In-Situ Growth of CdS Nanorods in PTB7 by Solvothermal Process for Hybrid Organic Inorganic Solar Cell applications

Abstract

We demonstrate a high yielding, green approach using solvothermal, in situ growth of CdS nanorods (NRs) in a low band gap polymer, poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7). The use of chloroaniline dithiocarbamate and chloroaniline as ligands to functionalize the Cd (II) ions provides a new path for solubilization of Cd (II) complex in the chlorobenzene solvent. It removes use of volatile and hazardous chemicals such as pyridine as ligand which are conventionally used to enhance solubility of such complexes. It is the first example of solvothermal process used for in situ growth of CdS NRs in a polymer matrix. This nanocomposite is used to fabricate hybrid-organic–inorganic-solar cells (HOISC) as donor–acceptor combination in the bulk hetrojunction (BHJ) geometry. The incorporation of CdS NRs shows significant decrease in the band gap of PTB7 from 1.71 eV to 1.59 eV and the photoluminescence (PL) studies show significant quenching in the PL of PTB7 by the addition of CdS NRs. This suggests that the PTB7:CdS NRs is a potential nanocomposite for the bulk heterojunction active layer in the HOISCs. The HOISCs fabricated using the PTB7:CdS as donor–acceptor combination give power conversion efficiency of the order of 1.16 %. This work has implication in the development of green economical and efficient HOISC by using highly controlled synthetic process.