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Achieving 6.7% Efficiency in P3HT/Indene‐C 70 Bisadduct Solar Cells through the Control of Vertical Volume Fraction Distribution and Optimized Regio‐Isomer Ratios
Author(s) -
Kutsarov Dimitar I.,
Rašović Ilija,
Zachariadis Alexandros,
Laskarakis Argiris,
Lebedeva Maria A.,
Porfyrakis Kyriakos,
Mills Christopher A.,
Beliatis Michail J.,
Fisher Brett,
Bruchlos Kirsten,
Ludwigs Sabine,
Logothetidis Stergios,
Silva S. Ravi P.
Publication year - 2016
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201600362
Subject(s) - materials science , indene , energy conversion efficiency , homo/lumo , volume fraction , phase (matter) , analytical chemistry (journal) , chemical engineering , molecule , optoelectronics , organic chemistry , chemistry , composite material , engineering
Indene C 60 and C 70 bisadducts (IC 60 BA and IC 70 BA) 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 ( V OC ) 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 IC 70 BA molecular packing when mixed with P3HT. In this paper, how the IC 70 BA regio‐isomerism affects the PSC performance is examined by investigating the molecular packing of P3HT:IC 70 BA 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/IC 70 BA 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:IC 70 BA PSCs with photoactive areas of 0.43 cm 2 , achieving 5.9 (±0.4)% PCE ( n = 15). With control of the IC 70 BA 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.