Efficient photon upconversion at low light intensities promises major advances in technologies spanning solar energy harvesting to deep-tissue biophotonics. Here, we discover the critical mechanisms that enable near-infrared dye antennas to significantly enhance performance in lanthanide-doped upconverting nanoparticle (UCNP) systems, and leverage these findings to design dye–UCNP hybrids with a 33,000-fold increase in brightness and a 100-fold increase in efficiency over bare UCNPs. We show that increasing the lanthanide content in the UCNPs shifts the primary energy donor from the dye singlet to its triplet, and the resultant triplet states then mediate energy transfer into the nanocrystals. Time-gated phosphorescence, density functional theory, singlet lifetimes and triplet-quenching experiments support these findings. This interplay between the excited-state populations in organic antennas and the composition of UCNPs presents new design rules that overcome the limitations of previous upconverting materials, enabling performances now relevant for photovoltaics, biophotonics and infrared detection.

在低光强度下高效的光子上转换有望在从太阳能收集到深层组织生物光子学的技术上取得重大进展。在这里，我们发现了使近红外染料天线能够显着增强镧系元素掺杂的上转换纳米粒子（UCNP）系统性能的关键机制，并利用这些发现设计出染料-UCNP杂种，其亮度增加了33,000倍，而杂色则增加了100倍。效率是裸UCNP的两倍。我们表明，增加UCNPs中的镧系元素含量会将主要的能量供体从染料单重态转变为其三重态，然后所得的三重态将介导的能量转移到纳米晶体中。时间门控磷光，密度泛函理论，单重态寿命和三重态猝灭实验支持了这些发现。