Premium
Impact of Triplet Excited States on the Open‐Circuit Voltage of Organic Solar Cells
Author(s) -
Benduhn Johannes,
Piersimoni Fortunato,
Londi Giacomo,
Kirch Anton,
Widmer Johannes,
Koerner Christian,
Beljonne David,
Neher Dieter,
Spoltore Donato,
Vandewal Koen
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201800451
Subject(s) - materials science , excited state , acceptor , photovoltaic system , coupling (piping) , organic solar cell , voltage , atomic physics , open circuit voltage , photochemistry , charge (physics) , optoelectronics , triplet state , chemical physics , physics , chemistry , condensed matter physics , polymer , quantum mechanics , metallurgy , composite material , ecology , biology
The best organic solar cells (OSCs) achieve comparable peak external quantum efficiencies and fill factors as conventional photovoltaic devices. However, their voltage losses are much higher, in particular those due to nonradiative recombination. To investigate the possible role of triplet states on the donor or acceptor materials in this process, model systems comprising Zn‐ and Cu‐phthalocyanine (Pc), as well as fluorinated versions of these donors, combined with C 60 as acceptor are studied. Fluorination allows tuning the energy level alignment between the lowest energy triplet state (T 1 ) and the charge‐transfer (CT) state, while the replacement of Zn by Cu as the central metal in the Pcs leads to a largely enhanced spin–orbit coupling. Only in the latter case, a substantial influence of the triplet state on the nonradiative voltage losses is observed. In contrast, it is found that for a large series of typical OSC materials, the relative energy level alignment between T 1 and the CT state does not substantially affect nonradiative voltage losses.