Molecular Intercalation and Cohesion of Organic Bulk Heterojunction Photovoltaic Devices. (17th January 2013)

• Record Type: Journal Article
• Authors: Bruner, Christopher; Miller, Nichole C.; McGehee, Michael D.; Dauskardt, Reinhold H.
• Is Part Of: Advanced functional materials. Volume 23:Number 22(2013)
• Page Start: 2863
• Page End: 2871
• Publication Date: 2013-01-17
• Subjects: fullerenes -- photovoltaic devices -- solar cells -- thin films -- fracture; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201202969
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract: The phase separated bulk heterojunction (BHJ) layer in BHJ polymer:fullerene organic photovoltaic devices (OPV) are mechanically weak with low values of cohesion. Improved cohesion is important for OPV device thermomechanical reliability. BHJ devices are investigated and how fullerene intercalation within the active layer affects cohesive properties in the BHJ is shown. The intercalation of fullerenes between the side chains of the polymers poly(3, 3″′‐didocecyl quaterthiophene) (PQT‐12) and poly(2, 5‐bis(3‐hexadecylthiophen‐2‐yl)thieno[3, 2‐b]thiophene (pBTTT) is shown to enhance BHJ layer cohesion. Cohesion values range from ≈1 to 5 J m −2, depending on the polymer:fullerene blend, processing conditions, and composition. Devices with non‐intercalated BHJ layers are found to have significantly reduced values of cohesion. The resulting device power conversion efficiencies (PCE) are also investigated and correlated with the device cohesion. Abstract : The effects of molecular intercalation and thermal annealing are described on active layer cohesion in organic photovoltaics with the donor polymer poly(3, 3″′‐didocecyl quaterthiophene) (PQT‐12). Increased cohesion is related to the extent of intercalation and the presence of fracture resistant domains. Correlation with annealing and device efficiency is presented.