Efficiency

It was reported that on May 24, at the 16th (2023) International Solar Photovoltaic and Smart Energy (Shanghai) Exhibition (SNEC), LONGi Green Energy Technology announced its “STAR Innovative Ecological Cooperation Platform” and its newly achieved efficiency of 31.8% for perovskite/crystalline silicon tandem solar cells based on commercial CZ silicon wafers.

The German Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) reportedly certified LONGi's conversion efficiency of 31.8% for perovskite/crystalline silicon tandem solar cells based on commercial CZ silicon wafers. This was said to be the highest internationally certified conversion efficiency based on the superposition of perovskite on commercial CZ silicon wafers.

Less than two months after achieving a new world record for tandem solar cell efficiency of 33.2%, KAUST researchers have announced an improvement to this number by reaching a power conversion efficiency of 33.7% for a perovskite-silicon solar cell. 

The result was reportedly certified by the European Solar Test Installation (ESTI).

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. 

Researchers from the University of North Carolina at Chapel Hill, University of Toledo and Perotech Energy have found that bathocuproine, which is often used as an electron-transport material, can improve power-conversion efficiency and stability when added to the hole-transport layer. 

The chelation product of bathocuproine with lead ions is insoluble in the perovskite ink and also decreases the formation of amorphous regions by reducing the amount of trapped dimethyl sulfoxide solvent. Minimodules with an aperture area of 26.9 square centimeters had a certified efficiency of 21.8% and light-soaking stability exceeding 2000 hours. 

Oxford PV has announced 'a new world record for the efficiency of a commercial-sized solar cell'. The efficiency record was achieved on a commercial-sized ‘M4’ (258.15 cm²) solar cell. The cell is a 2T device made by depositing a perovskite thin-film cell onto a conventional silicon heterojunction cell.

The record-breaking solar cell converted 28.6% of the sun’s energy into electricity, as independently certified by Fraunhofer ISE. The solar cell was produced at Oxford PV’s integrated production line in Brandenburg an der Havel, Germany. The factory has commenced initial production of the company’s tandem solar cells for integration by solar module manufacturing partners and is ramping up to higher volumes. The site, operational since 2017, houses the world’s first volume manufacturing line for perovskite-on-silicon tandem solar cells.

To pave the way for the industrial implementation of efficient perovskite-silicon PV modules, a reliable measuring system for tandem solar cells and modules must be established. Only then can objective comparisons between different cells and modules take place. In contrast to conventional silicon PV modules, however, the calibration is considerably more challenging. 

A project consortium, led by the Fraunhofer Institute for Solar Energy Systems ISE, is therefore developing methods for characterizing perovskite-based tandem modules in the "Katana" project, funded by the German Federal Ministry for Economic Affairs and Climate BMWK. The solar simulator specially built for this purpose by the company Wavelabs Solar Metrology Systems GmbH is now in use in the CalLab PV Modules of the research institute.

Researchers from Solliance partners Delft University of Technology, Eindhoven University of Technology and TNO have developed a tandem perovskite-silicon solar cell using a new approach to interface engineering. 

The team's findings demonstrate the potential of using (n)nc-SiOx:H and (n)nc-Si:H interfacial layers in tandem solar cells to minimize reflection losses at the interfaces between the perovskite and silicon sub-cells, as explained by the scientists. Through optimizing interference effects, these light management techniques can be applied to various tandem structures.

Scientists from the Nanjing University of Aeronautics and Astronautics in China and University of Okara in Pakistan have simulated a solar cell based on an absorber using a CsSnI₃ perovskite material, which is an inorganic perovskite that has low exciton binding energy, a high absorbance coefficient, and an energy bandgap of 1.3 eV.

The researchers used the SCAPS-1D solar cell capacitance software, which is a simulation tool for thin-film solar cells developed by the University of Ghent in Belgium, to simulate several cell designs with different electron transport layers (ETLs) and hole transport layers (HTLs). Through a series of simulations, the team found that the best possible cell configuration was provided by a device based on a substrate made of fluorine-doped tin oxide (FTO), a titanium oxide (TiO₂) ETL, the CsSnI₃ absorber, an HTL based on nickel(II) oxide (NiOx), and back electrodes.

Researchers from China's Henan University and Chinese Academy of Sciences (CAS) have reported an extremely efficient carbon electrode perovskite solar cell that reportedly achieves a power conversion efficiency of 20.8% while providing enhanced stability.

Schematic diagram of the fabrication process of bilayer HTL carbon electrode perovskite solar cells. Image from the study published in Journal of Materials Research and Technology

Commonly used metal contact electrodes can promote the degradation of perovskite solar cells due to the diffusion of metal impurities across the interfaces. This issue could be theoretically overcome by replacing the metal contact with carbon electrodes, which are highly promising for commercialization due to their ambient pressure processability based on industrially established printing techniques. The problem is, however,  that perovskite solar cells based on carbon electrodes lead to performance losses at the point where the carbon electrode meets the perovskite layer.

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.