially available toxic Cd-based compound. Herein, we developed thin films of compound D₄ on glass and Indium doped Tin oxide glass substartes followed by subjecting the prepared thin films to the characterization tools to explore optical and electical properties. The current–voltage relation shows ohmic-type behaviour. The optical properties display high transmittance in the far visible and NIR regions for all the developed thin films. The derivative showed optical energy band gaps of 1.61 eV, 4.01 eV and 2.27 eV for as deposited and film anneaeld at 100 °C and 200 °C, respectively and findings warrants its suitability for use as an ecofriendly optical window and transport layer in second and third generation solar cells.