The Role of Metal Halide Perovskites in Next-Generation Lighting Devices

Abstract

The development of smart illumination sources represents a central challenge for current technology. In this context, the quest for novel materials that enable efficient light generation is essential. Metal halide compounds with perovskite crystalline structure (ABX₃) have gained tremendous interest in the last five years since they come as easy-to-prepare high performance semiconductors. Perovskite absorbers are driving the power-conversion-efficiencies of thin film photovoltaics to unprecedented values. Nowadays, mixed-cation, mixed-halide lead perovskite solar cells reach efficiencies consistently over 20% and promise to get close to 30% in multijunction devices when combined with silicon cells at no surcharge. Nonetheless, perovskites' fame extends further since extensive research on these novel semiconductors has also revealed their brightest side. Soon after their irruption in the photovoltaic scenario, demonstration of efficient color tunable-with high color purity-perovskite emitters has opened new avenues for light generation applications that are timely to discuss herein.

Figure 1

(a) Picture of Milan (Italy) taken from space in 2015 that demonstrates the lighting technology transition from sodium vapor to LED. Reprinted with permission from ref (2). Copyright 2017 American Association for the Advancement of Science. (b) Emission spectrum of different commercial white light sources, i.e., halogen lamp (red curve), fluorescent tube (green curve), and white LED (blue curve). The photopic response of the eye is also shown as a black dashed line. (c) Picture of the photoluminescence exhibited by CsPbX₃ perovskite NCs of different size and composition (X= Cl/Br, Br or Br/I). Adapted from ref (16) with permission from John Wiley & Sons Ltd. (d) Sketch of a perovskite downshifter (left) and a perovskite electroluminescent device (right).

Figure 2

(a) TEM images of CsPbBr₃ NCs. (b,c) Time resolved PL intensity (b) and absorption and PL spectra of CsPbX₃ NCs (c). Reproduced with permission from ref (25). Copyright 2015 American Chemical Society. (d) Color gamut defined by perovskite NCs compared to the NTSC standard. (e) Color temperatures of perovskite-based emitting devices as a function of the ratio of green-to-red perovskite NCs. Adapted from ref (27) with permission from John Wiley & Sons Ltd. (f) Sketch of the mechanism by which complexing with potassium leads to the immobilization of bromide excess (top). PL of K-passivated perovskite films of different composition measured over time. Adapted from ref (30) with permission from Macmillan Publishers Ltd., copyright 2018. (g) Digital picture of MAPbBr₃ NCs embedded in PVDF composite film. (h) Emission spectrum of a white LED that uses as color converter a combination of green emissive MAPbBr₃ /PVDF composite films along with a red emissive phosphor. Adapted from ref (35) with permission from John Wiley & Sons Ltd. (i) Color rendering index, luminous efficiency, and color temperature of a perovskite-based white pcLED as a function of the aging time. Reprinted from ref (36), Copyright (2018), with permission from Elsevier.

Figure 3

(a) PeLED architecture along with a sketch of a perovskite grain decorated with butylammonium (BA) cations. (b) AFM image of a perovskite layer with a 20:100 molar ratio of BABr:MAPbBr₃. (c,d) Current density versus voltage (c) and EQE versus current density (d) of PeLEDs with active layers prepared with different BABr:MAPbBr₃ molar ratios. Adapted from ref (56) with permission from Macmillan Publishers Ltd., copyright 2017. (e) Sketch of a PeLED architecture based on CsPbX₃ NCs. (f) Pictures of the electroluminescence with X = Br/Cl (0.5:0.5), Br, Br/I (0.25:0.75) and I. (g) EQE vs voltage curves. Adapted from ref (69) with permission from John Wiley & Sons Ltd. (g) Dependence of the maximum EQE with its corresponding driving current density of PeLEDs based on CsPbBr₃ NCs. Adapted with permission from ref (72). Copyright 2018 American Chemical Society.