Researchers are focused on novel solar cells designs with power conversion efficiencies that exceed the Shockely-Queisser limit. Hot carrier solar cells (HCSC) and multi-exciton generation (MEG) technology aim to reduce thermalization and band gap losses, which together account for >55% of the total absorbed solar energy.
Hot carrier equilibration and carrier multiplication in both molecular and nano materials are two photophysical mechanisms discussed in this paper for implementation in third generation photovoltaics.
Carrier-carrier scattering must be ensured to achieve high efficiency HCSC, as well as inefficient carrier-phonon scattering. The photon flux parameter is a challenge that still need to be addressed, but graphene and related two-dimensional materials seem to be promising.
Multi-exciton solar cells can offer an actual implementation especially for singlet fission in organic semiconductors, which have shown exceptional quantum efficiency of 200% and lots of potential for new molecule designs.
Interested in better understanding this field? Read more in this Perspective article:
Exceeding the Shockley–Queisser limit in solar energy conversion
Cory A. Nelson, Nicholas R. Monahan and X.-Y. Zhu