Stereo-Hindrance Induced Conformal Self-Assembled Monolayer for High Efficiency Inverted Perovskite Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Self-assembled monolayers (SAMs) are crucial for high-efficiency inverted perovskite solar cells (PSCs).
• Existing carbazole phosphonic acid SAMs suffer from aggregation, hindering uniform coverage and performance.
• This limits the potential of perovskite solar cells.

Purpose of the Study:

• To develop a novel, non-aggregating SAM for improved hole-selective contacts in inverted PSCs.
• To enhance the conformality and hole-extraction capabilities of the SAM layer.
• To boost the power conversion efficiency (PCE) and stability of PSCs.

Main Methods:

• Synthesis of a tert-butyl functionalized carbazole phosphonic acid SAM (tBu-4PACz).
• Incorporation of tBu-4PACz into a mixed SAM system for inverted PSCs.
• Characterization of SAM morphology, photovoltaic performance, and device stability.

Main Results:

• The tBu-4PACz SAM demonstrated excellent conformality, preventing aggregation.
• Inverted PSCs with tBu-4PACz achieved a record PCE of 26.25% with high fill factors (>86%).
• Devices maintained over 94.7% efficiency after 500 hours of continuous operation.

Conclusions:

• The bulky tert-butyl group effectively suppresses SAM aggregation, improving interfacial properties.
• The novel SAM facilitates efficient hole extraction and reduces recombination losses.
• This advancement offers a pathway to highly efficient and stable perovskite solar cells.