Periodically-Ordered One and Two Dimensional CdTe QD Superstructures: A Path Forward in Photovoltaics
By using the state-of-the-art theoretical method, we herein explore the potentiality of covalently linked periodically-ordered 1D chain, 2D hexagonal and square ordered superstructures of CdTe QDs in photovoltaics. One of the major factors that controls the photovoltaic efficiency is the electron-hole recombination which in turn depends on the spatial separation of these charge carriers. Our theoretical findings show that the HOMO and LUMO states of CdTe QD assembly are well separated and this separation increases with increasing the number of QDs in assembly. This results indicate large spatial separation of photoexcited electron and hole pairs which prolongs the carrier lifetime and thus slows down the chance of electron-hole recombination. Next, we attached fullerene moiety to the CdTe QD assembly. The photoexcited electrons of QD assembly potentially transfer to low energy lying conduction band of fullerene and the spatial charge separation increases with increasing the number of QDs in assembly, promising a novel feature for reducing the electron-hole recombination drastically by increasing the number of QDs in assembled QD-fullerene composite. The assembled QD-fullerene composites exhibit very high photoconversion efficiency of 19.3%, opening up new possibilities for designing efficient solar energy harvesting devices based on assembled QD.