## 1 Introduction  
The luminescent solar concentrator photovoltaic collector (LSC PV) shown in Figure 1 holds several attractive features over existing conventional PV modules that are usually dark in color and are of a fixed thin, flat and rectangular shape, and so cannot meet the design requirements for the proper integration of photovoltaic technologies in products and buildings--so-called building integrated PV (BIPV). On the other hand, LSCs support colorful surfaces, transparency and provide form freedom,offering many design opportunities to enhance the overall functionality and experience of PV power generation within consumer products, the built environment and transportation [1,2]. The LSC is a technology [3,4] for harvesting solar energy that is comprised of a transparent element which serves to guide light to PV solar cells. These cells act as the receivers for the solar irradiance and generate electrical power--a typical configuration of this is shown in Figure 1. The LSC lightguide, which is usually made of polymer, glass or another transparent material, has a refractive index that is higher than air and contains luminescent pigments or luminophores, often molecular dyes. Sunlight, either direct or diffuse, is absorbed by dye molecules and, upon re-radiation, is guided by total internal reflection (TIR) to the photovoltaic solar cells at the periphery of the solar cell. Combining the concentration of irradiance and the transformation of the incoming spectrum in one solar device offers the potential for an efficient energy conversion process. Typically, an ideal LSC PV consists of a host material with a higher transparency, and a low scattering and attenuation coefficient, that is compatible with the dispersal of luminescent dyes [5,6]. Moreover, the emission spectra of the luminophores should be matched with the spectral response of the solar cells [7]. In the past, however, LSC PV technologies have only shown moderate power conversion efficiencies (PCE), in the range of 2%-7% [1]. To date, these technologies have not been considered a serious alternative to conventional PV technologies. However, they do have the potential for an improved performance, while providing a design freedom that is difficult to achieve with conventional photovoltaic modules. The aim of this work, therefore, is to further develop the LSC PV elements for the enhancement of the product applications of PV, leading to higher efficiencies beyond the 10% threshold for LSC PV technologies that is often claimed in the literature [8]. Hitherto, various monofacial solar cells have been studied for their attachment to LSCs [9]. However, bifacial solar cells absorb the direct and diffuse irradiance impinging on the front and rear side, which increases the output power when compared to monofacial solar cells. This increase in power can exceed that of a monofacial cell by 35% and 70% under sunny and cloudy conditions, respectively [10,11]. This is because the output power of the bifacial cells depends on the albedo of its surroundings and, in particular, on the albedo of the surface underneath the backside of such a solar cell [12]. At the beginning of 2019, a summer school was organized on the topic of \"Exciton Solar + Design\", with the aim of cross-fertilizing scientific research on the control of molecular excitons with the design potential of LSC PV applications. This summer school was composed of scientists, students and design  
Figure 1: The design and working principle of a luminescent solar concentrator photovoltaic (LSC PV) element, with solar cells attached to the edges, showing the absorption spectrum (solid line) and the emission spectrum (dotted line) of a dye in an LSC. professionals and involved formal lectures, design exercises and practical outdoor field testing of LSC PV devices. Several conceptual designs from the 15 participants were developed and presented during this summer school. They were partially evaluated by the ray tracing simulations in order to explore their optical performance.