Explore the latest research on hot carrier solar cells, a revolutionary technology that could shatter the limits of current solar energy efficiency. Discover how innovative techniques like hot electron tunneling and valley photovoltaics could pave the way for a new era of solar power.
Overcoming the Barrier to Efficiency
Hot carrier solar cells are a promising new type of solar energy technology because they have the potential to allow solar power conversion efficiencies to exceed the Shockley–Queisser limit, which is the theoretical maximal efficiency for single-junction solar cells.
Nevertheless the practical implementation of these concepts has been difficult to realize, especially for efficient extraction across material interfaces with hot electrons. Recent studies have considered utilizing satellite valleys in the conduction band as transit states for hot electrons before harvest.
However, experiments disclose a parasitic barrier at the heterostructure interface between the absorber and extraction layers that makes this transfer problematic. If a topological insulator with perfect gap and no defects is close-contacted to ideal s-wave superconductor, the energy bands of two materials do not match well for normal-electron conductance — resulting in that electrons can pass this barrier by tunneling (a process ruled by nontrivial band structures).
Unlocking the Tunneling Potential
In the new work from the Journal of Photonics for Energy, researchers have explored these evanescent states and their role in electron tunneling with an empirical pseudopotential approach. We use it here to determine energy bands in momentum space, which we align with critical points identified experimentally, and to gain insights into the underlying physics that dictate hot carrier extraction between carrier valley states and through heterointerfaces.
Their results indicated that valley current flows were correlated with an exponentially big tunneling coefficient in indium-aluminum-arsenide (InAlAs) and indium-gallium-arsenide (InGaAs) structures, which have energy bands that do not match up. There is no help either from the extra roughness, cracked network layer a few atoms thick that completely inhibits electron transfer.
Interestingly, the situation becomes much better in a system consisting ofmaterials with AlGaAs barrier and gallium-arsenide (GaAs)well materialswith a composition chosen such that the perturbation created by the aluminumcontent affects a degeneracyonly atthe lower energy satellitevalleys. That system has the advantage of more closely aligning the energy bands and being able to grow atomically. For example, an electron transfer tunneling coefficient between AlGaAs and GaAs may be as high as 0.5 or possibly even 0.88 depending upon the exact stated composition of the AlGaAs.
Conclusion
A recent investigation of hot carrier solar cells has uncovered essential details concerning the intricate tunneling mechanisms that dictate the performance of these high efficiency devices. Different energy band alignment have different effect on hot electron extraction researchers can go further to some sort of the so called limit of efficiency of actual solar technology, thanks to knowledge of this mechanism. The advances of solar being developed could lead to the dawn of a new age for solar power and accessible, renewable energy options.
