Halide perovskite light-emitting devices possess remarkable characteristics such as high efficiency, superior color purity, and an extensive color range. However, their integration into industrial applications is often hindered by the complex multilayer structure of the devices, as well as the stability issues caused by heating during operation.
A promising solution to these challenges comes in the form of halide perovskite light-emitting electrochemical cells. These innovative optoelectronic devices differ from traditional perovskite light-emitting diodes in their simple monolayered architecture. The perovskite light-emitting electrochemical cell comprises a silicon substrate, a multifunctional single composite perovskite layer (consisting of a mixture of halide perovskite microcrystals, a polymer support matrix, and added mobile ions), and a transparent top contact made of single-walled carbon nanotube film.
The use of silicon as a substrate offers the advantage of excellent thermal conductivity, resulting in 40% lower thermal heating during device operation compared to the conventional ITO/glass substrate. Moreover, when a positive bias is applied to the device, it can achieve a luminance exceeding 7,000 cd/m2 at a wavelength of 523 nm, corresponding to the green color. Conversely, when a negative bias is applied, the device functions as a photodetector with a remarkable sensitivity of up to 0.75 A/W for wavelengths in the blue or UV regions. It exhibits a specific detectivity of 8.56∙1011 Jones and a linear dynamic range of 48 dB. These impressive performance metrics are indicative of the technological potential of such a device. Additionally, the researchers have successfully demonstrated a 24-pixel indicator display and achieved device miniaturization by creating electroluminescent images with features smaller than 50 μm.
Perovskite light-emitting electrochemical cells offer a viable alternative to conventional perovskite light-emitting diodes. Not only do they feature a much simpler architecture and design, with a single functional layer replacing multiple active layers involved in charge separation and transport, but they also possess the extraordinary properties of LEDs, including high efficiency, exceptional color purity, and a broad color gamut.
The mechanism behind the remarkable performance of perovskite light-emitting electrochemical cells differs significantly from that of LEDs. When an electrical bias is applied to the device, positive and negative ions within the perovskite layer migrate dynamically toward their corresponding electrodes, creating a p-i-n structure inside the perovskite layer. This dynamic migration allows for efficient recombination of electrons and holes, resulting in photon emission. By exploring alternative approaches to traditional LED technology, we can expand the range of industrial possibilities and open new avenues for research and development.
The device under investigation exhibits extraordinary capabilities in both light emission and light detection, showcasing its dual-functionality. Moreover, it demonstrates improved resilience to heating during operation, thanks to the incorporation of a silicon substrate in the design of perovskite light-emitting electrochemical cells. Silicon is a fundamental component of CMOS (complementary metal–oxide–semiconductor) technology, which forms the basis for manufacturing various semiconductor chips and displays. By combining emerging materials like perovskite with silicon, the research community takes a significant stride towards achieving commercially viable perovskite light-emitting electrochemical cells.
Another significant advantage of the device design is the use of an ITO-free transparent electrode, which relies on single-walled carbon nanotubes. Typically, ITO (Indium-Tin Oxide) is a commonly employed transparent conductive material in perovskite photovoltaics and optoelectronics. However, indium, one of its constituents, is a limited resource. By finding alternatives to ITO based on abundant elements, the industry can overcome the challenges posed by indium scarcity.
The findings of this research have been published in the esteemed journal Opto-Electronic Advances.