Designing a dual-mode broadband solar spectral converter: The example of Bi3+, Cr3+, Yb3+-tridoped perovskite

Abstract

A promising dual-mode broadband solar spectral converter CaTiO3: Bi3+, Cr3+, Yb3+ was successfully developed by solid-stated reaction. The structure, photoluminescence (PL), photoluminescence excitation (PLE) and diffuse reflectance (DR) spectra in the UV–vis–NIR region have been systematically investigated. The results show that the as-prepared samples simultaneously exhibit two distinct spectral converting patterns, nonlinear quantum-cutting (QC) involving Bi3+–Ti4+ metal-to-metal charge transfer state (BT-MMCTs) → Yb3+: 2F5/2 + Yb3+: 2F5/2 and linear downshift (DS) involving Cr3+: 4T2 → Yb3+: 2F5/2. It deduces that the nonlinear QC is based on a cooperative energy transfer (CET) process while the linear DS belongs to a dipole–dipole mechanism. With the present converter, broadband UV–vis (300–700 nm) photons, which are not fully utilized by the existing c-Si solar cells, can be efficiently harvested and converted into ∼1000 nm NIR photons via the dual-mode mechanism. Moreover, not only the PLE spectrum of CaTiO3: Bi3+, Cr3+, Yb3+ matched well with that of the solar radiation, but also its NIR emission peak position fell well over the spectral response of the commercial crystalline Si (c-Si) solar cells. This as-prepared dual-mode solar spectral converter with multiple advantages can simultaneously realize high quantum yield and broadband conversion, which offers a new and effective way to boost the conversion efficiency of c-Si solar cells. We believe this novel design of dual-mode solar spectral converters can inspire a direction for the synthesis of more advanced UV–vis–NIR phosphors that can be used in Si solar cells.