To ascertain the precise energy levels of the organic-inorganic hybrid 2D perovskites, we employed ultraviolet photoelectron spectroscopy (UPS) and low-energy inverse photoelectron spectroscopy (LEIPS) to probe the ionization potential (IP) and electron affinity (EA), respectively. LEIPS is particularly advantageous for its minimal chemical degradation impact on organic constituents, rendering it an optimal technique for assessing the unoccupied conduction band of organic semiconductors. As depicted in Figure , the IP was determined to be 6.8 eV using UPS. Concurrently, LEIPS facilitated the measurement of UV light emission from our sample upon exposure to low-energy electrons, enabling the calculation of an EA of 3.7 eV. Comprehensive details and calculations are presented in the supplementary materials (see Figures and). Consequently, the bandgap of the perovskite was calculated to be 3.1 eV, corroborating the emission and absorption data presented in Figure . Traditional deep blue and violet PeLEDs often employ 2,2′,2"-(1,3,5-benzinetriyl)-tris(1-phenyl-1H-benzimidazole) (TPBi) as the electron transport layer (ETL) due to its favorable electronic properties. However, as delineated by the energy level diagram in Figure , TPBi's highest occupied molecular orbital (HOMO) is positioned at a higher energy compared to the valence band maximum of PEA2PbCl1Br3. This mismatch hinders effective hole confinement within the perovskite layer, potentially facilitating hole leakage and non-radiative recombination processes. Moreover, the bandgap of TPBi, approximately 3.5 eV, is very close to the perovskite bandgap of 3.1 eV, raising concerns over emission spectral purity. The violet curve in Figure illustrates the electroluminescence (EL) spectrum of a PEA2PbCl1Br3 device with a traditional TPBi structure. When contrasted with the EL spectrum from a TPBi-only (no perovskite) device (Figure ), notable emission from the TPBi layer is observed, indicating excitonic recombination within TPBi that detracts from the desired device performance.