Improving the performance of all-inorganic perovskite light-emitting diodes through using polymeric interlayers with a pendant design

Despite demonstrating higher photoluminescence quantum yield and better ambient and operational stability than organic-inorganic hybrid perovskites, all-inorganic perovskites encounter the problem of inferior film quality and interfacial electrical properties, which limits the resultant device performance. In this study, three polymers, P4a-c, bearing distinct pendant groups based on a similar conjugated group are synthesized and employed as an interlayer to modify the PEDOT:PSS/CsPbBr3 interface. Due to the pendant design, P4a-c possess deep-lying HOMO levels and high transparency across the visible range. The different structures of the pendant groups in P4a-c are shown to result in their different propensity in energy-level modulation and solid-state aggregation, which plays a non-trivial role in affecting the resulting device performance. Due to the more appropriate energy levels and better regulation of CsPbBr3 crystals, P4c with a polar bridge moiety is shown to better mediate the performance of the derived device. The P4c-mediated PeLED delivers six times enhanced luminance (Lmax, ∼36 000 cd m-2) and 3.6 times enhanced external quantum efficiency (EQE, 2.16%) as compared to the control device (∼6000 cd m-2, 0.60%). Notably, all the devices using P4a-c interlayers deliver a lower turn-on voltage than the control device, clearly revealing the positive role of P4a-c interlayers on diminishing the barrier across the associated interface to improve charge injection efficiency.