Suppressed spectral blue-shift in ZnS-coated CuInS₂ quantum dots for efficient luminescent solar concentrators

It is well established that ZnS shell coating on CuInS₂ quantum dots (QDs) can significantly enhance their photoluminescence quantum yield (PLQY); however, it can also induce substantial spectral blue-shift and increase spectral overlap between absorption and emission, which is detrimental to the performance of luminescent solar concentrators (LSCs). In this work, we developed an optimized ZnS shell coating strategy by carefully balancing precursor reactivities, which yielded CIS/ZnS QDs with a significantly suppressed PL blue-shift (16 nm) and a high PLQY of 75%. After being embedded in an off-stoichiometric thiol-ene (OSTE) matrix, the spectral overlap integral (OI) value of the QDs further reduced to 0.086, which was the smallest OI value reported for CIS/ZnS QDs and their analogues. Owing to the small reabsorption loss from the QDs, the fabricated LSC with dimensions of 9 × 9 cm² demonstrated an external optical efficiency of 9.69% and a power conversion efficiency of 2.23%, with an average visible transmittance of 45%. We believe that our ZnS shell coating strategy could significantly benefit CIS/ZnS QD-based LSCs, especially in large-area devices targeted for practical building-integrated photovoltaic applications.