Inverted Polymer Solar Cells with Annealing-Free Solution-Processable NiO.

Area of Science:

• Materials Science
• Energy Science
• Nanotechnology

Background:

• Nickel oxide (NiO) is a promising p-type semiconductor with high stability for hole transport layers (HTLs) in organic solar cells.
• Current limitations include wettability issues with water-based solvents and high-temperature annealing requirements, hindering its widespread application.

Purpose of the Study:

• To develop an annealing-free, solution-processable method for depositing NiO nanoparticles (s-NiO) as an HTL.
• To address the wettability challenges associated with NiO deposition on hydrophobic surfaces.
• To evaluate the performance of s-NiO HTLs in both conventional and inverted non-fullerene polymer solar cells.

Main Methods:

• A mixed solvent system of DI water, isopropyl alcohol, and 2-butanol was employed to create a stable NiO nanoparticle suspension (s-NiO).
• The s-NiO suspension was solution-processed as an HTL in inverted and conventional non-fullerene polymer solar cells.
• Device performance was characterized and compared to state-of-the-art HTLs like MoO_x and PEDOT:PSS.

Main Results:

• The developed s-NiO HTL enabled efficient deposition on hydrophobic active layers, overcoming previous wettability problems.
• An inverted non-fullerene solar cell utilizing the s-NiO HTL achieved a high power conversion efficiency of 11.23%.
• The performance of devices with s-NiO HTLs was comparable to those using conventional MoO_x and PEDOT:PSS HTLs.

Conclusions:

• An annealing-free, solution-processable method for NiO HTL deposition has been successfully demonstrated.
• This approach significantly enhances the applicability of NiO in solution-processed organic solar cells.
• The developed s-NiO HTL offers a viable and efficient alternative for high-performance organic solar cell fabrication.