Thickness Effect of Bulk Heterojunction Layers on the Performance and Stability of Polymer:Fullerene Solar Cells with Alkylthiothiophene-Containing Polymer

• Published in: ACS sustainable chemistry & engineering Vol. 5; no. 10; pp. 9263 - 9270
• Main Authors: Nam, Sungho, Song, Myeonghun, Kim, Hwajeong, Bradley, Donal D. C., Kim, Youngkyoo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 02.10.2017
• Subjects: Thickness; Volume stability; Device stability; Bulk heterojunction; Morphology
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.7b02238

We report a pronounced thickness effect of bulk heterojunction (BHJ) layers on the performance and stability of inverted polymer solar cells with the BHJ layers of poly­[(4,8-bis­(5-(octylthio)­thiophen-2-yl)­benzo­[1,2-b:4,5-b′]­dithiophene-co-3-fluorothieno­[3,4- b]­thiophene-2-carboxylate] (PBDT-TS1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The thickness of the BHJ layers was varied from 40 to 120 nm by changing solution concentrations and spin-coating speeds. The results showed that the film thickness considerably affected the performance and stability of devices. The power conversion efficiency reached ca. 9% at the thickness of 80 nm by the optimized nanoscale phase separation between donor and acceptor components. However, the devices with 120 nm-thick BHJ layers showed better device stability under continuous illumination with a simulated solar light due to the well-maintained surface morphology and nanostructure in addition to the improved morphological volume stability.