Solution-based colloidal synthesis of hybrid P3HT: Ternary CuInSe2 nanocomposites using a novel combination of capping agents for low-cost photovoltaics

• Wet-route synthesis of hybrid P3HT:CISe nanocomposites reported.
• Novel combination of capping agents: volatile aniline and non-volatile 1-Octadecene.
• Aniline–octadecene equilibrium phase diagram tunes polydispersity of CISe nanocrystals.
• Beneficial effects of aniline–octadecene capping realized for hybrid nanocomposites.
• Hybrid P3HT:CISe(AO) nanocomposites-potential application for low-cost photovoltaics.

In this work, ternary CuInSe2 (CISe) chalcopyrite nanocrystallites efficiently passivated by a novel combination of capping agents viz: aniline and 1-octadecene during chemical route synthesis were dispersed in conducting polymer matrix poly(3-hexylthiophene) (P3HT). By varying the composition and concentration of the ligands, the properties of the resulting CISe nanocrystallites and its corresponding polymer nanocomposites thus could be tailored. The structural, morphological and optical studies accomplished by various complimentary techniques viz. Transmission Electron Microscopy (TEM), Contact angle, Photoluminescence (PL) and Raman have enabled us to compare the different hybrid organic (polymer)-inorganic nanocomposites. On the basis of aniline–octadecene equilibrium phase diagram, the polydispersity of the CISe nanocrystals could be tuned by using controlled variations in the reaction conditions of nucleation and growth such as composition of the solvent and temperature. To the best of author’s knowledge, the beneficial effects of both the capping agents; aniline and octadecene contributing well in tandem in the development of large-sized (100–125 nm) high quality, sterically- and photo-oxidative stable polycrystalline CISe and its corresponding polymer (P3HT):CISe composites with enhanced charge transfer efficiency has been reported for the first time. The low-cost synthesis and ease of preparation renders this method of great potential for its possible application in low-cost hybrid organic–inorganic photovoltaics.

In this work, we have demonstrated the beneficial effect of surface passivation of CISe nanocrystals using a novel combination of capping agents viz. an arylamine aniline and non-coordinating solvent 1-octadecene mixture on the structural and optoelectronic properties of its corresponding polymer (P3HT):CISe nanocomposites. Here, on the basis of capping agent's equilibrium phase diagram, the synthesis and growth conditions were maneuvered to promote the formation of large-sized, high quality and stable CISe nanocrystals. The high quality rendered by AO-capped CISe nanocrystallites is also imparted to its respective polymer (P3HT):CISe composite as inferred from its high photo-stability against laser-exposure and dominance of charge transfer as compared to its corresponding individually A/O-capped CISe polymer composites respectively. This straightforward and cost-effective approach could pave way for its potential application in an effective charge separation in hybrid photovoltaics.The figure shows the Temperature vs Mole fraction graph of two different phases (aniline and 1-octadecene) in equilibrium.Figure optionsDownload as PowerPoint slide