Flexibility

Researchers from Saule Research Institute, Saule Technologies, Centre for Hybrid and Organic Solar Energy (CHOSE), CNR-SCITEC, Istituto Italiano di Tecnologia (IIT), Wroclaw University of Science and Technology, Bydgoszcz University of Science and Technology and Poznan University of Technology have demonstrated an effective strategy to improve the technical aspects of flexible perovskite solar cells,  improving the reliability and efficiency values of these devices.

The team applies large organic ammonium molecules for modifying a buried interface between a hole-transporting layer (HTL) and perovskite-absorbing material. With the 4-fluorophenethylammonium iodide (FPEAI), they achieved 18.66% efficiency for the large-area (1 cm²) flexible solar cell, a significant improvement over the pristine device without modification.

Researchers at CSIRO and Monash University have reported a flexible perovskite solar cell manufactured using roll-to-roll compatible “printing” type processes, which could potentially be used in large-scale manufacturing. To achieve this, the team developed a viable roll-to-roll process to deposit the electrode layer, which has thus far been a major challenge. The team managed to fabricated cells which achieved a maximum efficiency of 16.7%.

Photo: Hasitha Weerasinghe/CSIRO

Roll-to-roll processes signify a potential for low-cost manufacturing of flexible perovskites. However, adding the electrode layer in a process compatible with the roll-to-roll setup has proven to be a challenge. The research team in this recent work set out to address this issue and develop a process that could allow the electrode layer to be deposited without the need for solvents or heat treatments that potentially damage the perovskite layer as well.

Researchers from Sungkyunkwan University (SKKU), Korea University, Seoul National University and Korea's Frontier Energy Solution have demonstrated the feasibility of using the van der Waals stacking (vdWS) strategy to overcome the inefficiencies of flexible perovskite solar cells (f-PSCs).

The team explained that using halide perovskites can significantly increase the power conversion efficiency (PCE) of f-PSCs due to the low-temperature processability, ultrathin dimensions, low weight, and excellent optoelectronic properties of such cells. Several efforts were also made to develop the charge transporting layer (CTL), interface engineering between CTLs and perovskite, and highly-crystalline perovskite films on a flexible substrate, which further increased the f-PSC PCE to 22.44%. However, the efficiency is only 87% of the conventional glass-based PSCs. The f-PSC efficiency is affected by the physical process limitations caused by the flexible substrates' flexibility. Polymer substrates, such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET), or tin-doped indium oxide (ITO) are typically used as flexible substrates for f-PSCs.

A group of scientists, led by Prof. Yiqiang Zhan from Fudan University, has reported high-efficiency flexible perovskite solar cells (f-PSCs) by annealing a SnO₂ ETL in a rough vacuum at a low temperature (100 '), and peak efficiency reached 20.14%.

SnO₂ layers that have been prepared by this method have shown higher robustness and hydrophobicity in comparison with samples prepared in an air atmosphere and temperatures of 100 °C, leading to an improved ETL/perovskite interface connection and reducing defects in the SnO₂/perovskite interface. The appropriate density of oxygen vacancies on the surface during this treatment can be responsible for higher conductivity, which is beneficial for charge transfer.

An international team of researchers, including ones from Brown University, EPFL, Dalian University of Technology and Shaanxi Normal University, has developed a flexible thin-film perovskite solar cell with an efficiency of 21.0%.

The perovskite layer for the cell, which has an “n-i-p” layout, was fabricated using a metal-halide capping layer placed on top of a three-dimensional metal-halide perovskite film. This design reportedly provides hermetically sealed encapsulation, which is traditionally difficult to achieve in flexible perovskite cells, and also enhances the photocarrier properties at the interface between the perovskite film and the hole transport layer (HTL).

Researchers at Duke University have revealed the illusive molecular dynamics that provide halide perovskites with their desirable properties for solar energy and heat energy applications.

A key contributor to how these materials create and transport electricity reportedly stems from the way their atomic lattice twists and turns in a hinge-like fashion. The results could help materials scientists tailor the chemical recipes of these materials for a wide range of applications in an environmentally friendly way.

The U.S. Air Force recently awarded the University of Toledo (UToledo) $12.5 million to develop photovoltaic energy sheets that would live in space and harvest solar energy to transmit power wirelessly to Earth-based receivers or to other orbital or aerial instrumentation, such as communications satellites.

UToledo physicists will develop flexible solar cell sheets, each roughly the size of a piece of paper, that can be assembled and interconnected into much larger structures. The team will focus on tandem architectures and work with a variety of combinations of solar cells, perovskites included.

Scientists from South Korea have developed a foldable thin-film device with promising characteristics. Integrating a perovskite cell material and a carbon nanotube electrode, the group fabricated a device that achieved 15.2% efficiency and could be folded more than 10,000 times at a bending radius of 0.5mm.

Solar cell materials tend to be quite sensitive. Designing and manufacturing devices that can withstand the stress of being folded and bent is challenging, and many of even the most promising solutions are still quite limited in their flexibility. The scientists at Pusan National University in South Korea took a major step forward in solving this problem, fabricating a device that can be folded down to a 'bending radius' ' the minimum size of fold possible without causing damage ' of 0.5mm.

Power Roll, a developer of low-cost and lightweight flexible film for energy generation and storage, recently reported raising £3 million (around USD$4.16 million), which joins a previous raise and takes total investment in the firm to £5.8 million (over USD$8 million) over two funding rounds completed in the last six months.

Power Roll is working with a perovskite solar ink, and has already achieved 11% efficiency, with a roadmap to bring this to 20%. Power Roll also states that its substrate is compatible with any photo absorbing ink.

Solliance and U.S-based MiaSolé announced a new record - power conversion efficiency of 26.5% on a tandem solar cell that combined a top rigid semi-transparent perovskite solar cell with a bottom flexible copper indium gallium selenide (CIGS) cell.

This impressive efficiency was achieved by optimizing the bandgap and the efficiency of both the rigid semi-transparent perovskite top cell and the flexible CIGS bottom cell. The CIGS was roll to roll produced on steel foil, with a power conversion efficiency of 20.0%.