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  • Open Access

The Reemergence of Selenium Solar Cells

Rasmus S. Nielsen*

  • *Contact author: raniel@dtu.dk
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PRX Energy 5, 037001 – Published 1 July, 2026

DOI: https://doi.org/10.1103/fj44-cfgl

Abstract

Selenium, the world’s oldest photovoltaic material, has experienced a renaissance in research over the past decade, with certified solar cell efficiencies climbing from the historical record of 5% to breaking the 10% barrier. Its wide bandgap makes it a particularly interesting candidate for tandem solar cells and indoor photovoltaic applications, yet despite steadily improving the carrier collection, devices consistently suffer from a substantial open-circuit voltage deficit. This review provides a critical analysis of the material properties and optoelectronic quality of state-of-the-art selenium thin films. Published results from independent groups are digitized and directly compared, collectively painting a comprehensive picture of the carrier dynamics, supported and contextualized by drift-diffusion simulations. Strategies for synthesizing and processing selenium thin films are also examined in detail, highlighting not only best practices but also the underlying crystal growth kinetics that ultimately govern material quality. Finally, a series of open questions and challenges is presented, spanning from fundamental materials science and atomic-scale defect physics to device-level engineering, providing a roadmap to unlock the intrinsic photovoltaic potential of selenium and guide the future development of higher-efficiency selenium solar cells.

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Popular Summary

Selenium was the first light-absorbing material ever used in a solar cell, but it has been largely overlooked since the rise of silicon photovoltaics. Recently, however, selenium has regained attention as a promising wide bandgap semiconductor for tandem and indoor solar cells. Over the past decade, the record efficiency for selenium solar cells has more than doubled, now exceeding 10%. This Review examines what has enabled this progress and what still limits device performance. By comparing published results from research groups around the world and complementing experiments with device simulations, the Review paints a comprehensive picture of charge-carrier behavior in selenium thin films and how synthesis and processing conditions influence material quality. The analysis reveals that poor carrier lifetimes still limit device efficiency and outlines the key scientific and engineering challenges that must be solved for selenium to succeed as the optoelectronic material of tomorrow.

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PRX Energy 5, 037001– Published 1 July, 2026
  • Received 12 April 2026
  • Accepted 26 May 2026
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