TY - JOUR
T1 - High open-circuit voltage photovoltaic cells with a low bandgap copolymer of isothianaphthene, thiophene, and benzothiadiazole units
AU - Kim, Jung Yong
AU - Qin, Yang
AU - Stevens, Derek M.
AU - Kalihari, Vivek
AU - Hillmyer, Marc A.
AU - Frisbie, C. Daniel
PY - 2009
Y1 - 2009
N2 - A novel conjugated copolymer (PITN-co-ThBTD) composed of alternating isothianaphthene, thiophene, and benzothiadiazole units was synthesized and characterized. The polymer has a low bandgap of 1.55 eV as a result of the intrachain coupling between electron-donating/withdrawing units. Thermal analysis and wide-angle X-ray scattering (WAXS) reveal that the polymer has a largely amorphous structure. Blends of PITN-co-ThBTD with the electron acceptor methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were studied as a function of increasing PCBM content by WAXS, atomic force microscopy, charge transport, and photovoltaic measurements. The PCBM solubility limit, i.e., the phase-separation point, was estimated to be 30 wt % PCBM, beyond which charge carrier transport switches from hole only to ambipolar (both electron and hole) in a field-effect transistor testbed. Bulk heterojunction solar cells were constructed from PITN-co-ThBTD films blended with varying weight fractions of PCBM. The best performance was observed at high PCBM compositions (∼70-80% PCBM) rather than at the phase separation point. The power conversion efficiency of 0.9% with short circuit current, Jsc = 3.4 mA/cm2, open circuit voltage, Voc = 0.83 V, and fill factor, FF = 32%, was measured under AM 1.5, 100 mW/cm2 illumination. The high Voc is a promising result for low bandgap polymer-based photovoltaics, while the low FF is a performance-limiting factor originating from the disordered structure of the polymer and the thickness of the film (100 nm).
AB - A novel conjugated copolymer (PITN-co-ThBTD) composed of alternating isothianaphthene, thiophene, and benzothiadiazole units was synthesized and characterized. The polymer has a low bandgap of 1.55 eV as a result of the intrachain coupling between electron-donating/withdrawing units. Thermal analysis and wide-angle X-ray scattering (WAXS) reveal that the polymer has a largely amorphous structure. Blends of PITN-co-ThBTD with the electron acceptor methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were studied as a function of increasing PCBM content by WAXS, atomic force microscopy, charge transport, and photovoltaic measurements. The PCBM solubility limit, i.e., the phase-separation point, was estimated to be 30 wt % PCBM, beyond which charge carrier transport switches from hole only to ambipolar (both electron and hole) in a field-effect transistor testbed. Bulk heterojunction solar cells were constructed from PITN-co-ThBTD films blended with varying weight fractions of PCBM. The best performance was observed at high PCBM compositions (∼70-80% PCBM) rather than at the phase separation point. The power conversion efficiency of 0.9% with short circuit current, Jsc = 3.4 mA/cm2, open circuit voltage, Voc = 0.83 V, and fill factor, FF = 32%, was measured under AM 1.5, 100 mW/cm2 illumination. The high Voc is a promising result for low bandgap polymer-based photovoltaics, while the low FF is a performance-limiting factor originating from the disordered structure of the polymer and the thickness of the film (100 nm).
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U2 - 10.1021/jp9079926
DO - 10.1021/jp9079926
M3 - Article
AN - SCOPUS:73849096509
SN - 1932-7447
VL - 113
SP - 21928
EP - 21936
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 52
ER -