Towards low-temperature processing of efficient $\gamma$-CsPbI$_3$ perovskite solar cells

• Main Authors: Zhang, Zongbao, Ji, Ran, Hofstetter, Yvonne J, Deconinck, Marielle, Brunner, Julius, Li, Yanxiu, An, Qingzhi, Vaynzof, Yana
• Format: Journal Article
• Language: English
• Published: 17-04-2024
• Subjects: Physics - Materials Science
• DOI: 10.48550/arxiv.2404.11636

Inorganic cesium lead iodide (CsPbI$_3$) perovskite solar cells (PSCs) have
attracted enormous attention due to their excellent thermal stability and
optical bandgap (~1.73 eV), well-suited for tandem device applications.
However, achieving high-performing photovoltaic devices processed at low
temperatures is still challenging. Here we reported a new method to fabricate
high-efficiency and stable $\gamma$-CsPbI$_3$ PSCs at lower temperatures than
was previously possible by introducing the long-chain organic cation salt
ethane-1,2-diammonium iodide (EDAI2) and regulating the content of lead acetate
(Pb(OAc)2) in the perovskite precursor solution. We find that EDAI2 acts as an
intermediate that can promote the formation of $\gamma$-CsPbI$_3$, while excess
Pb(OAc)2 can further stabilize the $\gamma$-phase of CsPbI$_3$ perovskite.
Consequently, improved crystallinity and morphology and reduced carrier
recombination are observed in the CsPbI$_3$ films fabricated by the new method.
By optimizing the hole transport layer of CsPbI$_3$ inverted architecture solar
cells, we demonstrate up to 16.6% efficiencies, surpassing previous reports
examining $\gamma$-CsPbI$_3$ in inverted PSCs. Notably, the encapsulated solar
cells maintain 97% of their initial efficiency at room temperature and dim
light for 25 days, demonstrating the synergistic effect of EDAI2 and Pb(OAc)2
on stabilizing $\gamma$-CsPbI$_3$ PSCs.