Hierarchical Solid-Additive Strategy for Achieving Layer-by-Layer Organic Solar Cells with Over 19 % Efficiency.

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Layer-by-layer (LbL) deposition in organic solar cells (OSCs) offers precise control over active layer properties.
• Achieving high-performance LbL OSCs with multiple distinct solid additives in each layer presents significant challenges.

Purpose of the Study:

• To investigate a novel strategy for incorporating different solid additives into specific layers of LbL organic solar cells.
• To enhance the performance of OSCs by improving charge carrier mobility and suppressing recombination through targeted additive placement.

Main Methods:

• Incorporation of FeCl3 as a p-type dopant into the donor (D18) layer to boost hole concentration and mobility.
• Addition of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) into the acceptor (L8-BO) layer to enhance morphology and exciton lifetime.

Main Results:

• A D18+FeCl3/L8-BO device achieved a power conversion efficiency (PCE) of 18.12%, and a D18/L8-BO+PFO device reached 18.79%.
• The combined strategy in the D18+FeCl3/L8-BO+PFO device resulted in a remarkable PCE of 19.17%, surpassing the control device's 17.59%.
• The layered additive approach improved electron and hole mobility, suppressed charge recombination, and did not negatively impact the open-circuit voltage.

Conclusions:

• The strategic incorporation of distinct solid additives in specific layers of LbL OSCs is an effective method for performance enhancement.
• This layered solid additive strategy offers a promising pathway for developing high-efficiency organic solar cells.