Spiro-Phenothiazine Hole-Transporting Materials: Unlocking Stability and Scalability in Perovskite Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Perovskite solar cells (PSCs) require efficient and stable hole-transporting materials (HTMs) for commercialization.
• Spiro-OMeTAD, a common HTM, suffers from doping inhomogeneity and poor stability, limiting large-scale PSC applications.

Purpose of the Study:

• To develop novel spiro-phenothiazine-based HTMs (PTZ) to overcome the limitations of spiro-OMeTAD.
• To evaluate the performance and stability of PSCs utilizing the new PTZ-based HTMs, particularly the fluorene derivative (PTZ-Fl).

Main Methods:

• Synthesis and characterization of a series of spiro-phenothiazine-based HTMs.
• Fabrication and testing of PSCs incorporating the PTZ-based HTMs.
• Assessment of device efficiency (PCE) and long-term operational stability under various protocols (ISOS-L-3, ISOS-D-1).

Main Results:

• The PTZ-Fl HTM demonstrated enhanced Li+ affinity, forming a stable interphase that inhibited Li+ migration.
• PSCs with PTZ-Fl achieved high power conversion efficiencies (PCEs) up to 25.8% (certified 25.2%).
• PTZ-Fl based PSCs retained 80% of initial performance after 1000 h (ISOS-L-3), and a 5x5 cm mini-module retained over 85% efficiency after 1100 h (ISOS-D-1).

Conclusions:

• Spiro-phenothiazine-based HTMs, particularly PTZ-Fl, offer a viable alternative to spiro-OMeTAD for high-performance PSCs.
• PTZ-Fl significantly enhances both the power conversion efficiency and operational stability of perovskite solar cells.
• These findings represent a promising advancement for the commercial viability of next-generation perovskite solar technologies.