Dependence of the Radiative Efficiency of Quasi-2D Perovskite Light-Emitting Diodes on the Multiquantum-Well Composition

The performance of perovskite light-emitting diode (PeLED) devices based on multiple quantum wells is strongly dependent on the quantum well (QW) distribution in the perovskite films. To fully understand the effect of the QW distribution, a theoretical framework is established to calculate the radiative efficiency based on the distribution of QWs in PeLEDs by combining the charge-carrier recombination and the energy loss in the energy transfer process. A ratio parameter phi is introduced into the dependence of the radiative efficiency on the chargercarrier dynamics for the first time, by taking into account the fact that while the radiative recombination mainly occurs in large-n QWs, the nonradiative recombination exists in both small-n and large-n QWs. The interplays among the energy transfer, the Auger recombination rate, and the radiative recombination rate in determining the dependence of the radiative efficiency on the QW distribution are elucidated. It is revealed that the Auger recombination and the energy loss in energy transfer significantly reduce the radiative efficiency with a large ratio of n = 2 QWs to n >= 5 QWs. As the proportion of n >= 5 QWs increases, the radiative recombination rate becomes lower because of the low charge density in n >= 5 QWs, and the efficiency roll-off becomes milder. The theoretical framework not only successfully predicts and explains the trends of the peak efficiency and the efficiency roll-off of the ITO/PEDOT:PSS/PEA(2) (Cs(0.2)FA(0.8)PbBr(3))(n-1)PbBr4/TPBi/LiF/Al devices, but also sets an upper limit of the efficiency which the actual devices could achieve.