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A multifaceted characterization approach is proposed, aiming to establish a link between nanoscale electrical properties and macroscale device characteristics. Current–voltage (I–V) measurements are combined with admittance spectroscopy (AS) and deep‐level transient spectroscopy (DLTS) for the analysis of charge‐related performance losses with time‐of‐flight secondary‐ion mass spectrometry to complete the understanding of ionic motion in the device. This is applied to the study of surface treatment in perovskite solar cells, which implements several strategies to improve band alignment, perovskite grain growth, and chemical passivation. An increase of both open‐circuit voltage (Voc) and fill factor of respectively 90 mV and 11% is shown after surface treatment, with an absolute efficiency increase of 4%. AS measurements, coupled with a lumped elements model, rule out the impact of transport layers as the origin of the performance improvement, rather pointing toward a reduction in ionic resistance in the perovskite bulk. Analysis of the DLTS response yields an activation energy of 0.41 eV, which is likely related to the same ionic mechanism discovered with AS. Finally, both of these techniques enable to show that the surface treatment main contribution is to reduce ion‐related recombination of charge carriers. [ABSTRACT FROM AUTHOR]

Lithium fluoride (LiF) is currently a very popular dielectric material used as a passivation or transport layer in a variety of applications, especially in high-efficiency solar cells. Despite this, its conduction properties and interface behavior with silicon remain largely unexplored. In this work, a LiF metal–insulator–semiconductor (MIS) structure is fabricated and characterized, and its properties are compared to the well-understood aluminum oxide (Al2O3) MIS structure. First, a higher current density in LiF compared to Al2O3 is highlighted, as well as its PN junction-like behavior with n-type silicon (n-Si), being rather unconventional for a dielectric layer. C–V measurements showcase the likely presence of an interface defect, causing an increase in the apparent doping and a shift in the flatband voltage VFB by +70 meV. This defect is found to be of the acceptor type, which renders the interface fixed charge more negative and improves the field-effect passivation in the case of a negative Qf. Finally, a density of interface states D i t ≈ 2 × 10 11 cm − 2 eV − 1 was found for LiF/n-Si, which is a low value showing appropriate chemical passivation at the interface. Overall, this work enables us to shed more light on the interface properties of LiF on n-Si, which is an essential step toward its wider use in state-of-the-art solar cells and other silicon-based devices. [ABSTRACT FROM AUTHOR]

The industrial n-type passivated emitter and rear totally diffused (PERT) cell with doped polysilicon passivating contacts is an attractive nextgeneration technology, as average efficiencies above 24% have recently been demonstrated in mass production. Despite these very promising efficiencies, several factors are limiting this technology's rapid adoption in mass production, including the relatively higher cost of manufacturing equipment and the increased process complexity, leading to lower manufacturing yields. This paper provides a short overview of historical developments, presents the main approaches in mass production today, discusses potential process simplifications, and briefly touches upon a key topic for the future, namely reducing the silver (Ag) consumption per cell. [ABSTRACT FROM AUTHOR]

The studies of porous silicon as a one-dimensional photonic crystal have led to solutions allowing the fabrication of broad photonic band gaps as large as several hundreds nanometers for various types of applications. In this work we demonstrate the use of the chirping process, i.e., the gradual increase in the spatial period of the structure, as it is used in image processing, to design porous silicon broad-band reflectors for thin-film silicon solar cells. Modeling of those layers is done using linear design method and a simulation software. Such chirped structures are fabricated by an anodization process. Samples are prepared on mono and multicrystalline silicon substrates with 15, 40, 60, and 80 layers. The reflectance spectra of such prepared porous reflectors are evaluated and the results show an increase in bandwidth of over 50% of the total width in comparison with the conventional, unchirped reflectors. We demonstrate clear advantages of introducing chirped multilayer structures over conventional ones. Although some understanding of chirping exists mainly in the field of image processing and photonics, detailed study of chirped porous structures as broad-band reflectors is needed for their implementation in thin-film epitaxial silicon solar cells. A record efficiency of almost 14% was reached for those types of reflectors on a large area 71 cm2 epitaxial Si solar cell, giving a boost in efficiency of 0.6% absolute in comparison with the solar cells containing conventional reflectors. [ABSTRACT FROM AUTHOR]