Research On High-performance Organic Solar Cells Based On Non-halogenated Solvents

At this stage,more and more new high-performance organic photovoltaic materials have been developed and utilized,which has greatly improved the efficiency and stability of organic solar cells(OSCs).However,the current mainstream high-efficiency OSCs are usually prepared using halogenated solvents,which will cause irreparable adverse effects on the ecological environment and human health,which will limit the large-scale production and commercial development of OSCs.Starting from this problem,in this paper,we used non-halogenated aromatic solvents to prepare high-efficiency OSCs based on binary systems.Based on this,the photon absorption,exciton dissociation,charge transport and collection,and morphology characteristics of active layer films were optimized by the thermal substrate process and ternary strategy.The main research contents are as follows:(1)High-efficiency non-halogenated OSCs based on PM6:L8-BO binary system were prepared using o-xylene as solvent using hot substrate processing.Compared with standard sample devices(prepared by cold substrate process),the active layer thin film of the hot substrate device at 60°C exhibits stronger absorption of photons and lower surface rms roughness.In addition,the devices prepared by hot substrate processing showed more optimized exciton dissociation and carrier transport efficiency,so they also showed higher fill factors and short-circuit current densities,and achieved the best efficiency of 17.19%,which was much better than the 15.87% of standard sample devices.Hot substrate devices have a better lifetime performance,maintaining 93.7% of initial efficiency after 60 days in the glove box,better than standard sample devices of 92.3%.The above results show that the thermal substrate processing process can improve the device performance of non-halogenated OSCs,which is a very simple and effective strategy.(2)Furthermore,the ternary strategy was adopted to introduce non-fullerene small molecule receptor BTP-2F2 Cl into the PM6:L8-BO binary system to prepare ternary OSCs with higher efficiency.The absorption peak of BTP-2F2 Cl monomer film prepared by o-xylene was more red-shifted than that of the original material,which indicated that the addition of the third component expanded the absorption spectrum of the blended film to a certain extent.In addition,the three components have higher exciton dissociation efficiency and carrier mobility,so the maximum short-circuit current density is increased from 25.29 m A·cm-2 to 26.37 m A·cm-2,and the maximum efficiency is 17.88%.Through morphological characterization,it is found that the surface of ternary films is smoother than that of binary films,and the donors and acceptors in the film have a better degree of phase separation,which is conducive to the improvement of device performance.Finally,the three components doped with 20% BTP-2F2 Cl showed better thermal stability than the two components by placing different devices on an annealing table at80°C for 150 minutes.In summary,the thermal substrate process and ternary strategy proposed in this paper are effective solutions for the preparation of high-efficiency non-halogenated solvent OSCs.