Efficiency

The majority of monolithic perovskite/Si tandem solar cells (TSCs) have been built on heterojunction (HJT) Si solar cells, which have seen limited industrial uptake due to manufacturing cost and concern over the viability of metal electrodes and transparent conductive oxides (TCOs) incorporating expensive elements. Recently, researchers from The Australian National University, University of Melbourne and University of New South Wales demonstrated that high efficiencies of perovskite/Si TSCs can be achieved with Si bottom cells based on a double-side poly-Si/Si dioxide (SiO₂) passivating contact (poly-Si cell) without silver or transparent conductive oxides (TCOs), fabricated using mass-production techniques. 

In addition, a novel low-absorption, dopant-free bilayer-structured hole transport layer (HTL) composed of ultra-thin poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine (Poly-TPD) and 2,2′,7,7′-tetra(N,N-di-p-tolyl)amino-9,9-spirobifluorene (Spiro-TTB) double layers was developed for the perovskite top cell, which passivates the perovskite surface and enhances the near-interface conductivity, thus increasing the open-circuit voltage and fill factor. 

Researchers at Hong Kong Baptist University, The Hong Kong University of Science and Technology (HKUST) and Yale University have revealed the existence of surface concavities on individual crystal grains that are the fundamental blocks of perovskite thin films, and examined their significant effects on the film properties and reliability. 

Based on this discovery, the team designed a new way of making perovskite solar cells (PSCs) more efficient and stable via a chemo-elimination of these grain surface concavities.

Singapore-based startup Singfilm Solar has announced it achieved a power conversion efficiency of 22.6% for a p-i-n structure perovskite solar panel. The result was said to be confirmed by China's National PV Industry Measurement and Testing Center (NPVM). 

The design of the mini modules includes eight sub-cells connected in series on a 55 mm × 55 mm substrate, each sub-cell with a width of 5.6 mm. Each sub-cell within the module reportedly demonstrates impressive performance metrics with an open-circuit voltage of 1.169 V, a short-circuit current of 25 mA/cm², and a fill factor of 77.4%.

Researchers from Peking University, Tsinghua University, Beijing Institute of Technology and Ecole Polytechnique Fédérale de Lausanne (EPFL) have tackled a reproducibility challenge in black-phase formamidinium lead iodide (α-FAPbI₃) perovskites. They explained that while this is the desired phase for photovoltaic applications, water can trigger formation of photoinactive impurity phases such as δ-FAPbI₃. The team found that the classic solvent system for perovskite fabrication exacerbates this reproducibility issue. 

Growth of the photoactive black phase of formamidinium lead iodide (α-FAPbI₃) usually requires dimethyl sulfoxide solvent, but the hygroscopic nature of this chemical also promotes water-induced degradation to the photoinactive phase. the scientists showed that a larger chlorinated organic molecule can form a hydrophobic capping layer that enables perovskite crystallization under humid conditions by protecting growing crystallites from water. 

A team of researchers, led by the Fudan University in China, has developed a p-i-n structure inverted perovskite solar cell that uses a synergistic bimolecular interlayer (SBI) and achieves what the team says is the smallest nonradiative recombination induced open-circuit voltage loss ever reported. 

Schematic illustration of p-i-n PSC using MPA/PEAI as SBI. Image from Nature Communications

The researchers' SBI strategy consisted of depositing 4-methoxyphenylphosphonic acid (MPA) and 2-phenylethylammonium iodide (PEAI) as modulators to functionalize the perovskite surface.

Researchers at India's Chitkara University Institute of Engineering and Technology have developed 2D perovskite solar cells with MXene materials to build a PV device with remarkable efficiency and open-circuit voltage. The scientists claim the new cell architecture can help charge carriers move smoothly through the cell layers and reduce recombination losses.

The team's 2D DJ perovskite solar cell implemented bandgap grading techniques and use contacts based on a functionalized two-dimensional titanium carbide known as MXene. MXenes are compounds that take their name from their graphene-like morphology and are made via selective etching of certain atomic layers from a bulk crystal known as MAX. Recently, MXenes materials have shown promise for use in PV technology due to their unique optoelectronic properties, such as their large charge carrier mobility, excellent metallic conductivity, high optical transmittance, and tunable work function (WF).

Researchers from China's Zhejiang University, Westlake University, Southern University of Science and Technology, Chinese Academy of Sciences (CAS) and University of California Los Angeles in the U.S have reported a family of high-entropy organic–inorganic hybrid perovskites for photovoltaic applications.  

The scientists built, for the first time, an inverted perovskite solar cell relying on a high-entropy hybrid perovskite material. The result is a device with an improved open-circuit voltage and fill factor, due to reduced non-radiative recombinations and optimized interface.

Researchers from Zhejiang University of Technology and King Abdullah University of Science and Technology (KAUST) have utilized two sulfone-based organic molecules known as diphenylsulfone (DPS) and 4,4′-dimethyldiphenylsulfone (DMPS) to passivate absorber defects in perovskite solar cells and improve their performance. As a result, the team reported a device with a higher electron cloud density at the interface between the perovskite material and the passivation layer.

The scientists used the molecules to improve charge distribution at the interface between the cell's perovskite absorber and the passivation layer, which reportedly creates electron-rich systems on the surface of perovskite. Using density functional theory (DFT) to compute a wide variety of properties of almost any kind of atomic system, they simulated the charge density distributions of the interactions of DPS and DMPS with formamidinium lead iodide (FAPbI₃) perovskite material.

Researchers from King Abdullah University of Science and Technology (KAUST) have reported four-terminal perovskite/perovskite/silicon triple-junction tandem solar cells, with the device structure comprising a perovskite single-junction top cell and monolithic perovskite/silicon tandem bottom cell.

The cells reportedly yielded a 31.5% power conversion efficiency, which the team said is the highest efficiency ever reported for perovskite-based 4-T and triple-junction tandem solar cells. The key feature of the cell is the hole transport layer of the top perovskite cell, which was engineered with self-assembled monolayers.

Researchers from Colombia's Universidad de los Andes recently set out to develop inverted perovskite solar cells (IPSCs) with a hole transport layer based on indium-doped nickel oxide. The result is a champion device that achieved an efficiency of 20.06% with remarkable stability.

The team explained that NiOx has an energy gap of over 3.5 eV, exceptional chemical stability, durability, low toxicity, and cost-effective processing. The scientists said that in the case of NiOx-based inverted perovskite solar cells, the doping approach has indeed paved the way for HTL optimization, frequently through observable improvements also at the interface level and in the perovskite layer.