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Title:
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Exploring the limits of hybrid TiO2/conjugated polymer photovoltaic cells
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-11-2005
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ECN report number:
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Document type:
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ECN-RX--05-030
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Conference Paper
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Number of pages:
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Full text:
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8
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Download PDF
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Presented at: SPIE Conference; Optics & Phonotonics, San Diego, USA, 31 juli 2005-4 augustus 2005.
Abstract:
In hybrid polymer photovoltaics, conjugated polymers are combined with
wide bandgap metal oxide semiconductors like TiO
2 or ZnO.
Reported maximum power conversion efficiencies (PCE) at AM1.5G conditions
for a hybrid polymer bulkheterojunction device are up to 1.6 %. In this
paper we report on the current-voltage characteristics of bi-layer devices
consisting of TiO2
and a conjugated polymer.
Several polymers with different optical bandgap were studied. The maximum
External Quantum Efficiency (EQE) of the devices is comparable, but
the PCE differs considerably (0.2-0.5%). The differences can for a large
part be explained by the differences in optical bandgap of the polymers.
It is shown that a low band gap is beneficial for the short circuit
current, but does not automatically result in a high PCE as relative
shifts of the highest occupied molecular orbital (HOMO) energy levels
of the polymers reduce the open circuit voltage (Voc). The calculations show that a PCE up to ~ 19 % can be achieved
using the maximum possible Voc and a fill
factor of 80%. Judicious engineering of material combinations is required
to achieve such a power output, and it expresses the need for a continuing
search on potentially low cost, efficient metal oxide/polymer BHJ tructures.
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