This short communication highlights our latest results towards high-efficiency microcrystalline silicon single-junction solar cells. By combining adequate cell design with high-quality material, a new world record efficiency was achieved for single-junction microcrystalline silicon solar cell, with a conversion efficiency of 10.69%, independently confirmed at ISE CalLab PV Cells. Such significant conversion efficiency could be achieved with only 1.8 mm of Si.

We develop a Maxwell-Schrödinger formalism in order to describe the radiative interaction mechanism between semiconductor quantum dots. We solve the Maxwell equations for the electromagnetic field coupled to the polarization field of a quantum dot ensemble through a linear non-local susceptibility and compute the polariton resonances of the system. The radiative coupling, mediated by both radiative and surface photon modes, causes the emergence of collective modes whose lifetimes are longer or shorter compared to the ones of non-interacting dots. The magnitude of the coupling and the collective mode energies depend on the detuning and on the mutual quantum dot distance. The spatial range of this coupling mechanism is of the order of the wavelength. This coupling should therefore be accounted for when considering quantum dots as building blocks of integrated systems for quantum information processing.

To further lower production costs and increase conversion efficiency of thin‐film silicon solar modules, challenges are the deposition of high‐quality microcrystalline silicon (μc‐Si:H) at an increased rate and on textured substrates that guarantee efficient light trapping. A qualitative model that explains how plasma processes act on the properties of μc‐Si:H and on the related solar cell performance is presented, evidencing the growth of two different material phases. The first phase, which gives signature for bulk defect density, can be obtained at high quality over a wide range of plasma process parameters and dominates cell performance on flat substrates. The second phase, which consists of nanoporous 2D regions, typically appears when the material is grown on substrates with inappropriate roughness, and alters or even dominates the electrical performance of the device. The formation of this second material phase is shown to be highly sensitive to deposition conditions and substrate geometry, especially at high deposition rates. This porous material phase is more prone to the incorporation of contaminants present in the plasma during film deposition and is reported to lead to solar cells with instabilities with respect to humidity exposure and post‐deposition oxidation. It is demonstrated how defective zones influence can be mitigated by the choice of suitable plasma processes and silicon sub‐oxide doped layers, for reaching high efficiency stable thin film silicon solar cells.

Doped layers made of nanostructured silicon phases embedded in a silicon oxide matrix were implemented in thin film silicon solar cells. Their combination with optimized deposition processes for the silicon intrinsic layers is shown to allow for an increased resilience of the cell design to the substrate texture, with high electrical properties conserved on rough substrates. The presented optimizations thus permit turning the efficient light trapping provided by highly textured front electrodes into increased cell efficiencies, as reported for single junction cells and for amorphous silicon (a‐Si)/microcrystalline silicon tandem cells. Initial and stabilized efficiencies of 12.7 and 11.3%, respectively, are reported for such tandem configuration implementing a 1.1 µm thick microcrystalline silicon bottom cell. SEM image after FIB cut of an amorphous silicon/microcrystalline silicon tandem cell reported with a stabilized efficiency of 11.3% for a bottom cell thickness of about 1.1 µm.

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