Alleviating Defect and Oxidation in Tin Perovskite Solar Cells Using a Bidentate Ligand

Abstract

Tin-perovskite solar cells (Sn-PSCs) have low energy conversion efficiency and stability due to facile oxidation of Sn2+ during precursor solution preparation and film growth. Herein, we introduced formohydrazide (FHZ) as a bidentate ligand into the Sn-halide perovskite (Sn-HaP) to improve the optoelectronic properties. This approach is found to be effective for the suppression of Sn-oxidation and interfacial energy band modulation. The depth profile distribution confirmed that the FHZ additive is primarily located on surfaces and the hole transport layer (HTL)/Sn-HaP interface with partly capping at the grain boundaries, which offers a reducing ambient in the Sn-HaP film. Therefore, the device with FHZ demonstrated a device efficiency of 12.87% (9.93% control) with enhanced open circuit voltage from ∼0.734 to 0.874 V and improved operational device stability. The device analysis suggests that the FHZ additive alleviates the bulk and interface defect in the Sn-PSC with −NH2 and −O═C bidentate bonding to Sn-HaP, which is supported by theoretical calculations. Thus, this work corroborates the importance of multidentate ligands for modulating the film morphology and defect chemistry in the Sn-perovskite for high efficiency and superior device stability.

Terumasa Tadano

Researcher of Materials Science

My research interests include development of computational methods and softwares for predicting thermal properties of solids, and application of machine-learning methods to material science study