An antibonding valence band maximum enables defect-tolerant and stable GeSe photovoltaics.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33510157.
- Also identified by DOI 10.1038/s41467-021-20955-5 and PMC identifier 7844217.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
In lead-halide perovskites, antibonding states at the valence band maximum (VBM)-the result of Pb 6s-I 5p coupling-enable defect-tolerant properties; however, questions surrounding stability, and a reliance on lead, remain challenges for perovskite solar cells. Here, we report that binary GeSe has a perovskite-like antibonding VBM arising from Ge 4s-Se 4p coupling; and that it exhibits similarly shallow bulk defects combined with high stability. We find that the deep defect density in bulk GeSe is ~10<sup>12</sup> cm<sup>-3</sup>. We devise therefore a surface passivation strategy, and find that the resulting GeSe solar cells achieve a certified power conversion efficiency of 5.2%, 3.7 times higher than the best previously-reported GeSe photovoltaics. Unencapsulated devices show no efficiency loss after 12 months of storage in ambient conditions; 1100 hours under maximum power point tracking; a total ultraviolet irradiation dosage of 15 kWh m<sup>-2</sup>; and 60 thermal cycles from -40 to 85 °C.