More efficient solar cells thanks to nanowires

Cells or solar cells, intermediaries that convert sunlight into electricity, are one of the most relevant alternative energy mechanisms in the world, which is why they are constantly looking for ways to make them more efficient. An investigation proposes a model that could be the first step to design them using wires imperceptible to the human eye (nanowires).

A solar panel or plate is made up of between 30 and 70 solar cells –depending on the manufacturer–, and each of them is made up of two semiconductors, one with a positive charge –holes– and the other with a negative charge –electrons.

Physicist Christian Joven, a student in the Master’s program in Physical Sciences at the National University of Colombia (UNAL) in Manizales, points out that solar cells are usually flat, a characteristic that decreases their effectiveness in capturing sunlight.

In his research, he designed a mathematical model that would allow the development of nanowire solar cells – nanometer-scale cables, imperceptible to the human eye, that conduct electricity – whose radial shape with a circumference, similar to a sphere, would facilitate greater use of the light.

“The research showed that the absorption of light in a nanowire can be greater due to the reduction of light reflection, a phenomenon that occurs when rays collide with a surface, are deflected and return to the medium from which they came”, explains the young student, who is part of the seedbed “New materials and renewable energy”, of the Institute of Studies of the Orinoquia.

Professor Roberto Bernal, from UNAL Orinoquia Headquarters, co-director of the research work, clarifies that “until now, nanowire cells are only experimental, not commercial. However, the approach to the subject made by the young student allows us to recommend a possible alternative to develop this type of device in the future”.

Professor and student note that the study is in the first phase, and the second would focus on “finding the current density and the efficiency of the devices.”

“The theory that describes physical phenomena to optimize parameters (in terms of nanowire cells) is scarce; That is why this first mathematical approach is important, because analytical solutions cannot be given as in flat cells; in fact, one of the parameters used is given in a space-charge relationship”, assures the master’s student.

A solar panel of the most common size is made up of between 30 and 70 solar cells, depending on the manufacturer. (Photo: Unimedios / UNAL)

To advance the investigation, a quantitative design was used that allowed evaluating the relationship between the different variables considered, such as the absorption of light, refraction (change of direction experienced by a wave when passing from one material medium to another) and the efficiency. First, the Poisson differential equation, used in different fields, including physics, was used.

He then applied transcendental equations to account for the thickness of the zones that receive the light charge. “These equations are those whose solutions do not use common values ​​such as additions, subtractions, divisions or multiplications, but are based on an analysis of analogies and logic to solve the unknown”, explains the physicist.

“The study of this relationship was carried out through simulations with a program developed in Python that allows the analysis of our variables in a wide range”, he mentions.

Professor Arturo Morales, from the Center for Research and Advanced Studies of the National Polytechnic Institute (IPN) of Mexico, also participated in the investigation. Its application was given for electrical semiconductors of silicon and indium phosphorus, but the developed model can be applied with any other similar compound. (Source: UNAL Agency)