Preparation And Properties Of SWCNT/Acridine Derivatives N-type Thermoelectric Composites

Due to shortage of energy,improving the efficiency of energy is of great significance.Thermoelectric materials can achieve direct conversion between thermal energy and electrical energy only through the movement of their internal carriers,which can effectively recover and reuse low-quality waste heat without any additional noise and carbon emissions,so it has considerable application prospects.Among them,organic thermoelectric materials,especially single-walled carbon nanotubes（SWCNTs）and organic small molecule（OSM）composite thermoelectric materials,play an important role in the field of thermoelectricity due to their low cost,low-toxic,flexible and light weight.However,the effect of the structure of OSMs on the composite films is still unclear,and the performance needs to be further improved.In addition,in order to obtain a good performance of thermoelectric devices,both p-type and n-type thermoelectric materials are needed.P-type organic thermoelectric materials have made rapid progress in recent years,and their performance can even be comparable to that of inorganic thermoelectric materials,but there has been a lack of matching organic n-type thermoelectric materials.Thus,research on high-performance organic n-type thermoelectric materials is of great significance.Acridone derivatives have unique three coplanar rings,which have been used in many felds,however,they have seldom been investigated as TE materials.Here,a series of acridine derivatives were designed and synthesized.Then they are composited with SWCNTs to make n-type flexible composite thermoelectric materials.The influence of the skeleton structure and side chain structure on the thermoelectric properties was studied.Finally,the n-type thermoelectric material with the best performance is selected and assembled into devices with the existing p-type thermoelectric materials,and the performances of device are investigated.The details are as follows:1.A series of acridone derivatives containing different terminal amine structures and different numbers of side chains were designed and synthesized,and the relationship between their thermoelectric properties and terminal amine structures was explored.It was found that the highest power factor reached 289.4±2.8μW m^-1 K^-2 at430 K for the composite films of SWCNT/ADTAb,which is one of the highest values for a composite containing n-type small organic molecules and SWCNTs.2.Based on the results above,a series of acridine derivatives with different counterions(Cl^-,SO₄^2-and F^-)and side chains（ADLA1-2 and ADLA4-5）were designed and synthesized.The relationship between their thermoelectric properties and the structures are explored.Among all the composite films,SWCNT/ADLA4 without antagonistic ions exhibite the highest power factor of 195.2μW m^-1 K^-2,at room temperature,which was 4.9 times higher than that of SWCNT/ADTAd(39.8μW m^-1K^-2),indicating that the skeleton and length of the alkyl chains led to significant changes in the thermoelectric properties.In addition,SWCNT/ADLA4 exhibited high power factor values at all temperatures studied,ranging from 154.7μW m^-1 K^-2 to 230.7μW m^-1 K^-2.The results show that adjusting the structure of compounds may be one of the effective methods to promote the development of thermoelectric materials.3.Combined with the relults of the two parts,the SWCNT/ADLA4 composite film with the best thermoelectric performance at room temperature was selected to assemble the thermoelectric device with the p-type SWCNTs,and a TE device composed of five pairs of p-n junction was prepared.At the temperature difference of 74.8 K,the open-circuit voltage reached 41.7 m V and output power was 1.88μW.