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Open‐Circuit Voltage and Effective Gap of Organic Solar Cells
Author(s) -
Widmer Johannes,
Tietze Max,
Leo Karl,
Riede Moritz
Publication year - 2013
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201301048
Subject(s) - acceptor , materials science , ionization energy , band gap , open circuit voltage , solar cell , ionization , organic solar cell , electron affinity (data page) , active layer , electron acceptor , heterojunction , doping , analytical chemistry (journal) , molecule , optoelectronics , layer (electronics) , voltage , nanotechnology , photochemistry , condensed matter physics , chemistry , ion , polymer , organic chemistry , physics , thin film transistor , quantum mechanics , composite material
The open‐circuit voltage ( V OC ) of an organic solar cell is limited by the donor‐acceptor material system. The effective gap E g eff between the electron affinity of the acceptor and the ionization potential of the donor is usually regarded as the upper limit for V OC , which is only reached for T → 0 K. This relation is confirmed for a number of small‐molecule bulk heterojunction p‐i‐n type solar cells by varying the temperature and illumination intensity. With high precision, the low temperature limit of V OC is identical to E g eff . Furthermore, the influence of the hole transport material in a p‐doped hole transport layer and the donor‐acceptor mixing ratio on this limit V 0 is found to be negligible. Varying the active material system, the quantitative relation between V 0 and E g eff is found to be identity. A comparison of V 0 in a series of nine different donor‐acceptor material combinations opens a pathway to quantitatively determine the ionization potential of a donor material or the electron affinity of an acceptor material.