CASE STUDY – SEMICONDUCTORS
Low temperature ALD growth optimization of ZnO, TiO2, and Al2O3 to be used as a buffer layer in perovskite solar cells
Authors: Pravakar Rajbhandari and Tara Dhakal
Institution: Binghamton University
Application: Solar Energy; Semiconductors
Summary: Organic materials provide a very small thermal budget for any postfabrication treatment or for a subsequent layer in a device fabrication. This demand for the low-temperature process has driven the focus of this study to obtain atomic layer deposited oxide layer at a low temperature suitable for a buffer layer in perovskite solar cells. The buffer layer will assist in blocking holes, effectively extract electrons, provide better shunt protection, and act as a sputter protection layer for organic perovskites. Three different oxide layers, Al2O3, ZnO, and TiO2, are grown at 100 °C and studied for this purpose using synchronous modulated flow draw atomic layer deposition (ALD) technology optimized in a commercial 200 mm ALD reactor. It allows greater precursor utilization and shorter deposition cycle times that in turn reduces thermal processing time compared to traditional ALD processes.
Key Takeaways:
- An ultrathin bilayer of ZnO and Al2O3 deposited on 200 mm wafers increased the power conversion efficiency of a perovskite solar cell to 17.5%.
- Oxide thin films were shown to enhance the fill factor and charge extraction of the solar cell.
- Dynamic pressure control and fast pneumatic valving in the tool offered fast cycle times even at low temperatures when thermal budget and surface damage is a concern.
Read the Full Paper: https://doi.org/10.1116/1.5139247
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