Improved near infrared energy harvesting through heterogeneously coupled SK on SML quantum dot heterostructure

Near Infra Red (NIR) energy harvesting is one of the advanced strategies to improve the overall performance of new generation solar photovoltaics. We introduce here a new heterogeneously coupled Stranski-Krastanov (SK) on Submonolayer (SML) quantum dot (QD) heterostructure, which is capable of enhanced energy conversion efficiency in that typical spectral range. The coupling in the proposed structure has been optimized by varying the growth rate and the barrier thickness between seed SML and top SK QDs. The optimal configuration has been incorporated into a quantum dot solar cell (QDSC). The carrier transitions in this hybrid QD assembly have been investigated through luminescence spectroscopy. An existence of carrier tunnelling between SML and SK QDs has been revealed from the photoluminescence and the photoluminescence excitation spectroscopy. The unique configuration of such coupled QDs shows the presence of resonating energy states. These phenomena ameliorate the absorption efficiency in the NIR regime with increased photoexcited carrier lifetime, which has been reflected in the external quantum efficiency.