Broadband White‐Light‐Emitting Electrochemical Cells

Emerging organic light‐emitting devices, such as light‐emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal‐free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal‐free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric‐field‐driven structural transformation of the original green‐light emitter structure into a red‐emitting structure. Utilizing the electric field‐driven structural transformation of green‐light emitting bis‐(benzyltriphenylphosphonium)tetrabromidomanganate(II), ([Ph3PBn]2[MnBr4]), to a red emitter, allows to realize a broad white‐light‐emitting electrochemical cell (LEC) which is not based on a critical or noble metal with a high color rendering index.