Thiophene- and Carbazole-Substituted N-Methyl-Fulleropyrrolidine Acceptors in PffBT4T-2OD Based Solar Cells

authors	Gaspar, H; Figueira, F; Strutynski, K; Melle-Franco, M; Ivanou, D; Tome, JPC; Pereira, CM; Pereira, L; Mendes, A; Viana, JC; Bernardo, G
nationality	International
journal	MATERIALS
author keywords	polymer solar cells; fulleropyrrolidine acceptors; C-70 mono-adducts; regioisomers; stereoisomers
keywords	OPEN-CIRCUIT VOLTAGE; ORGANIC PHOTOVOLTAIC CELLS; FULLERENE DERIVATIVES; ELECTRON-ACCEPTORS; CHARGE SEPARATION; POLYMER; PERFORMANCE; EFFICIENT; PCBM; MORPHOLOGY
abstract	The impact of fullerene side chain functionalization with thiophene and carbazole groups on the device properties of bulk-heterojunction polymer:fullerene solar cells is discussed through a systematic investigation of material blends consisting of the conjugated polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'-di(2-octyldodecyl)-2,2 ' ;5 ' ,2 '' ;5 '' ,2'-quaterthiophen-5,5'-diyl)] (PffBT4T-2OD) as donor and C-60 or C-70 fulleropyrrolidines as acceptors. The photovoltaic performance clearly depended on the molecular structure of the fulleropyrrolidine substituents although no direct correlation with the surface morphology of the photoactive layer, as determined by atomic force microscopy, could be established. Although some fulleropyrrolidines possess favorable lowest unoccupied molecular orbital levels, when compared to the standard PC71BM, they originated OPV cells with inferior efficiencies than PC71BM-based reference cells. Fulleropyrrolidines based on C-60 produced, in general, better devices than those based on C-70, and we attribute this observation to the detrimental effect of the structural and energetic disorder that is present in the regioisomer mixtures of C-70-based fullerenes, but absent in the C-60-based fullerenes. These results provide new additional knowledge on the effect of the fullerene functionalization on the efficiency of organic solar cells.
publisher	MDPI
isbn	1996-1944
year published	2020
volume	13
issue	6
digital object identifier (doi)	10.3390/ma13061267
web of science category	Materials Science, Multidisciplinary
subject category	Materials Science
unique article identifier	WOS:000529208000006