With the increasing demand for energy, the supply rate is expected to decline in the near future. As fossil fuel reserves are rapidly depleting, the low efficiency of energy conversion and recycling, along with the complex technologies and high costs of solar cells, have become the most limiting factors for solar cells. Nanotechnology has brought remarkable advancements to human lifestyles, and we can utilize nanotechnology for green energy purposes and the construction of renewable energy systems. Nowadays, bio-nano materials (biological nanomaterials) encompass a broader scope of nanotechnology and are demonstrating their incredible impacts in reducing various short-term and long-term hazardous challenges. One of the reasons solar energy has become very popular is its cost-effectiveness, low maintenance, and reliability as an energy source. Affordable and environmentally friendly natural materials have replaced many of the chemical substances used in solar cells as light harvesters. Additionally, hybrid biological materials in semiconductor solar cells are capable of providing high efficiency. Various bio-nanomaterials such as nanocellulose, bacteriorhodopsin proteins, and organic piezoelectric and thermoelectric biomaterials are being investigated as next-generation solar cell materials. Solar cells sensitized with biological molecules have also gained popularity as cost-effective photovoltaic generators, addressing their recycling issues. The main reason for using plant materials in solar cells is the need to replace expensive, energy-intensive, scarce, or non-renewable components.