Published in Advanced Functional Materials: Oxygen-containing groups as a key to enable high-efficiency (certificed 26.35%) and high-stability (≥1100 hours) PV cells

Congratulations, Yiqing, on your outstanding achievment as a first-year PhD student! Perovskites like oxygen, so we can feed them before they have the chance to capture the free-state oxygen and become unstable. By providing stable, compound-state oxygen to the uncoordinated Pb and FA molecules and forming strong bonds such as Pb-O, we have achieved high-efficiency (certified 26.35%) and high-stability (T₉₅≥1100h under one-sun continuous illumination, 40 ℃, RH 35%, V_mpp tracking) perovskite solar cells.

Abstract: The characteristics of perovskite solution processing inherently led to the formation of lattice defects during fabrication, such as lead and iodine vacancies. These defects significantly hinder the efficiency and stability of perovskite solar cells (PSCs), posing a major obstacle to their commercialization. Herein, a bifunctional ligand, N-hydroxymethyl succinimide (NHMS), containing both Lewis base groups (C=O) and proton donor groups (−OH), is introduced to improve the crystal quality of perovskite films and enhance photovoltaic performance. Theoretical calculations and experimental results reveal that NHMS effectively passivates bulk and interfacial defects by coordinating with uncoordinated lead ions (Pb²⁺) and forming hydrogen bonds with iodide or formamidinium ions (I^-/FA⁺). This dual-site passivation effect effectively reduces trap-assisted recombination. Moreover, the incorporation of NHMS promotes the oriented crystallization of the perovskite, leading to a notable increase in grain size. Consequently, NHMS-treated PSCs achieved a champion power conversion efficiency (PCE) of 26.51% (certified 26.35%), while centimeter-sized PSCs exhibited an impressive PCE of 25.15%. Furthermore, The NHMS-treated device exhibits a remarkable stability for maintaining 95% of its initial efficiency after 1100 hours of maximum power point voltage tracking. This work provides comprehensive insights into the application of dual-site passivation to achieve high-performance PSCs.

This work is published in Advanced Functional Materials.

Acknowledgement

This work is a result of close collaboration of experimentalists (Prof Jun Peng’s group) and theorists (the nexSAS group). We acknowledge the financial support from ACAP and the computational resource from the Pawsey supercomputing centre of Australia.