Tech Insights

Doubling Up: Perovskite Adds Efficiency to Silicon Solar Cells

April 25, 2024 by Jake Hertz

Researchers have reviewed the potential and challenges of combining and scaling silicon solar cells with perovskite. 

Photovoltaics (PV) are anticipated to be pivotal in mitigating the impending adverse impacts of climate change. They are already popular due to their cost-effectiveness, technological progress, and the ample availability of solar energy. Although crystalline silicon (c-Si) solar cells have been the primary choice for practical applications, this technology is nearing its efficiency thresholds. 

King Abdullah University of Science and Technology (KAUST) researchers explored the prospects of scaling silicon and perovskite-based solar cells. This article reviews the need to innovate PV technology and explores what the KAUST research brings to the table.

 

KAUST researcher with perovskite-based tandem solar cells

KAUST researcher with perovskite-based tandem solar cells. Image used courtesy of KAUST

 

Silicon-Based Solar Cells

Parameters like open-circuit voltage (Voc), short-circuit current (Isc), and fill factor (FF) govern the performance of silicon solar cells

Voc represents the maximum voltage available from the cell in illuminated conditions, typically around 0.6 to 0.7 volts, whereas Isc denotes the maximum current generated under short-circuit conditions. A corollary to this is the bandgap voltage, which refers to the minimum energy required to stimulate an electron to the conduction band from the valence, which is crucial for determining the cell's absorption spectrum and efficiency.

Silicon-based solar currently dominates the PV market due to its optimal bandgap, abundance, and established technology. A sub-type of silicon solar cells is the c-Si solar cells, which boast a relatively impressive efficiency limit of around 29%. 

 

Anatomy of a crystalline silicon solar panel.

Anatomy of a crystalline silicon solar panel. Image used courtesy of Massachusetts Institute of Technology

 

One challenge facing c-Si is the material experiences significant electrical losses primarily due to recombination losses and resistive effects. Recombination occurs when charge carriers recombine prematurely, while resistive losses arise from internal resistance within the cell. These factors diminish the cell's efficiency by dissipating energy as heat and impeding current flow.

 

Tandem Solar Cells 

Researchers have explored the potential of tandem solar cells combining perovskites with silicon. This effort was motivated by the desire to maximize sunlight utilization and minimize energy losses.

In recent years, the amalgam of perovskite materials with traditional silicon solar cells has boosted research in solar technology. Perovskites offer a promising avenue for enhancing solar cells’ efficiency thanks to their higher absorption coefficient and high defect tolerance. By combining silicon solar with perovskite materials in a single cell, tandem cells have the potential to improve sunlight utilization through minimized losses.

The study found perovskite/silicon tandem cells attained certified power conversion efficiencies, surpassing 33% for laboratory-scale devices. This exceeds the theoretical limit of any single-junction cell technology. With proven high-efficiency potential, minimized losses, and opportunities for further improvements, perovskite/silicon tandems are now advancing toward commercialization.

 

Efficiency comparison of both technologies.

Efficiency comparison of both technologies. Image used courtesy of Andreani et al.

 

While perovskites can be deposited at low temperatures on various surfaces, including flexible ones, challenges persist in scaling up this technology for commercial production. The most efficient lab devices have employed spin coating of a perovskite-precursor ink with anti-solvent treatment. Yet, this method is considered unsuitable for commercial processing due to scalability challenges and material wastage. Moreover, issues such as the topography of the silicon surface affecting perovskite deposition and the degradation of perovskite sub-cells due to moisture, heat, and light exposure require attention.

The study discusses alternative deposition methods, such as slot-die coating and physical vapor deposition, which are being explored to overcome scalability issues. 

 

Challenges and Opportunities Ahead

As renewable energy continues to evolve, the advancement of perovskite/silicon tandem cells could have big potential for harnessing solar energy more effectively and sustainably. Still, despite significant progress and the introduction of proof-of-concept tandem modules, the timeline for commercialization remains uncertain. Nonetheless, developing efficient tandem solar cells holds immense promise for meeting the growing energy demand while minimizing environmental impact.