The role of spin in the degradation of organic photovoltaics

Stability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet...

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Main Authors: Ramirez, I, Privitera, A, Karuthedath, S, Jungbluth, A, Benduhn, J, Sperlich, A, Spoltore, D, Vandewal, K, Laquai, F, Riede, M
Format: Journal article
Sprog:English
Udgivet: Springer Nature 2021
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author Ramirez, I
Privitera, A
Karuthedath, S
Jungbluth, A
Benduhn, J
Sperlich, A
Spoltore, D
Vandewal, K
Laquai, F
Riede, M
author_facet Ramirez, I
Privitera, A
Karuthedath, S
Jungbluth, A
Benduhn, J
Sperlich, A
Spoltore, D
Vandewal, K
Laquai, F
Riede, M
author_sort Ramirez, I
collection OXFORD
description Stability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet oxygen production or fullerene dimerization. The latter is thought to proceed from unquenched singlet excitons that have undergone intersystem crossing (ISC). Instead, we show that in bulk heterojunction (BHJ) solar cells the photo-degradation of C<sub>60</sub> via photo-oligomerization occurs primarily via back-hole transfer (BHT) from a charge-transfer state to a C<sub>60</sub> excited triplet state. We demonstrate this to be the principal pathway from a combination of steady-state optoelectronic measurements, time-resolved electron paramagnetic resonance, and temperature-dependent transient absorption spectroscopy on model systems. BHT is a much more serious concern than ISC because it cannot be mitigated by improved exciton quenching, obtained for example by a finer BHJ morphology. As BHT is not specific to fullerenes, our results suggest that the role of electron and hole back transfer in the degradation of BHJs should also be carefully considered when designing stable OPV devices.
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spelling oxford-uuid:a00d1a16-3c20-45da-b5a6-97d2fd6d54a52022-03-27T02:02:36ZThe role of spin in the degradation of organic photovoltaicsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:a00d1a16-3c20-45da-b5a6-97d2fd6d54a5EnglishSymplectic ElementsSpringer Nature2021Ramirez, IPrivitera, AKaruthedath, SJungbluth, ABenduhn, JSperlich, ASpoltore, DVandewal, KLaquai, FRiede, MStability is now a critical factor in the commercialization of organic photovoltaic (OPV) devices. Both extrinsic stability to oxygen and water and intrinsic stability to light and heat in inert conditions must be achieved. Triplet states are known to be problematic in both cases, leading to singlet oxygen production or fullerene dimerization. The latter is thought to proceed from unquenched singlet excitons that have undergone intersystem crossing (ISC). Instead, we show that in bulk heterojunction (BHJ) solar cells the photo-degradation of C<sub>60</sub> via photo-oligomerization occurs primarily via back-hole transfer (BHT) from a charge-transfer state to a C<sub>60</sub> excited triplet state. We demonstrate this to be the principal pathway from a combination of steady-state optoelectronic measurements, time-resolved electron paramagnetic resonance, and temperature-dependent transient absorption spectroscopy on model systems. BHT is a much more serious concern than ISC because it cannot be mitigated by improved exciton quenching, obtained for example by a finer BHJ morphology. As BHT is not specific to fullerenes, our results suggest that the role of electron and hole back transfer in the degradation of BHJs should also be carefully considered when designing stable OPV devices.
spellingShingle Ramirez, I
Privitera, A
Karuthedath, S
Jungbluth, A
Benduhn, J
Sperlich, A
Spoltore, D
Vandewal, K
Laquai, F
Riede, M
The role of spin in the degradation of organic photovoltaics
title The role of spin in the degradation of organic photovoltaics
title_full The role of spin in the degradation of organic photovoltaics
title_fullStr The role of spin in the degradation of organic photovoltaics
title_full_unstemmed The role of spin in the degradation of organic photovoltaics
title_short The role of spin in the degradation of organic photovoltaics
title_sort role of spin in the degradation of organic photovoltaics
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