Transparency

The fabrication of perovskite/Si tandem solar cells often encounters the challenge of selecting a suitable sputtering buffer layer (SBL) to prevent damage during the transparent electrode deposition. In their recent work, researchers from China's Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU), Chinese Academy of Sciences and Ningbo New Materials Testing and Evaluation Center Co. developed a perovskite-silicon tandem solar cell that uses an indium oxide sputtering buffer layer to protect the perovskite absorber and the electron transport layer from damages that might occur during the electrode deposition process. The new layer not only granted this protection but also showed strong optical and electrical properties. 

The team introduced the indium oxide (In₂O₃) buffer layer via e-beam deposition to fabricate semi-transparent perovskite solar cells. The optical transmittance and electrical conductivity of In₂O₃ highly depend on the deposition rate. High deposition rate results in high ratio of metallic indium in the film, which causes severe parasitic absorption. A 20 nm-thick In₂O₃ film deposited at lower rate demonstrated high conductivity, transmittance and robust protection during sputtering. 

Semi-transparent solar cells are appealing for many different applications such as building-integrated photovoltaics (BIPVs), tandem solar cells and in wearable electronics. Perovskites could be ideal for semi-transparent applications as they are versatile and easy to optimize.

Semi-transparent perovskite solar cells (ST-PSCs) must try to maximize efficiency and transparency. Methods such as bandgap engineering, thinning perovskite layers, and creating discontinuous structures are being developed to improve their performance. However, challenges still remain with ST-PSC development, such as phase stability and defect management.

An EU-funded Laperitivo project was launched earlier this month, focused on manufacturing large-area stable perovskite solar modules. Laperitivo stands for “large-area perovskite solar module manufacturing with high efficiency, long-term stability, and low environmental impact.” The project aims to achieve 22% efficiency for 900 cm² opaque panels and 20% for semi-transparent modules with more than 95% bifaciality.

The team will focus, among other things, on solving scalability challenges, to promote large-scale mass production with minimized losses. The abstract of the project’s EU funding paper also states that: “Indoor and outdoor field tests will be performed to monitor module reliability. Safety, circularity, and sustainability will be assessed to demonstrate products with minimized environmental impact.”

Reports suggest that a solar power project in China, which utilizes translucent perovskite panels, has recently been connected to the grid in Gansu Province. This project was developed through a collaboration between the Electric Power Science Research Institute of the China State Grid Gansu Electric Power Company and a renewable energy subsidiary of China Datang Corp.

It was stated that the perovskite solar cells were processed to be translucent by the application of special graphical structures, including grind lines and dots, on the perovskite film. The specific structures are the result of precise control of parameters, including exposure time and depth. The graphical structures allow for the optimization of the light propagation path within the cell, thereby enhancing light absorption efficiency and improving the cell’s photoelectric conversion performance.

Researchers from Austria's Johannes Kepler University Linz have developed lightweight, thin (<2.5 μm), flexible and transparent-conductive-oxide-free quasi 2D perovskite solar cells by incorporating alpha-methylbenzyl ammonium iodide into the photoactive perovskite layer. 

The team fabricated the devices directly on an ultrathin polymer foil coated with an alumina barrier layer to ensure environmental and mechanical stability without compromising weight and flexibility.

Researchers from the University of Stuttgart, Forschungszentrum Jülich, Brandenburg University of Technology Cottbus-Senftenberg and University of Victoria have reported 'the highest open-circuit voltage recorded to date' for a single-junction perovskite solar cell based on hybrid methylamine lead chloride (MAPbCl₃). The novel perovskite absorber was fabricated with a two-step deposition method and annealing under molecular nitrogen (N₂) gas inside a glovebox.

Image from: ACS Publications

The team fabricated a single-junction transparent perovskite solar cell based on hybrid methylamine lead chloride (MAPbCl₃), a perovskite material with one of the highest energy bandgaps among all perovskites. The team stated that this new cell could open the door for wide bandgap perovskites solar cells, which will be important not just for applications like Internet-of-Things (IoT) or solar windows, but also multijunction solar cells. The new work is especially noteworthy as single junction perovskites with wide bandgaps have not yet reached high voltages before.

Researchers from the Korea Institute of Energy Research (KIER), Korea Research Institute of Standards and Science, Jusung Engineering and the Jülich Research Center have reported an advancement in the stability and efficiency of semi-transparent perovskite solar cells.

The semi-transparent solar cells achieved an impressive efficiency of 21.68%, which is said to be the highest efficiency to date among perovskite solar cells that use transparent electrodes. Additionally, they showed remarkable durability, with over 99% of their initial efficiency maintained after 240 hours of operation.

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.

Scientists from Karlsruhe Institute of Technology (KIT) have developed a new way to fabricate micro-patterned translucent perovskite solar cells that could be used in tandem solar modules intended for applications in building-integrated photovoltaics (BIPV). “While translucent perovskite multi-junction devices have been envisaged and recognized as a promising path towards high- efficiency neutral-color transparent PV, the tolerance of complex perovskite tandem stacks against extensive laser scribing has yet to be explored,” the research group said.

The researchers noted that the cells have thus far provided decent levels of power conversion efficiency while maintaining a high average visible transmittance (AVT). They used a custom-built laser scribing setup to fabricate a perovskite solar cell with n–i–p architecture and with an active area of 0.105 cm². The device is based on an indium tin oxide (ITO) substrate, a hole transport layer made of carbazole (2PACz), an electron transport layer made of buckminsterfullerene (C60), an absorber based on methylammonium lead triiodide (CH3NH3PbI3), a bathocuproine (BCP) buffer layer, and a gold (Au) metal contact.

The Indian Institute of Technology Roorkee (IIT Roorkee) and General Insurance Corporation of India (GIC Re) have signed a partnership agreement to develop perovskite-based solar window technology that will enhance the solar power generation in India and lead to greater sustainable development.

The new solar window technology will be designed and developed by Prof. Soumitra Satapathi from the Department of Physics (IIT Roorkee) and his team. Under the program, semi-transparent perovskite solar cells will be developed for building integrated photovoltaics (BIPV). The new window solar technology will harness electricity during the daytime and reduce reliance on traditional electricity sources.