EPFL is a Switzerland-based technical university and research center. EPFL is focused on three missions: teaching, research and technology transfer.
EPFL works together with an extensive network of partners including other universities and institutes of technology, secondary schools and colleges, industry and economy, political circles and the general public.
EPFL does extensive perovskite R&D work and is responsible for many publications and advancements in the field.
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New type of hole-selective molecular contact enables inverted perovskite solar cell with >26% efficiency
Researchers from China's Xi’an Jiaotong University, Huazhong University of Science and Technology, Fudan University, ULVAC-PHI Instruments, National University of Singapore (NUS), Sweden's Uppsala University and EPFL have developed a self-assembled bilayer (SAB) that can be used as a hole contact material that grants improved adhesive contact with the perovskite film.
A schematic illustration of the inverted PSCs. Image from: Nature Energy
The team went on to fabricate an inverted perovskite solar cell that utilizes the self-assembled bilayer (SAB) as a hole-selective molecular contact. The cell was made with a substrate made of glass and transparent conductive oxides (TCOs), the proposed bilayer, the perovskite absorber, an ETL based on buckminsterfullerene (C60), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact.
Researchers fabricate bifacial perovskite/silicon heterojunction tandem solar cells based on FAPbI3-based perovskite via hybrid evaporation-spin coating
Researchers from EPFL and CSEM recently fabricated efficient (>20 %) and stable (T80 ∼ 720 h) planar FAPbI3-based perovskite (1.54 eV) solar cells via a hybrid evaporation-spin coating process.
FAPbI3-based perovskite films were fabricated via a hybrid two-step evaporation-spin coating method in an inverted (p-i-n) configuration, and the effects of optimized parameters on the film growth and devices’ performances were investigated. Transferring these films into tandem devices atop single-side textured silicon heterojunction bottom cells, the team obtained an efficiency of >24 % under AM1.5 G illumination for monofacial devices with an active area of 1.21 cm2. Furthermore, the bifacial devices generated >27 mW cm−2 power output with 15 % rear illumination fraction.
Wide-bandgap perovskite films with improved crystal orientation enable all-perovskite tandem solar cells with >29% efficiency
Monolithic all-perovskite tandem solar cells present a promising approach for exceeding the efficiency limit of single-junction solar cells. However, the substantial open-circuit voltage loss in the wide-bandgap perovskite subcell hinders further improvements in power-conversion efficiency. Now, researchers from China's Nanjing University, Renshine Solar (Suzhou) and Ecole Polytechnique Fédérale de Lausanne (EPFL) have developed wide-bandgap perovskite films with improved crystal orientation that suppress non-radiative recombination.
The team showed that using two-dimensional perovskite as an intermediate phase on the film surface promotes heterogeneous nucleation along the three-dimensional perovskite facets during crystallization. Preferred orientations can be realized by augmenting the quantity of two-dimensional phases through surface composition engineering, without the need for excessive two-dimensional ligands that otherwise impede carrier transport.
Researchers tweak perovskite precursor solutions to produce useful cations that improve perovskite solar modules
Researchers from Ecole Polytechnique Fédérale de Lausanne (EPFL), North China Electric Power University, Westlake University, Lomonosov Moscow State University and others have described the addition of N,N-dimethylmethyleneiminium chloride ([Dmei]Cl) into perovskite precursor solutions to produce two cations in situ—namely 3-methyl-2,3,4,5-tetrahydro-1,3,5-triazin-1-ium ([MTTZ]+) and dimethylammonium ([DMA]+) cations - that enhanced the photovoltaic
performance and stability of perovskite solar modules.
A schematic of the roles of [MTTZ]+ and [DMA]+ in the 3D perovskite matrix. Image from: Science
The team explained that the in situ formation of [MTTZ]+ cation increased the formation energy of iodine vacancies and enhanced the migration energy barrier of iodide and cesium ions, which suppressed nonradiative recombination, thermal decomposition, and phase segregation processes.
Researchers develop optimization strategies that may pave the way towards industry-compatible, highly efficient tandem cells based on a production-compatible SHJ bottom cell
Researchers from Helmholtz Zentrum Berlin (HZB) and École Polytechnique Fédérale de Lausanne (EPFL) have presented optimization strategies for top cell processing and integration into silicon heterojunction (SHJ) bottom cells based on industrial Czochralski (Cz)-Si wafers of 140 μm thickness.
Schematic illustration of the perovskite/silicon tandem solar cell based on 140 μm Cz-Si. Image credit: ACS Applied Materials & Interfaces
The team showed that combining the self-assembled monolayer [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with an additional phosphonic acid (PA) with different functional groups, can improve film formation when used as a hole transport layer improving wettability, minimizing shunt fraction and reducing nonradiative losses at the buried interface.
