Research On The Performance Of Polymer Solar Cells Based On ADA-type Small Molecule Receptor

In recent years,with the development of small-molecule acceptors（SMAs）,the power conversion efficiency（PCE）of polymer solar cells（PSCs）has exceeded 20%.Representative high-efficiency small molecule configurations include A-D-A and A-DA’D-A,where D and DA’D are polycyclic fused central cores,and A is a terminal electron-withdrawing group.The optoelectronic and photovoltaic properties of SMAs are improved effectively by modifying the side chains on the central cores and end units.Meanwhile,the SMAs added into the binary systems is one of the effective strategy that can optimize the performance of the devices.In this paper,A-D-A type SMAs that the central cores were introduced arylmethylene conjugated side chains were synthesized and prepared binary or ternary PSCs.Furthermore,introducing A-D-AtypeSMAwhoseAunitis2-phenyl-3-（thiophen-2-yl）buta-1,3-diene-1,1,4,4-tetracarbonitrile（PCN）into a highly efficient binary system prepared ternary PSCs.The main research contents and results are as follows:1.To study the influence on the molecular structure,optoelectronic performance and device performance aboute introducing arylmethylene conjugated side chains on the central core and their numbers,we designed and synthesised of A-D-A type small-molecule acceptors DTCFSV-IC and DTCFDV-IC based on fluorenocyclopentadienodithiophene（DTCFV）with different numbers of arylmethylene conjugated side chains.The results show that the two SMAs have better absorption performance and planarity,lower band gap and higher LUMO energy level than DTCFO-IC without conjugated side chains.Respectively,binary PSCs were prepared by mixed SMA and polymer.Compared with DTCFO-IC（PCE=6.92%）and DTCFSV-IC（PCE=6.01%）,the device based on DTCFDV-IC exhibites better photovoltaic performance（PCE=8.89%）with chlorobenzene（CB）as solvent.Using the environmentally friendly non-halogenated solvent o-xylene（o-XY）as the solvent and the fluoropolymer PBDB-TF as the donor,the device based on DTCFDV-IC achieves a equivalent PCE（8.82%）comparable to that of the halogenated solvent.2.In view of the great potential of SMAs containing arylmethylene conjugated side chains in the construction of efficient binary PSCs,four A-D-A type small-molecule receptors IDTV-Si IC,IDTVT-Ph IC,m-IDTV-Ph IC and DTCFDV-IC were introduced into the PBDB-T:PC₇₁BM system as the third component to prepare ternary PSCs.Compared with efficiency of the binary device based on PBDB-T:PC₇₁BM（PCE=8.13%）,the raised PCEs of ternary devices based on IDTV-Si IC,IDTVT-Ph IC,m-IDTV-Ph IC and DTCFDV-IC are 8.93%,9.28%,9.68%and 9.78%,respectively.The reason is the devices of these four ternary PSCs all have high FF.For example,the device with PBDB-T:PC₇₁BM:IDTV-Si IC as the active layer has a significantly higher FF.3.The IDT-T-PCN with the PCN unit as the terminal group was added into the PM6:Y6 system as the third component to prepare high-efficiency ternary PSCs.Compared with the binary device（PCE=15.40%）,based on the PM6:Y6:IDT-T-PCN ternary device has a higher PCE（16.90%）.IDT-T-PCN can properly optimize the morphology of the active layer and improve the FF of ternary device（73.1%→74.7%）.