Integrating Down-Shifting and Down-Conversion into Metal–Organic Frameworks to Enhance the Spectral Conversion for Solar Cells

Luminescent spectral conversion, including down-conversion (DC) and down-shifting (DS) is a potential route to overcome the spectral mismatch between solar photons and the semiconductor energy gap. Here, we introduce metal organic frameworks (MOFs) that integrate DC and DS processes into one system. Three different MOFs (Gd(BTC)(1), Gd(BPT)(2), and Gd(OBT)(3)) were synthesized doped with lanthanide ions couples. The DS–DC synergistic fluorescent processes were observed in all the MOFs. The overall absorption and near-infrared (NIR) emission intensity are dramatically enhanced (by factors of ∼4 800 and 550) due to the DS-sensitized effect for DC. As for DS process, the DC-bridge effect is quantified for the first time by comparing the NIR quantum yield (QYNIR). Benefiting from the bridge effect, QYNIR (5.30%) of Dy0.01Yb0.10-3 is increased around 3 times greater than the system without DC process, and it is close to the highest value reported for the C–H bond containing Yb3+ emitter. Our study demonstrated that MOFs can be regarded as easily prepared, environmentally friendly and efficient spectral conversion materials to improve the photon-response for c-Si solar cells.