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Enhanced Thermal Stability and Efficiency of Polymer Bulk‐Heterojunction Solar Cells by Low‐Temperature Drying of the Active Layer
Author(s) -
Lin Ching,
Lin EnYung,
Tsai FengYu
Publication year - 2010
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200901807
Subject(s) - materials science , polymer solar cell , annealing (glass) , energy conversion efficiency , chemical engineering , active layer , crystallite , thermal stability , nucleation , polymer , heterojunction , optoelectronics , layer (electronics) , nanotechnology , composite material , organic chemistry , chemistry , metallurgy , thin film transistor , engineering
This study addresses two key issues, stability and efficiency, of polymer solar cells based on blended poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) by demonstrating a film‐forming process that involves low‐temperature drying (−5 °C) and subsequent annealing of the active layer. The low‐temperature process achieves 4.70% power conversion efficiency (PCE) and ∼1250 h storage half‐life at 65 °C, which are significant improvements over the 3.39% PCE and ∼143 h half‐life of the regular room‐temperature process. The improvements are attributed to the enhanced nucleation of P3HT crystallites as well as the minimized separation of the P3HT and PCBM phases at the low drying temperature, which upon post‐drying annealing results in a morphology consisting of small PCBM‐rich domains interspersed within a densely interconnected P3HT crystal network. This morphology provides ample bulk‐heterojunction area for charge generation while allowing for facile charge transport; moreover, the P3HT crystal network serves as an immobile frame at heating temperatures less than the melting point ( T m ) of P3HT, thus preventing PCBM/P3HT phase separation and the corresponding device degradation.