Fine-Tuned Carbazole-Based Polymers with Controlled Connectivity as Efficient Interfacial Layers in Perovskite Solar...

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Perovskite solar cells (PSCs) face efficiency losses due to interfacial issues.
• Strategic molecular design of interfacial layers is crucial for mitigating these losses.

Purpose of the Study:

• To investigate the impact of molecular connectivity in carbazole-based polymers on interfacial properties in PSCs.
• To engineer polymers for enhanced perovskite surface passivation and reduced recombination.

Main Methods:

• Synthesis of two carbazole-based polymers with distinct connectivity patterns (3,6-3,6-Cbz and 3,6-2,7-Cbz).
• Structure-property analysis including XPS and SCLC characterization.
• Fabrication and testing of planar n-i-p PSC devices using these polymers as interfacial modifiers.

Main Results:

• The 3,6-2,7-Cbz polymer demonstrated superior π-electron delocalization and energy level alignment.
• This polymer achieved excellent perovskite surface defect passivation and suppressed interfacial recombination.
• A champion device efficiency of 24.16% was achieved with the 3,6-2,7-Cbz polymer, outperforming control and analogue materials.
• High performance (23.17% PCE) was maintained even with undoped carbazole hole transport layers (HTLs).

Conclusions:

• Molecular topology significantly influences interfacial phenomena and device performance in PSCs.
• The 3,6-2,7-Cbz polymer represents a versatile and effective interfacial material for high-performance PSCs.
• This study provides fundamental insights into engineering interfacial layers for next-generation photovoltaics.