Efficiency - Page 11

Researchers from China's Wuhan University and South China Normal University have developed a two-terminal (2T) monolithic all-perovskite tandem solar cell that uses a tin-lead (Sn-Pb) perovskite material for the top cell.

The team explained that mixed Sn-Pb perovskites have a narrow bandgap (NBG) of approximately 1.26 eV, which makes them ideal for efficient light harvesting and current-matching with wide bandgap (WBG) subcells in all-perovskite tandem cells.

Researchers at the University of Sydney, Microsolar, University of New South Wales and MiaSolé Hi-Tech Corp. have reported a monolithic perovskite–CIGS tandem solar cell on a flexible conductive steel substrate with an efficiency of 18.1%, the highest for a flexible perovskite–CIGS tandem to date, representing an important step toward flexible perovskite-based tandem photovoltaics.

The advantage of the flexible and conductive steel substrate is that the steel itself can act as both a substrate and an electrode for either large-area-monolithic-panel or smaller-area-singular single-junction or multi-junction cell fabrication.

Researchers at China's Tsinghua University, Zurich University of Applied Sciences and University of Ferrara have developed a perovskite solar cell with a new hole transport material that promises enhanced efficiency and stability while also ensuring a scalable fabrication technique.

The team explained that the new organic hole-transporting material, named T2, offers a performance advantage over conventional materials like spiro-OMeTAD as its characteristics, including unique electronic, structural, and chemical properties, synergistically enhance the efficiency of hole extraction and significantly reduce charge recombination at the interface with the perovskite layer.

High power conversion efficiency (PCE) flexible perovskite solar cells (FPSCs) are highly desired power sources for applications like aerospace and flexible electronics. However, their PCEs still lag far behind their rigid counterparts. To address this issue, researchers from Tsinghua University and National Center for Nanoscience and Technology developed a new fabrication technique that increases the efficiency of FPSCs, paving the way for use of the technology on a much larger scale. The scientists reported a high PCE flexible perovskite solar cell by controllable growth of a SnO₂ electron transport layer through constant pH chemical bath deposition (CBD). 

The team developed a new chemical bath deposition (CBD) method of depositing tin oxide (SnO₂) on a flexible substrate without requiring a strong acid, which many flexible substrates are sensitive to. The new technique allowed the researchers more control over tin oxide growth on the flexible substrate. Tin oxide serves as an electron transport layer in the FPSC, which is critical for power conversion efficiency.

Researchers from Bangladesh, Saudi Arabia, Pakistan, USA, Nepal and China have explored the fascinating structural, optical, and electronic features of calcium nitrogen iodide (Ca₃NI₃) as an attractive material for developing absorbers for efficient and reasonably priced solar cells. 

Potential applications as an absorber layer in heterostructure solar cells for the perovskite material Ca₃NI₃ have been thoroughly studied theoretically. For the Ca₃NI₃ absorber-based cell structure with CdS as the ETL layer, the best PV values were discovered using the SCAPS-1D simulator. Working temperatures, interface densities of active materials, doping densities, and layer thicknesses were all carefully considered while analyzing the PV performance. 

Researchers from the University of Science and Technology of China, Hefei National Research Center for Physical Sciences at the Microscale, Chinese Academy of Sciences and University of Colorado (CU Boulder) have reported an innovative method to manufacture perovskite solar cells. 

A major challenge in commercializing perovskite solar cells at a commercial scale is the process of coating the semiconductor onto the glass plates which are the building blocks of panels. Currently, the coating process has to take place in a small box filled with non-reactive gas, such as nitrogen, to prevent the perovskites from reacting with oxygen, which decreases their performance. “This is fine at the research stage. But when you start coating large pieces of glass, it gets harder and harder to do this in a nitrogen filled box,” said Michael McGehee, a professor in the Department of Chemical and Biological Engineering and fellow with CU Boulder’s Renewable & Sustainable Energy Institute. 

Researchers at the University of Surrey, University of Cambridge and Chinese Academy of Sciences, Xidian University, and Zhengzhou University have developed a novel approach for bifacial perovskite devices using single-walled carbon nanotubes as both front and back electrodes.

Single-walled carbon nanotubes offer high transparency, conductivity, and stability, enabling bifacial PSCs with a bifaciality factor of over 98% and a power generation density of over 36%. 

Researchers at CAS (Chinese Academy of Sciences) and Henan University have developed a nanomaterial-regulated doping strategy to pre-oxidize spiro-OMeTAD into radicals in the precursor solution with tin sulfoxide (SnSO) nanomaterials prepared at high temperature. The team increased the photoelectric conversion efficiency (PCE) of perovskite solar cells (PSCs) to 24.5% using the inorganic SnSO as a dopant to oxidize and regulate the organic hole transport layer 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9-spirobifluorene (spiro-OMeTAD).

Spiro-OMeTAD is an important hole transport layer (HTL) material. To enhance the charge transport capability of spiro-OMeTAD, lithium trifluoromethanesulfonyl imide (Li-TFSI) is required to mediate the reaction between oxygen and spiro-OMeTAD. However, this traditional doping method has low doping efficiency, and excessive Li-TFSI will remain in the spiro-OMeTAD film, leading to a decrease in the compactness and long-term conductivity of the film. The duration of the oxidation reaction usually takes 10 to 24 hours to reach the desired conductivity and work function. In this study, the researchers developed a fast and reproducible strategy to control the oxidation of the nanomaterial. They used SnSO nanomaterial to pre-oxidize spiro-OMeTAD to spiro-OMeTAD⁺TFSI^- free radicals in precursor solutions. This improved the conductivity, optimized the energy level position of HTL, and achieved a high PCE of 24.5%.

In a recent study by researchers from Henan University and the Chinese Academy of Sciences (CAS), the interface of indium tin oxide/electron transport layer (ITO/ETL) in n-i-p structured devices was targeted. Electron transport layers are typically fabricated using commercial nano tin dioxide, which often displays insufficient density. To combat this, the scientists employed the commonly used bathocuproine (BCP) material to treat the ITO/ETL interface. 

The incorporation of BCP diminishes the direct contact between the perovskite and ITO layers, while also passivating buried interface and adjusting the crystal orientation of perovskites. Furthermore, the substrate layer exhibits improved transparency, consequently elevating the utilization rate of light by perovskite.

An international collaboration between scientists from CSIRO, University of Cambridge and others has resulted in a new efficiency record for fully roll-to-roll printed solar cells.

According to the team, the cells achieved “power conversion efficiencies of up to 15.5% for individual small-area cells and 11.0% for serially-interconnected cells”.