Researchers from City University of Hong Kong developed small-grained inorganic perovskite films with improved photoluminescence quantum yield
A team of researchers from City University of Hong Kong (CityU) developed a new and efficient fabrication approach to produce all-inorganic perovskite films with efficient optical properties and stability. The breakthrough enables the development of high color-purity and low-cost perovskite LEDs with a high operational durability. The efficient fabrication approach creates smooth inorganic perovskite films with enhanced performance and stability. The team found that cesium trifluoroacetate (TFA) can be used as the cesium source in the one-step solution coating as opposed to the commonly used cesium bromide (CsBr).
This helps to achieve fast crystallization of small-grained CsPbBr3 perovskite crystals that form the smooth and pinhole-free perovskite films. This can be majorly attributed to the interaction of TFA- anions with lead (Pb2+) cations in the CsPbX3 precursor solution, which improves the crystallization rate of perovskite films and suppresses surface defects. Therefore, the team developed efficient and stable green PeLEDs based on these films and the maximum current efficiency was 32.0 cd A-1, accounting for an external quantum efficiency of 10.5%, which is considered as satisfactory in current PeLEDs.
Moreover, the team found that the all-inorganic perovskite LEDs based on these films demonstrated a record operational lifetime. The recorded half-lifetime was over 250 hours at an initial luminance of 100 cd m-2, accounting to a 17-fold improvement in operational lifetime as compared with CsBr-derived PeLED. According to Andrey Rogach, Chair Professor of Photonics Materials at CityU, the research suggests that the high color-purity and low-cost all-inorganic lead halide perovskite films can be used to create highly efficient and stable LEDs through a simple optimization of the grain boundaries. These films are easy to fabricate and can be easily deposited by printing and can find potential application in various optoelectronic devices. The research was published in the journal Nature Communications on February 8, 2019.