Misconceptions and Misnomers in Solar Cells

Some of the terms that are currently used in solar cell technology, such as “emitter” and “back surface field,” perpetuate old misconceptions about the role of the highly doped n⁺ and p⁺ regions commonly implemented near their front and back surfaces. This paper reviews the physics of the p⁺ back surface region of silicon solar cells and concludes that, whereas electric fields are important to describe equilibrium conditions, the main force behind carrier transport under illumination is the gradient of the carrier concentration itself, i.e., of the chemical potential. The function of the back p⁺ region in a photovoltaic device is to facilitate the transfer of holes toward the metal contact, while suppressing the concentration of electrons. An appropriate name for it is hole collector. Similarly, the function of the n⁺ region is to collect and transfer electrons to the front metal contact and should be called the electron collector.