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HL: Fachverband Halbleiterphysik

HL 27: Focus Session: Perspectives in Cu(In,Ga)Se 1

HL 27.4: Vortrag

Donnerstag, 8. September 2022, 10:45–11:00, H33

Electronic properties of the back contact in Cu(In,Ga)Se2 solar cells — Torsten Hölscher, Thomas Schneider, Merve Demir, Julia Horstmann, Melina Kristen, Heiko Kempa, and •Roland Scheer — Martin-Luther-Universität Halle/Wittenberg, Naturwissenschaftliche Fakultät II, Institut für Physik, Fachgruppe Photovoltaik, Von-Danckelmann-Platz 3, 06120 Halle/Saale

Cu(In,Ga)Se2 solar cells are interesting for single junction and multi-junction (tandem) photovoltaic energy conversion. Although not being ideal, their back contact may exhibit a secondary junction. This is the case for low bandgap Cu(In,Ga)Se2 with a molybdenum back contact. Here, the secondary junction leads to a certain admittance step, a saturation in the Voc(T) plot, but has little impact on the device performance for thick Cu(In,Ga)Se2 layers: The barrier typically is small enough to allow for majority carrier transport and sufficiently far away from the main junction to impede minority carrier recombination. Only for ultrathin Cu(In,Ga)Se2 solar cells, the barrier can limit the device performance. For wide bandgap Cu(In,Ga)Se2 on molybdenum, the barrier appears to be even smaller. The situation is much less clear for Cu(In,Ga)Se2 on a transparent ITO back contact for tandem applications. For low bandgap Cu(In,Ga)Se2, no barrier is to be detected by admittance and Voc(T) experiments. For widegap Cu(In,Ga)Se2, the barrier formation in addition depends on the type of dopant. In this contribution, we used different experimental techniques in order to develop electronic models for opaque (Molybdenum) and transparent (ITO) back contacts.