Efficiency - Page 22

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.

Beijing Yaoneng Technology Co. (Auner), a Chinese developer of perovskite and crystalline silicon lamination photovoltaic technology and manufacturer of photovoltaic cells and modules, has announced that its 25cm² perovskite silicon tandem PV cell has achieved a stable conversion efficiency of 30.83% in the laboratory, which has reportedly been confirmed by China’s National Institute of Metrology.

Auner said this is a further increase by 1.26% from the 29.57% certified record achieved in February 2023 for its perovskite-silicon tandem PV cells. In addition, Auner says its large size perovskite cells are closer to meeting the mass production needs of the PV industry.

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 East China University of Science and Technology, Jilin University, Huazhong University of Science and Technology, ShanghaiTech University, Chinese Academy of Sciences, Shanghai Jiao Tong University and University of Potsdam have found that a new molecular hole-transporter can improve the performance of inverted perovskite solar cells and mini modules.

Left: mini module. Upper right: contact angle of the perovskite solution on the self assembled monolayer. Lower right: PL emission of a perovskite film. Image from University of Potsdam website.

Inverted perovskite solar cells are seen as particularly promising thanks to their simple fabrication at low costs and their relative stability. Inverted perovskite solar cells resemble organic solar cells, with a layer of perovskite replacing the organic absorber layer. In the recent study, the authors developed a novel hole transport layer based on a self-assembled monolayer. This monolayer consists of amphiphilic molecules, molecules that are both hydrophilic (water-soluble) and hydrophobic (water-fearing). 

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.

The US Department of Energy (DoE) has announced USD$52 million (EUR 47.5 million) in funding for 19 research, development and demonstration projects that seek to strengthen domestic solar manufacturing, support the recycling of solar panels and develop new solar technologies.

This funding will back several projects, among which two projects, led by the Massachusetts Institute of Technology (MIT) and the University of Colorado Boulder, will receive a total of USD$18 million through the PV Research and Development funding programme to advance perovskite solar cell devices.

Researchers from the Photovoltaics Laboratory (KPV-Lab) at King Abdullah University of Science and Technology (KAUST) have reported a perovskite/silicon tandem solar cell with a power conversion efficiency (PCE) of 33.2%—the highest tandem device efficiency in the world to date, surpassing that of Helmholtz Zentrum Berlin's (HZB) record at 32.5% PCE.

The tandem device was reportedly certified by the European Solar Test Installation (ESTI) and listed at the top of the National Renewable Energy Laboratory's (NREL), Best Research-cell Efficiency Chart.