Substitutional Doping of Yb3+in CsPbBrxCl3-x Nanocrystals

Lead halide perovskite nanocrystals (NCs) have been widely studied in recent years because of their huge application potential as a cost-effective UV-vis semiconductor. On the other hand, introduction of rare-earth (RE) ions is a popular way to modify the photonic properties of semiconductors because of their sharp electronic transitions in vis-NIR. However, with small absorption cross sections, for practical applications of RE-doped materials, there is an urgent need for efficient sensitization. Perovskites are natural candidates to host RE dopants, providing strong absorption and high tolerance to defects. Here, we prepare and explore the excitation mechanism of Yb3+-doped CsPbBrxCl3-x perovskite NCs. The produced materials apparently have low doping concentrations as evidenced by the analysis, but nevertheless, we observe emission which originated from excitation through the perovskites. Using postsynthesis modification of the perovskite composition, together with PL characterization, allows the study of optically active Yb3+ ions. We study the role of band gap energy on Yb3+ excitation and moreover provide evidence that even at low doping concentrations, optically active Yb3+ dopants are found within the perovskite lattice in substitutional positions of the lead ions.