Blue‐Emitting Boron‐ and Nitrogen‐Doped Carbon Dots for White Light‐Emitting Electrochemical Cells

Abstract This work describes the first use of blue‐emitting boron‐ and nitrogen‐doped carbon dots (BN‐CDs), rationalizing their photoluminescence behavior in solution and ion‐based thin‐films to prepare white light‐emitting electrochemical cells (LECs). In detail, a cost‐effective and scalable water‐based microwave‐assisted synthesis procedure is set for BN‐CDs featuring an amorphous carbon‐core doped with N and B. While they show a bright (photoluminescence quantum yield of 42%) and excitation‐independent blue‐emission (440 nm) in solution related to emitting n−π^* surface states, they are not emissive in thin‐films due to aggregation‐induced quenching. Upon fine‐tuning the film composition (ion‐based host), an excitation dependent emission covering the whole visible range is noted caused by interaction of the ion electrolyte with the peripheral functionalization of the BN‐CDs. Moreover, the efficient energy transfer from the host to the BN‐CDs emitting species enabled good performing LECs with white emission (x/y CIE coordinates of 0.30/0.35, correlated color temperature of 6795 K, color rendering index of 87) and maximum luminance of 40 cd m⁻², and stabilities of a few hours. This represents a significant improvement compared to the prior‐art monochromatic CD‐based LECs with similar brightness levels, but stabilities of <1 min.