NREL

Current photovoltaic (PV) panels typically contain interconnected solar cells that are vacuum laminated with a polymer encapsulant between two pieces of glass or glass with a polymer backsheet. This packaging approach is common in conventional photovoltaic technologies such as silicon and thin-film solar modules, contributing to thermal management, mechanical reinforcement, and environmental protection to enable long lifetimes. Commercial vacuum lamination processes typically occur at 150 °C to ensure cross-linking and/or glass bonding of the encapsulant to the glass and PV cells. Perovskite solar cells (PSCs) are known to degrade under thermal stresses, especially at temperatures above 100 °C.

Researchers from NREL and The Dow Chemical Company have examined degradation modes during lamination and developed internal diffusion barriers within the PSC to withstand the harsh thermal conditions of vacuum lamination. 

Researchers at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) and the Center for Hybrid Organic Inorganic Semiconductors for Energy (CHOISE), an Energy Frontier Research Center (EFRC), University of Wisconsin-Madison, University of Colorado Boulder, Duke University and University of Utah have discovered a new process to induce chirality in halide perovskite semiconductors, which could open the door to cutting-edge electronic applications.

The development is the latest in a series of advancements made by the team involving the introduction and control of chirality. Chirality refers to a structure that cannot be superimposed on its mirror image, such as a hand, and allows greater control of electrons by directing their “spin.” Most traditional optoelectronic devices in use today exploit control of charge and light but not the spin of the electron.

Researchers from City University of Hong Kong, National Renewable Energy Laboratory (NREL) and Imperial College London have improved the long-term stability of perovskite solar cells with an atomic-layer deposition (ALD) method that replaces the fullerene electron transport layer with tin oxide. 

Professor Zhu Zonglong (left) and Dr Gao Danpeng of City University of Hong Kong hold their innovative solar cells. Image credit: Eurekalert

The team started by depositing the perovskite and the hole-transporter layer in a single step. Then, they used ALD to create an oxygen-deficient tin oxide layer to reduce the band offset to a thicker, overgrown layer of normal tin oxide. Solar cells had a power conversion efficiency of more than 25%, and they retained more than 95% of efficiency after 2000 hours of maximum power point operations at 65°C. 

The U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) Small Innovative Projects in Solar (SIPS) 2024 funding program provides $5.4 million for seedling R&D projects that focus on innovative and novel ideas in photovoltaics (PV) and concentrating solar-thermal power (CSP) and are riskier than research ideas based on established technologies.

The 16 selected projects were recently announced, among them were 5 perovskite-related projects.

In contrast to conventional (n–i–p) PSCs, inverted (p–i–n) PSCs offer enhanced stability and integrability with tandem solar cell architectures, which have garnered increasing interest. However, p–i–n cells tend to suffer from energy level misalignment with transport layers, imbalanced transport of photo-generated electrons and holes, and significant defects with the perovskite films.

Recently, researchers from King Abdullah University of Science and Technology (KAUST), Newcastle University, National Renewable Energy Laboratory (NREL) and Saudi Aramco Research and Development Center developed a nonionic n-type molecule (tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB) that, through hydrogen bonding and Lewis acid–base reactions with perovskite surfaces or grain boundaries, enables in situ modulation of perovskite energetics, effectively mitigating the key challenges of p–i–n perovskite solar cells (PSCs). 

Solar cells and light-emitting diodes strive to maintain the excited state kinetics of molecules. A major loss mechanism, especially in the highest efficiency systems, is called exciton-exciton annihilation, leading to lowering of solar efficiency and of light output in LEDs. Controlling the amount of exciton-exciton annihilation is therefore an important goal that affects efficiency.

National Renewable Energy Laboratory (NREL) researchers, working with researchers from University of Colorado Boulder, sought to control exciton/exciton annihilation by coupling excitons with cavity polaritons, which are essentially photons caught between two mirrors, to combat energy dissipation and potentially increase efficiency in optoelectronic devices. As detailed in their recent article, the scientists used transient absorption spectroscopy to demonstrate control of the loss mechanism by varying the separation between the two mirrors forming the cavity enclosing the 2D perovskite (PEA)₂PbI₄ (PEPI) layer. This perovskite material is a candidate for future LED applications.

Researchers from NREL, Yale University, Hong Kong Baptist University and The Hong Kong University of Science and Technology (HKUST) have designed a chiral-structured interface in perovskite solar cells, which reportedly enhances their reliability and power conversion efficiency.

Using the PSC developed by the team to power a mobile phone as a demo. Image from Techxplore, credit HKUST

The performance of PSCs still faces significant barriers to commercialization, particularly due to various stability issues under real-world conditions. A major challenge is, according to the team, the insufficient adhesion between the different layers of the cells, resulting in limited interfacial reliability. To address this issue, the team was inspired by the mechanical strength of natural chiral materials and constructed an unprecedented chiral-structured interface in PSCs, unlocking very high reliability.

Researchers at NREL have examined how metal halide perovskite photovoltaics (MHP-PV) could scale a sustainable supply chain while appreciably contributing to a global renewable energy transition. They evaluated the critical material concerns, embodied energy, carbon impacts and circular supply chain processes of MHP-PVs. 

Perovskite-based solar panels may play an important role amid global decarbonization efforts to reduce greenhouse gas emissions. As the technology emerges from the testing stages, scientists are assessing how best to design the solar panels to minimize their impact on the environment decades from now.

Researchers at the National Renewable Energy Laboratory (NREL) and University of North Carolina at Chapel Hill have reported a systematic study on the degradation mechanisms of p–i–n structure perovskite solar cells (PSCs) under reverse bias. Reverse bias is a phenomenon that can occur when, for example, an individual cell is shaded and other cells in the module try to push a higher current through it, increasing the temperature and potential damage to the cells. These conditions make solar cells unstable and deteriorate their performance over time.

The team's new strategy could improve the stability of PSCs under reverse bias conditions and facilitate the future deployment of perovskite-based photovoltaics (PVs) in real-world settings.

Researchers from National Renewable Energy Laboratory (NREL), University of Utah, Université de Lorraine CNRS and University of Colorado Boulder have improved upon their previous work, that included incorporating a perovskite layer that allowed the creation of a new type of polarized light-emitting diode (LED) that emits spin-controlled photons at room temperature without the use of magnetic fields or ferromagnetic contacts. In their latest work, they have gone a step further by integrating a III-V semiconductor optoelectronic structure with a chiral halide perovskite semiconductor. 

The team transformed an existing commercialized LED into one that also controls the spin of electrons. The results could provide a pathway toward transforming modern optoelectronics, a field that relies on the control of light and encompasses LEDs, solar cells, and telecommunications lasers, among other devices.