2 research outputs found
Revealing Hidden UV Instabilities in Organic Solar Cells by Correlating Device and Material Stability
With stateâofâtheâart organic solar cells (OSCs) surpassing 16% efficiency, stability becomes critical for commercialization. In this work, the power of using photoluminescence (PL) measurements on plain films is demonstrated, as well as highâperformance liquid chromatography analysis to reveal the origin of UV instabilities in OSCs based on the most commonly used acceptors PC70BM ([6,6]âphenylâC71âbutyric acid methyl ester), ITIC (3,9âbis(2âmethyleneâ(3â(1,1âdicyanomethylene)âindanone))â5,5,11,11âtetrakis(4âhexylphenyl)âdithieno[2,3âd:2â˛,3â˛âdâ˛]âsâindaceno[1,2âb:5,6âbâ˛]dithiophene), and oâIDTBR (indacenodithiopheneâbased nonâfullerene acceptor). The UV dependent stability tests reveal instabilities in solar cells based on PC70BM and ITIC while devices based on oâIDTBR are highly stable even under UV illumination. The analysis of solar cell devices based on charge extraction and subâbandgap external quantum efficiency only shows the UVâdependent emergence of traps, while PL spectra of plain films on glass allows the disentanglement and identification of individual instabilities in multiâcomponent bulkâheterojunction devices. In particular, the PL analysis demonstrates UV instabilities of PC70BM and ITIC toward the processing additive 1,8 diiodooctane (DIO). The chemical analysis reveals the inâdepth mechanism, by providing direct proof of photochemical reactions of PC70BM and ITIC with UVâinduced radicals of DIO. Based on this scientific understanding, it is shown how to stabilize PBQâQF:PC70BM devices