## The effective acceptance angle

According to the definition given in section 13.1.2 for the acceptance angle a, 100% of the rays within the acceptance angle cone are collected. This acceptance angle lacks practical interest for two reasons. First, because an optical efficiency better than that with which the geometric rays are collected must be considered. Therefore, the discussion must […]

## Optical efficiency

A first definition of the optical efficiency [6, 8], nopt, i, is the light power transmission efficiency through the concentrator up to the cell surface for light rays impinging at the entry aperture from a given nominal direction v (usually refer to as the normal incidence). This definition is wavelength dependent and cell independent. A […]

## Geometrical concentration

The different possible definitions of the geometrical concentration come from the definitions of both the entry aperture area and cell area. With respect to the concentrator entry aperture area, sometimes the fully occupied area AE, full (for instance, the one defined to tessellate concentrator units) is used, while other times, if a portion of the […]

## Definitions of geometrical concentration and optical efficiency

Several definitions of both the geometrical concentration Cg and optical efficiency nopt of PV concentrators are commonly used in the literature. Of course, the definitions do not affect the device performance and cost but this situationmay be confusing for the interested reader when trying to compare different concentrators. We will briefly discuss about these definitions […]

## Concentration and acceptance angle

Concentrators can be accurately analysed in the framework of geometrical optics, where the light can be modelled with the ray concept. This is deduced from statistical optics [5], in which geometrical optics appears as the asymptotic limit of the electromagnetic radiation phenomenon when the fields can be approximated as globally incoherent (also called quasi-homogeneous). In […]

## Desired characteristics of PV concentrators

The next-generation concepts need concentrators for which the features are, in many cases, not yet fully defined. It seems that most of the present next- generation devices will need the same features as those required for the present PV concentration cells and, thus, we will refer to them here. The PV concentrator constitutes a specific […]

## Concentrator optics for the next-generation photovoltaics

P Benitez and J C Minano Institute de Energia Solar—Universidad Politecnica de Madrid ETSI TelecomunicaciOn Ciudad Universitaria s/n—28040 Madrid, Spain 13.1 Introduction Next-generation photovoltaic (PV) converters aim to be ultra-high efficiency devices. In order to be so efficient, it is expected that the cost of these converters will also be very high per unit area. […]

## Germanium layer transfer for photovoltaic applications

Multi-junctions solar cells can be processed on germanium substrates. However, these substrates are very expensive and the possibility of replacing them with germanium layers bonded on silicon substrates has been studied [10]. The process used consists in implanting H+ ions into germanium, to bond the implanted germanium wafer to a virgin silicon wafer and splitting […]