Post-deposition passivation of AgBiS nanocrystal inks for high-efficiency ultra-thin solar cells

• Published in: Energy & environmental science 2024-11, Vol.17 (22), p.8885-8892
• Main Authors: Oh, Jae Taek, Wang, Yongjie, Rodà, Carmelita, Mandal, Debranjan, Kumar, Gaurav, Whitworth, Guy Luke, Konstantatos, Gerasimos
• Format: Article
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d4ee03266g

Ternary chalcogenide AgBiS 2 nanocrystals (NCs) have emerged as a new environmentally friendly material for non-toxic solution-processed solar cells, with a record efficiency of ∼9%. To date, however, this has been achieved with NCs that undergo a ligand exchange process exclusively in the solid-state increasing the manufacturing complexity and cost. Improving surface passivation has been the main route towards high performance nanocrystal based solar cell devices, with current strategies relying on methods that only diversify the types of passivating ligands in solutions or stepwise ex situ additional ligand treatment. Herein, we report a post-deposition in situ passivation strategy for AgBiS 2 NC inks involving a multifunctional molecular agent that serves to provide effective colloidal dispersibility of the nanocrystal ink, as well as to passivate nanocrystal surfaces after film deposition via in situ dissociation of chloride ions as atomic surface passivants. We show that, upon improved colloidal dispersibility and surface passivation, AgBiS 2 NCs yield thin films free from morphological defects with low trap-state density and balanced charge carrier mobilities. As a result, this process leads to ultrathin-film solar cells with a fill-factor of 72% and a power conversion efficiency in excess of 10%, setting a new record for eco-friendly, solution-processed ultrathin solar cells. A post-deposition in situ passivation strategy using a multi-functional molecular agent is reported with enhanced colloidal dispersibility of an environmentally-friendly AgBiS 2 nanocrystal ink, achieving a PCE over 10% in a solar cell.