InP quantum dots (QDs) have been a major building block of modern display technology due to their high photoluminescence quantum yield (PLQY) in the visible spectrum, superior stability, and eco-friendly composition. However, their applications at short-wave infrared (SWIR) have been hindered by their low efficiency. Here, we report the synthesis of efficient and SWIR-emitting InP QDs by precisely controlling the InP core nucleation using a low-cost ammonia phosphorus precursor, while avoiding size-limiting ZnCl₂ for effective copper doping. Subsequent epitaxial growth of a lattice-matched ZnSe/ZnS multishell enhanced the QD sphericity and surface smoothness and yielded a record PLQY of 66% with an emission peak at 960 nm. When QDs were integrated as the high-refractive-index luminescent core of a liquid waveguide-based luminescent solar concentrator (LSC), the device achieved an optical efficiency of 7.36%. This performance arises from their high PLQY, spectral alignment with the responsivity peak of silicon solar cells, and the optimized core/cladding waveguide structure. These results highlight the potential of InP QDs as a promising nanomaterial for SWIR emission and applications.

Indium phosphide (InP) colloidal quantum dots (QDs) have been drawn significant attention as a potentially less toxic alternative to cadmium-based QDs over the past two decades. The advances in their colloidal synthesis methods have allowed for the synthesis of a wide variety of compositions, heterojunctions, dopants, and ligands that enabled spectral tunability from blue to near-infrared, narrow emission linewidths, and perfect quantum yields approaching unity. Furthermore, it has higher covalency compared to cadmium chalcogenides leading to improved optical stability. The state-of-the-art InP QDs with appealing optical and electronic properties have excelled in many applications such as light-emitting diodes, luminescent solar concentrators (LSCs), and solar cells with high potential for commercialization. This review focuses on the history, recent development, and future aspect of synthesis and application of colloidal InP QDs.

Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum dot levels for LSCs. Here, we demonstrate cascaded energy transfer and exciton recycling at nanoassembly level for LSCs. The graded structure composed of different sized toxic-heavy-metal-free InP/ZnS core/shell QDs incorporated on copper doped InP QDs, facilitating exciton routing toward narrow band gap QDs at a high nonradiative energy transfer efficiency of 66%. At the final stage of non-radiative energy transfer, the photogenerated holes make ultrafast electronic transitions to copper-induced mid-gap states for radiative recombination in the near-infrared. The exciton recycling facilitates a photoluminescence quantum yield increase of 34% and 61% in comparison with semi-graded and ungraded energy profiles, respectively. Thanks to the suppressed reabsorption and enhanced photoluminescence quantum yield, the graded LSC achieved an optical quantum efficiency of 22.2%. Hence, engineering at nanoassembly level combined with nonradiative energy transfer and exciton funneling offer promise for efficient solar energy harvesting.