Recently, the research team of the Institute of Applied Technology and Agricultural Engineering of the Chinese Academy of Sciences’ Hefei Institute of Physical Science has made a series of progresses in small molecule organic hole transport materials. The relevant research results were published in ChemSusChem, ElsevierDyes and Pigments, and the Royal Society of Chemistry. RSC Advances. Small molecular hole transport materials have proven to have very good potential for application in perovskite solar cells. The most widely used hole transport material at present is spiro-OMeTAD, but its synthesis steps are complicated, the cost is high, and the stability in the air is poor. Therefore, the development of new hole transport materials is an indispensable part of the industrialization of perovskite solar cells. In order to develop efficient, stable, and inexpensive small molecule hole transport materials, tetraphenylmethane structures commonly used in organic batteries and OLEDs are introduced to small Molecular hole transport material. Since tetraphenylmethane is a starburst type, there is no intramolecular tension in the helical nucleus, giving it good film formation and high stability. Kong Fantai’s research team designed and developed a tetraphenylmethane core with an aniline group at the periphery. Two small molecules, and synthesized a reference molecule with anisole as a peripheral group. It was found that due to the poor solubility of DPA-TPM and PA-TPM molecules in these three molecules, SEM and AFM showed that the film forming properties of the two were not as good as those of TPA-TPM and spiro-OMeTAD, and the hole mobility was low. Applied to the perovskite device performance is poor. Further study found that tetraphenylmethane as the core of another molecule (TPA-TPM) shows high glass transition temperature, high water contact angle, good film formation and high hole mobility. Perovskite solar cells with TPA-TPM as the hole-transport material are comparable in performance to spiro-OMeTAD, and based on their higher stability than spiro-OMeTAD, they show good potential for application. In addition, the team also introduced two structures, benzodithiophene and pyrrolopyrroledione, which are commonly used in polymer hole transport materials, as linking bridges into small molecule hole transport materials. It was found that the two compounds have poor visible light absorption, the highest occupied molecular orbital (HOMO) energy level is suitable, the solubility is better, and the compound is stable. Its application to perovskite solar cells has shown good performance, although the photoelectric conversion efficiency is lower than that of spiro-OMeTAD, but due to its lower HOMO level, the open circuit voltage of the compound is higher. Due to the introduction of hydrophobic long-chain groups in the compounds, batteries based on them exhibit better stability at high humidity. The experimental results show that these two compounds have good potential for application. In order to further study the effect of the structure of small molecule hole transport materials on the properties of molecules and devices, the team developed three kinds of small molecule hole transport materials with different bridges, and studied its influence on molecules and devices by gradually increasing the conjugacy of molecular bridges. . It was found that with the increase of the degree of condensation of the conjugated bridge, the absorption red shift of the molecule, the HOMO level decreased, the thermal stability increased, and the hole mobility increased significantly. Fluorescence and electrochemical impedance spectroscopy (EIS) studies have found that an increase in the degree of bridging can improve the separation of electron-holes at the interface of the perovskite/hole transport material, thereby improving cell efficiency. Super Bright & Power Saving: 30W handheld LED WORK LIGHT, 1500 Lumen, replace 200W traditional halogen bulb by 30W COB LED and save 80% on electricity bill of lighting Led Work Light,Rechargeable Work Light ,Work Lamp,Rechargeable Led Work Light Ningbo Wason Lighting Technology Co.,Ltd , https://www.wasonlights.com
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