The electronic interaction between vertically coupled Stranski-Krastanov and submonolayer quantum dots: a detailed investigation of carrier transitions and correlation with improved NIR energy conversion efficiency

Quantum dot solar cell (QDSC) has been introduced to stretch the quantum efficiency towards longer wavelength. This is an efficient way to harvest photons with sub band gap energy values. Still, these can absorb photons within a particular energy band, depending upon the size distribution and corresponding energy levels of such quantum dots. To increase the energy conversion efficiency in this near infrared region one can introduce electronic coupling or varying size distribution of quantum dots. In epitaxially grown III-As based solar cell has shown very promising results with In(Ga)As/GaAs quantum dots, embedded periodically in the active region. In the current study, we are showing a new hybrid way to use both Stranski-Krastanov (SK) and submonolayer (SML) quantum dots simultaneously for better near infrared energy harvesting. With a detailed investigation on photo-generated carrier dynamics, and correlating this with photovoltaic energy conversion efficiency, we have established this hybrid SK-SML QDSC as a superior configuration than its homogeneous counterpart (SK QDSC).