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Achieving 6.7% Efficiency in P3HT/Indene-C70 Bisadduct Solar Cells through the Control of Vertical Volume Fraction Distribution and Optimized Regio-Isomer Ratios

Abstract:
Indene C60 and C70 bisadducts (IC60BA and IC70BA) have relatively high lowest unoccupied molecular orbital energies. In poly(3-hexylthiophene) (P3HT)-based polymer solar cells (PSCs), this produces an increase in open-circuit voltage (VOC) and power conversion efficiency (PCE). However, ICBA synthesis produces a mixture of regio-isomers with different indene spatial orientations (2, 5, and 12 o'clock) that alter the IC70BA molecular packing when mixed with P3HT. In this paper, how the IC70BA regio-isomerism affects the PSC performance is examined by investigating the molecular packing of P3HT:IC70BA layers with different regio-isomeric ratios. For the first time, non-destructive spectroscopic ellipsometry is used to investigate the effect of the fabrication conditions on the P3HT/IC70BA vertical volume fraction distribution and the results are attributed to the spatial arrangement of the regio-isomers. It is demonstrated that this unambiguously affects the PSC performance. As a result, record device efficiencies are repeatedly attained for standard architecture P3HT:IC70BA PSCs with photoactive areas of 0.43 cm2, achieving 5.9 (±0.4)% PCE (n = 15). With control of the IC70BA constituent, device PCEs vary from below 2.2% to peak values above 6.7%, among the highest recorded PCEs for a P3HT combination, highlighting the importance of the molecular phase separation for high-efficiency devices.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1002/aelm.201600362

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Institution:
University of Oxford
Division:
MPLS
Department:
Materials
Role:
Author
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Institution:
University of Oxford
Division:
MPLS
Department:
Materials
Role:
Author


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Grant:
FP7 SMARTONICS (Grant Agreement Number 310229


Publisher:
Wiley
Journal:
Advanced Electronic Materials More from this journal
Volume:
2
Issue:
12
Pages:
1600362
Publication date:
2016-11-15
Acceptance date:
2016-10-05
DOI:
ISSN:
2199-160X


Keywords:
Pubs id:
pubs:660158
UUID:
uuid:57be9da9-e686-49e7-af0d-bbf8a992d601
Local pid:
pubs:660158
Source identifiers:
660158
Deposit date:
2016-11-21
ARK identifier:

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