Thermal modifications of internal quantum efficiencies in the near IR [Si solar cells]

A planar nanostructure inserted in the emitter of a Si solar cell modifies the photovoltaic (PV) conversion performance. In this paper, the authors report a large internal quantum efficiency (IQE) improvement in the near IR (>900 nm) for a series of multi-interface novel device (or MIND) solar cells. The IQE modification can result from increased IR absorption, band-gap narrowing and photogeneration involving thermal phonons and extrinsic energy levels due to post-implantation point defects under stress and might still be improved by an adequate thermal treatment. They show that the near IR modification changes with ambient temperature. This could be related to an evolution of the phonon energy distribution which increases the probability of carrier generation with the participation of phonons.