Sublimed Materials for OLEDs and Perovskites
Among those factors that affect the performances of organic light-emitting diode (OLED) devices, the purity of OLED materials is one of the most important. This has a direct impact upon not only the performances but also the reliability and stability hence the lifetime of the devices. In fact, the purity of an OLED material has a direct impact upon the charge (electron and hole) transport capacity, so it is a key aspect to examine for satisfying performance of an organic electronic device.
Wöhrle et al. investigated the material purity impacts on photovoltaic performance . They showed that the non-sublimated materials gave rougher surface on the thin film. Therefore, pinholes emerged and formed the short circuits that deteriorated the device performance. Salzman also proved that the PCE of copper phthalocyanine (CuPc)-based OPV devices can be enhanced over five times when the donor material was efficiently purified . It was further pointed out that the less purified thin film exhibited low carrier mobility, leading to a small fill factor (FF).
Liu has also demonstrated that The power conversion efficiency was improved from 2.7% to 4.3% by the sublimation of SubPc. Atomic force microscopic images showed that the crystallinity was improved with sublimed SubPc, leading to the significantly enhanced hole mobility of SubPc in orders of magnitude as estimated by the space-charge limited current .
Sublimation is a technique used to obtain ultra pure grade chemicals to get rid of mainly trace metals, inorganic and volatile impurities. Sublimation happens under certain pressure for chemicals to only go through two physical stages from a solid sate to vapour (gas) and then the vapour condensed to a solid state on a cool surface (referred to as cold finger deposition). The most typical examples of sublimation are iodine and dry ice. Sometime multiple sublimation is needed for even higher purities.
With our collection of sublimed materials of great purity, you can have confidence in your experiment results and a jump boost for your research, relating to the lifetime and the stability of the device you build up and most importantly, the purity of the colour display and overall your device performance.
Interesting fact: Sublimation happens to the snow on the top face of Mt. Everest due to low temperatures, strong winds, intense sunlight and very low air pressure, a recipe for sublimation to occur.
- Investigations of n/p-junction photovoltaic cells of perylenetetracarboxylic acid diimides and phthalocyanines, D. Wöhrle et al., J. Mater. Chem., 5, 1819-1829 (1995), DOI: 10.1039/JM9950501819.
- The effects of copper phthalocyanine purity on organic solar cell performance, R. F. Salzman et al., Org. Electronics, 6, 242-246 (2005), doi:10.1016/j.orgel.2005.09.001.
Efficient Organic Photovoltaic Device Using a Sublimated Subphthalocyanine as an Electron Donor, S. Liu et al., ECS Solid State Lett., 1 (5), 70-72 (2012), doi: 10.1149/2.002205ssl.