Stability - Page 11

Researchers from North Carolina State University, National Synchrotron Light Source II at Brookhaven National Laboratory and Rey Juan Carlos University have created a novel materials acceleration platform (MAP), essentially a robot capable of conducting experiments more efficiently and sustainably to develop a range of new semiconductor materials with desirable attributes. The researchers have demonstrated that the new technology, called RoboMapper, can rapidly identify new perovskite materials with favorable properties and improved potential for creating stable and efficient solar cells.

“RoboMapper allows us to conduct materials testing more quickly, while also reducing both cost and energy overhead – making the entire process more sustainable,” says Aram Amassian, corresponding author of a paper on the work and a professor of materials science and engineering at North Carolina State University.

Researchers from the University of Toronto, the University of Kentucky, EPFL, North Carolina State University and Northwestern University have designed a perovskite solar cell that can stand up to high temperatures for more than 1,500 hours — an important achievement on the to commercialization. 

“Perovskite solar cells offer new pathways to overcome some of the efficiency limitations of silicon-based technology, which is the industrial standard today,” said Ted Sargent, professor of electrical and computer engineering at the McCormick School of Engineering, professor of chemistry in the Weinberg College of Arts and Sciences, and a former professor at the University of Toronto. “But due to its multi-decade head start, silicon still has an advantage in some areas, including stability. This study shows how we can close that gap.”

A team of researchers at the National Centre for Photovoltaic Research and Education (NCPRE) at the Indian Institute of Technology Bombay (IITB) has fabricated a semi-transparent perovskite solar cell (PSC) that, by combining it with a silicon-based solar cell, has demonstrated an efficiency of more than 26% for such a cell.

The team at IIT Bombay has addressed the stability issue by combining their PSC with a silicon solar cell in a tandem configuration. Combining the two different types of solar cells allows the device to convert more of the light falling on it into electricity. Apart from the higher efficiency, the tandem architecture also provides greater stability to the device, while driving its overall lifetime costs low.

Researchers from Purdue University, University of California and the University of Kentucky have constructed a new perovskite interlayer that reportedly exhibits both superior thermal and moisture stability in ambient conditions.

“Enhancing the stability and lifetime of perovskite devices is necessary in order to realize the goal of commercialization for perovskite photovoltaics,” said Jiaonan Sun. “Today, the stability of commonly used hole transporting layers (HTL) is still a bottleneck for achieving the required lifetime". Poly(triaryl amine) (PTAA) is a promising polymeric hole transporting material used in PSC applications, however, it’s hydrophobicity causes problematic interfacial contact with perovskite, limiting the device’s performance. Led by Dr. Letian Dou, the researchers successfully constructed a uniform two-dimensional (2D) perovskite interlayer with conjugated ligands, between three-dimensional (3D) perovskites and PTAA to improve the power conversion efficiency and the interfacial adhesion of the devices. These increased-ion migration, energy barrier conformal, 2D coated unencapsulated devices with new ligands provide greater thermal and moisture stability in different environments.

A Department of Energy (DoE) project, lead by University of Michigan's Prof. Zetian Mi, is using perovskites to develop high efficiency, low cost, and ultrastable production of green hydrogen fuels directly from sunlight and water.

The new method to achieve clean hydrogen through solar water splitting offers a promising path to achieving net-zero carbon emissions. The University of Michigan research team aims to stabilize perovskite-based solar cells to produce highly-efficient, low-cost, ultrastable green hydrogen fuel.

Researchers from China's Fudan University, Central South University, East China Normal University, Chinese Academy of Sciences and Suzhou University of Science and Technology, along with Canada's University of Victoria and Austria's University of Vienna, have proposed a novel strategy to achieve efficient and stable perovskite solar cells (PSCs) through introducing bis-diazirine molecules to immobilize the organic cations by covalent bonds.

The resulting PSCs exhibited a high certified efficiency of over 24% with long operational stability of over 1,000 hours. The scientists believe that this strategy also possesses great potential in other perovskite-based optoelectronic devices. 

US space agency NASA has revealed the results of an experiment it conducted to assess the performance and durability of perovskite solar cells on the International Space Station. The surprising discovery was that perovskite solar cells tested in space exhibit less degradation than reference devices tested on Earth. The specific factors in the space environment that contributed to the superior performance of the perovskite absorber film currently remain unknown.

NASA tested a perovskite absorber over a 10-month period in order to assess its resistance to vacuum, extreme temperatures, radiation, and light stressors simultaneously.

Researchers from the University of North Carolina at Chapel Hill have reported bifacial minimodules with front efficiency comparable to opaque monofacial counterparts, while gaining additional energy from albedo light. Their new design strategy could help to improve the efficiency and stability of bifacial perovskite solar cells. 

The scientists added a hydrophobic additive to the hole transport layer to protect the perovskite films from moisture. They also integrated silica nanoparticles with proper size and spacing in perovskite films to recover the absorption loss induced by the absence of reflective metal electrodes. The small-area single-junction bifacial perovskite cells achieved a power-generation density of 26.4 mW cm⁻² under 1 sun illumination and an albedo of 0.2. The bifacial minimodules showed front efficiency of over 20% and bifaciality of 74.3% and thus a power-generation density of over 23 mW cm⁻² at an albedo of 0.2. The bifacial minimodule retained 97% of its initial efficiency after light soaking under 1 sun for over 6,000 hours at 60 ± 5 °C.

A research team from City University of Hong Kong (CityU) and University of Washington recently developed a multifunctional and non-volatile additive which can improve the efficiency and stability of perovskite solar cells (PSCs) by modulating perovskite film growth. 

The team explained that the additive can be used to modulate the kinetics of perovskite film growth through a hydrogen-bond-bridged intermediate phase. The additive enables the formation of large perovskite grains and coherent grain growth from bottom to the surface of the film. The enhanced film morphology reportedly results in significantly reduced non-radiative recombinations, thus boosting the power conversion efficiency of inverted (p–i–n) solar cells to 24.8% (24.5% certified) with a low energy loss of 0.36 eV. The unencapsulated devices exhibited improved thermal stability with a T98 lifetime beyond 1,000 h under continuous heating at 65 ± 5 °C in a nitrogen-filled glovebox. This effective approach can also be applied to wide-bandgap perovskites and large-area devices to show reduced voltage loss and high efficiency.

Researchers from China's Chongqing University, the Chinese Academy of Sciences (CAS) and JA Solar Holdings Co., along with South Korea's Ulsan National Institute of Science and Technology (UNIST) and Germany's CTF Solar and have designed a perovskite solar cell based on a binary mixed hole transport layer (HTL) that reportedly offers better performance than HTLs that rely on commonly utilized hygroscopic dopants.

The team mixed two popular hole transport materials to form a binary mixed HTL, that exhibited improved moisture resistance. As a result, PSCs equipped with the mixed HTL achieved a champion power conversion efficiency (PCE) of up to 24.3% and superior operational stability. The cells without encapsulation can maintain 90% initial efficiency after storage in dark ambient conditions (30% RH) for 1200 hours. These results suggest that such a mixed HTL could be a promising strategy to meet the future photovoltaic applications demands with low-cost as well as excellent efficiency and device stability.