Open-circuit voltage and effective gap of organic solar cells

Journal article

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 V₀ is found to be negligible. Varying the active material system, the quantitative relation between V₀ and E_g^eff is found to be identity. A comparison of V₀ 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. © 2013 WILEY-VCH Verlag GmbH and Co.

Authors: Widmer, J; Tietze, M; Leo, K; Riede, M

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Advanced Functional Materials
• Volume: 23
• Issue: 46
• Pages: 5814–5821
• Publication date: 2013-01-01
• DOI: 10.1002/adfm.201301048
• EISSN: 1616-3028
• ISSN: 1616-301X
• Language: English
• Keywords: solar cells; thin films; photovoltaic devices; characterization tools; organic electronics