Highly Efficient Infrared Quantum Cutting in Tb³⁺−Yb³⁺ Codoped Silicon Oxynitride for Solar Cell Applications

A high efficiency infrared quantum cutting effect in a Tb³⁺–Yb³⁺ codoped silicon oxynitride system is demonstrated. The thin films are deposited on Si substrates by reactive magnetron co‐sputtering of a Si target topped with Tb₄O₇ and Yb₂O₃ chips under pure nitrogen plasma. The photoluminescence dynamics are investigated, revealing a quantum efficiency of this system at 980 nm up to 197% for the higher Yb³⁺ concentration. Thus, via a cooperative transfer mechanism between Tb³⁺ and Yb³⁺, an absorbed UV–visible photon gives rise to almost two emitted IR photons. Such a down‐conversion effect is demonstrated upon indirect excitation of energy donors, via defect states in the host matrix. These down‐converter films could be directly and easily integrated on top of the Si‐based solar cell to improve the photoelectric conversion efficiency at a lower cost. An evaluation of the additional external quantum efficiency is deduced from this optical system and found to be almost 2%.