Solution-processed all-oxide bulk heterojunction solar cells based on CuO nanaorod array and TiO₂ nanocrystals

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Developing efficient solar cells is crucial for renewable energy.
• Bulk heterojunctions (BHJs) offer potential for enhanced light absorption and charge separation.
• Understanding interfacial charge dynamics is key to optimizing BHJ solar cell performance.

Purpose of the Study:

• To synthesize a CuO nanorod array/TiO2 nanocrystals bulk heterojunction (BHJ) on FTO glass.
• To investigate the interfacial charge transfer mechanisms in this BHJ using Kelvin probe force microscopy (KPFM).
• To identify the factors limiting the performance of fabricated solar cells and propose optimization strategies.

Main Methods:

• Hydrothermal synthesis of single-crystalline p-type CuO nanorod arrays on FTO glass.
• Filling n-type TiO2 precursor into CuO nanorods followed by air annealing to form nano-interpenetrating BHJ.
• Utilizing KPFM to study interface charge transfer and surface potential variations under illumination.
• Fabricating and characterizing solar cells with the structure FTO/CuO nanoarray/TiO2/Al.

Main Results:

• Successfully fabricated CuO nanorod array/TiO2 nanocrystals BHJ solar cells.
• KPFM confirmed photo-generated electron transfer from CuO to TiO2.
• The fabricated solar cell exhibited low performance (Voc = 0.20 V, Jsc = 0.026 mA cm-2).
• Analysis revealed unsatisfactory electron injection efficiency from CuO to TiO2 due to limited electron concentration change in TiO2.

Conclusions:

• The low solar cell performance is attributed to undesirable interface charge transfer and inefficient electron injection.
• The small interfacial surface potential difference between CuO and TiO2 limits the open-circuit voltage.
• Improving interfacial electron injection is critical for enhancing the efficiency of CuO nanorod array/TiO2 heterojunction solar cells.