Stability

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.

Researchers at Nanjing University, Nankai University, East China Normal University and University of Toronto have developed new inorganic wide-bandgap perovskite subcells that could increase the efficiency and stability of all-perovskite tandem solar cells. Their design involves the insertion of a passivating dipole layer at the interface between organic transport layers and inorganic perovskites within the cells.

The scientists explained that efficient tandem solar cells made using hybrid organic inorganic wide-bandgap perovskites have thus far maintained only 90% of their initial PCE for 600 hours of operation at their maximum power point (MPP). Therefore, achieving long-term stability has become a critical issue for the commercialization of all-perovskite tandem solar cells.

Researchers at the Indian Institute of Technology Bombay have reported NIR-transparent perovskite solar cells (PSCs) with the stable triple cation perovskite as the photo-absorber and subsequent integration with a Si solar cell in a 4T tandem device. The scientists said that the cell provides outstanding stability in the dark, as well as continuous heating conditions.

The top perovskite cell incorporates a room-temperature sputtered transparent conducting electrode (TCE) as a rear electrode. It has an n–i–p structure and utilizes an anti-reflecting coating, an electron transport layer (ETL) made of tin(IV) oxide (SnO₂), a perovskite layer, a molybdenum oxide (MoOx) layer, and a spiro-OMeTAD hole transport layer (HTL). The MoOx buffer layer protects the perovskite photo-absorber and charge transport layers from any sputter damage.

Researchers from the University of Surrey, University of Toronto, University of Stuttgart and Ulsan National Institute of Science and Technology have found that stabilizing the perovskite "photoactive phases" – the specific part of the material that is responsible for converting light energy into electrical energy – is the key step towards extending the lifespan of perovskite solar cells. The stability of the photoactive phase is important because if it degrades or breaks down over time, the solar cell will not be able to generate electricity efficiently. Therefore, stabilizing the photoactive phase is a critical step in improving the longevity and effectiveness of perovskite solar cells.

In the study, the team assessed the current understanding of these phase instabilities and summarized the approaches for stabilizing the desired phases, covering aspects from fundamental research to device engineering. The scientists subsequently analyzed the remaining challenges for perovskite PVs and demonstrated the opportunities to enhance phase stability with ongoing materials discovery and in operando analysis. Finally, the team proposed future directions towards upscaling perovskite modules, multijunction PVs and other potential applications.

An international research team that includes scientists from EPFL in Switzerland, Middle East Technical University (METU) in Turkey, Lomonosov Moscow State University in Russia and The University of Tokyo has fabricated a quasi-2D perovskite solar cell with a unique type of salt to enhance hole extraction. 

The triple-cation perovskite absorber was treated with phenethylammonium iodide (PEAI), a modulator that alters the perovskite film's surface energy and forms a quasi-2D structure without further annealing. The result is a 23.08%-efficient device that is also able to retain 95% of its initial efficiency after 900 hours.