AVS 65th International Symposium & Exhibition | |
Thin Films Division | Monday Sessions |
Session TF-MoA |
Session: | IoT Session: Thin Films for Photovoltaics |
Presenter: | Thomas Riedl, University of Wuppertal, Germany |
Correspondent: | Click to Email |
Organic and perovskite based solar cells (OSCs / PSCs) provide an intriguing avenue for next-generation thin-film photovoltaics. Aside from the photo-active material, the choice of charge extraction layers (CELs) substantially impacts performance and lifetime. For OSCs, the use of ALD-grown tin-oxide (SnOx) as electron extraction layer (EEL) mitigates two critical issues, i.e. light soaking[1] and photo-shunting[2], which frequently occur in case ZnO based EELs are used. In tandem OSCs, all-oxide recombination interconnects based on high work-function (WF) MoOx and low-WF ALD grown SnOx show ideal alignment of the conduction band of MoOx and SnOx and loss-free addition of the open circuit voltages of the two sub-cells.[3]
In the second part, I will show ALD-grown SnOx as impermeable EEL for PSCs to enable impressive stability of the cell against heat and moisture. The SnOx is positioned between the metal electrode and the perovskite. Its outstanding permeation barrier properties[4] protect the MAPbI3 against the ingress of moisture or migrating metal atoms, while simultaneously the metal electrode is protected against leaking halide compounds. Thereby, PSCs with an efficiency of >20% and outstanding long-term stability can be achieved. They remain stable over 4500 hours at elevated temperatures as well as in ambient air. [5,6] ALD-grown SnOx is also excellently suited to sandwich and protect ultra-thin metal layers (Ag or Cu) as cost efficient Indium-free semitransparent electrodes (SnOx/metal/SnOx) in PSCs. Using photoelectron spectroscopy, we unravel the formation of a PbI2 interfacial layer between a SnOx EEL and the perovskite. The resulting interface dipole between SnOx and the PbI2 depends on the choice of oxidant for ALD (water, ozone, oxygen plasma). SnOx grown by using ozone affords hysteresis-free devices with a stable efficiency of 16.3% and a very high open circuit voltage of 1.17 V.[7] Ultimately, SnOx grown by spatial-ALD at atmospheric pressure is presented. Its suitability to replace its low pressure analogues in PSCs is shown. [1, 2] This work paves the way towards roll-to-roll fabrication of stable, Indium-free PSCs.
[1] S. Trost et al., Adv. Energy Mater.2015, 5, 1500277.
[2] S. Trost et al., Adv. Energy Mater.2016, 6, 1600347.
[3] T. Becker et al., Adv. Energy Mater.2018, 8, 1702533.
[4] A. Behrendt et al., Adv. Mater.2015, 27, 5961.
[5] K. O. Brinkmann et al., Nat. Comms.2017, 8, 13938.
[6] J. Zhao et al., Adv. Energy Mater.2017, 7, 1602599.
[7] T. Hu et al., Adv. Mater.2017, 29, 1606656.
[8] L. Hoffmann et al., J. Vac. Sci. & Technol. A2018, 36, 01A112.
[9] L. Hoffmann et al., ACS Appl. Mater. & Interf.2018, 10, 6006.