Co-Sensitized Solar Cell Achieves 13.7% Efficiency with Bis-Hexylthiophene Dyes

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Dye-sensitized solar cells (DSCs) require efficient light harvesting and suppressed charge recombination for high performance.
• Organic photosensitizers are crucial components in DSCs, influencing open-circuit photovoltage (V_oc) and overall efficiency.
• Molecular design of photosensitizers, including alkyl chain length, impacts excited-state lifetimes and device performance.

Purpose of the Study:

• To develop novel organic photosensitizers (H6 and H7) for enhanced dye-sensitized solar cells (DSCs).
• To investigate the effect of varying alkyl chain lengths in photosensitizers on excited-state lifetimes and photovoltaic performance.
• To achieve high open-circuit photovoltage (V_oc) and power conversion efficiency (PCE) in DSCs.

Main Methods:

• Synthesis of two organic photosensitizers, H6 and H7, with differing alkyl chain lengths.
• Fabrication of dye-grafted titania and alumina films to study excited-state lifetimes.
• Construction and testing of copper-based DSCs and co-sensitized devices with XY1b under simulated AM1.5 G conditions.

Main Results:

• Photosensitizer H7, with longer alkyl chains, exhibited longer excited-state lifetimes compared to H6.
• A copper-based DSC using H7 achieved a high V_oc of 1.22 V.
• The co-sensitized device with H7 and XY1b demonstrated a fill factor of 82.1% and a PCE of 13.7%; efficiencies up to 29.7% were achieved under dim light.

Conclusions:

• Longer alkyl chains in organic photosensitizers can enhance excited-state lifetimes and improve DSC performance.
• The developed photosensitizers show potential for high-efficiency solar energy conversion, comparable to perovskite solar cells.
• The study highlights the importance of molecular engineering in organic photosensitizers for advanced photovoltaic applications.