Open AccessRole of balanced charge carrier transport in low band gap polymer:Fullerene bulk heterojunction solar cells
Author(s) -
Kotlarski Jan D.,
Moet Date J. D.,
Blom Paul W. M.
Publication year - 2011
Publication title -
journal of polymer science part b: polymer physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.65
H-Index - 145
eISSN - 1099-0488
pISSN - 0887-6266
DOI - 10.1002/polb.22243
Subject(s) - band gap , polymer solar cell , solar cell , materials science , active layer , fullerene , organic solar cell , absorption (acoustics) , heterojunction , optoelectronics , charge carrier , polymer , hybrid solar cell , space charge , chemistry , layer (electronics) , nanotechnology , composite material , organic chemistry , physics , thin film transistor , quantum mechanics , electron
Lowering of the optical band gap of conjugated polymers in bulk heterojunction solar cells not only leads to an increased absorption but also to an increase of the optimal active layer thickness due to interference effects at longer wavelengths. The increased carrier densities due to the enhanced absorption and thicker active layers make low band gap solar cells more sensitive to formation of space charges and recombination. By systematically red shifting the optical parameters of poly[2‐methoxy‐5‐(3′,7′‐dimethyloctyloxy)‐ p ‐phenylenevinylene] and 6,6‐phenyl C 61 ‐butyric acid methyl ester, we simulate the effect of a reduced band gap on the solar cell efficiencies. We show that especially the fill factor of low band gap cells is very sensitive to the balance of the charge transport. For a low band gap cell with an active layer thickness of 250 nm, the fill factor of 50% for balanced transport is reduced to less than 40% by an imbalance of only one order of magnitude. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011