This paper examines the biological process of photosynthesis and its relationship to solar photovoltaic (PV) technology. It explains how plants use chlorophyll to convert sunlight into chemical energy in the form of sugars, and how PV cells artificially replicate this conversion to produce electricity. Drawing on sources including the Handbook of Photovoltaic Science and Engineering, the paper outlines the three phases of photosynthesis, describes the molecular mechanisms underlying both systems, and compares them across several dimensions — including energy storage, output type, and evolutionary origin. The paper concludes that while the two systems differ significantly in method and output, both are central to the future of sustainable energy production.
Photosynthesis is the process by which green plants create their own food using sunlight. Unlike animals, which must consume other organisms for their nutrient intake, plants produce food internally thanks to a pigment called chlorophyll. Chlorophyll gives plants their green color and "captures the Sun's energy and uses it to make sugars out of carbon dioxide from the air and water" (University, 2008). These sugars are vital because they serve as fuel for the plant's roots, stems, and leaves, enabling continued growth.
Once the plant has produced sufficient food through sunlight to sustain a healthy condition, it releases oxygen into the air — the same oxygen that humans and animals depend on to breathe and survive.
In the Handbook of Photovoltaic Science and Engineering, the authors describe photosynthesis as occurring in three distinct phases: (a) "light harvesting by antenna systems"; (b) "conversion of excitonic energy to chemical energy"; and (c) "synthesis and export of products" — that is, the release of oxygen (Luque, 2011).
The conversion of sunlight into electricity is a process known as photovoltaic (PV) technology. In essence, it is an artificial strategy designed to replicate what photosynthesis accomplishes in the natural world (Luque, 2011). In nature, light is converted into chemical energy through: (a) the "proximal location of molecular components"; (b) energy received in "excited states"; and (c) the precise "time, concerning the rates of competing processes" (Luque, 2011). In PV technology, sunlight strikes solar cells and, through artificial "bonding strategies" that are both "covalent and non-covalent," electricity is produced.
Author Tetsuo Soga notes that "the physics of organic PV cells is much closer to that other, much older and more sophisticated, example of organic electronics: photosynthesis" (Mapel et al., 2007, p. 335). Indeed, photosynthetic plants and bacteria are known to "utilize organic molecules similar to those used in organic PV"; in other words, semiconductor PV structures mimic the process of natural photosynthesis.
"Side-by-side similarities and differences of both systems"
Photosynthesis provides stored chemical potential in the form of sugars that fuel plant growth. Photovoltaic technologies, by contrast, do not inherently store energy — they provide "instantaneous electrical power," which may be stored separately, but at the moment sunlight strikes the cell, electricity is produced (Green, 2011, p. 1). That said, the hydrogen produced through photovoltaic technologies is "thermodynamically equivalent to the sugar produced by photosynthesis" (Green, 2011, p. 1), which represents a meaningful similarity between the two systems.
Photovoltaic technologies rely on "fundamental principles combined with advances in materials" to complete solar-to-electrical power conversion and enable "hydrogen production from water electrolysis." Photosynthesis, by contrast, "originated in an environment… and provided for early life forms as a means of self-contained energy production" (Green, 2011, p. 1). One system was engineered; the other evolved.
Looking ahead, because the future of energy production in society will increasingly move away from oil and coal toward solar sources, both photosynthesis and photovoltaic technologies are becoming — and will continue to be — pivotal to the survival of humans, animals, and plant species alike.
There are clearly both differences and similarities between photosynthesis and the photovoltaic technologies now being built and marketed. The future of electrical energy will be solar, while the future of photosynthesis will closely mirror its long history. While one system is still being refined — photovoltaics — the other, photosynthesis, has been in operation since the earliest stages of Earth's development.
Green, Jenny. (2011). Photosynthesis or photovoltaics: Weighing the impact. ASU News [Now]. Arizona State University. Retrieved October 29, 2012, from
Luque, Antonio, and Hegedus, Steven. (2011). Handbook of Photovoltaic Science and Engineering. Hoboken, NJ: John Wiley & Sons.
Mapel, J.K., and Baldo, M.A. (2007). "The Application of Photosynthetic Materials and Architectures to Solar Cells," in Nanostructured Materials for Solar Energy Conversion, T. Soga, Ed. Washington, D.C.: Elsevier.
[University]. (2008). How does photosynthesis work? Wonders of Our World. Retrieved October 29, 2012, from
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