Interlaboratory comparison of methodologies for measuring the angle of incidence dependence of solar cells

The aim of this work is to compare angle of incidence (AOI) measurement setups for solar cells between laboratories with such capability. For the first time, we compare relative light transmission measurements among eight laboratories, whose measurement techniques include indoor and outdoor methods. We present the relative transmission measurements on three 156 mm x 156 mm crystalline-Si (c-Si) samples with different surface textures. The measurements are compared using the expanded uncertainties provided by each laboratory. Five of the eight labs showed an agreement better than ±2% to the weighted mean between AOIs from -75° to 70°. At AOIs of ±80° and ±85°, the same five labs showed a worst case deviation to the weighted mean of -3% to 5% and 0% to 18%, respectively. When measurement uncertainty is considered, the results show that measurements at the highest incidence angle of ±85° are problematic, as measurements from four out of the six labs reporting uncertainty were found non-comparable within their stated uncertainties. At 85° AOI a high to low range of up to 75% was observed between all eight laboratories

Reduction of escape cone losses in luminescent solar concentrators with cholesteric mirrors

The Luminescent Solar Concentrator (LSC) consists of a transparent polymer plate containing luminescent particles. Solar cells are connected to one or more sides of the polymer plate. Part of the light emitted by the luminescent particles\u3cbr/\u3eis guided towards the solar cells by total internal reflection. About 25% of the dye emission is typically emitted within the optical escape cone of the matrix material and is lost due to emission from the top. We study the application of selectively-reflective cholesteric layers to reduce these losses. We have implemented these mirrors in the ray-tracing model for the LSC. The simulations show that an optimum in performance can be obtained by selecting an appropriate centre wavelength of the cholesteric mirror.\u3cbr/\u3eExternal Quantum Efficiency measurements were performed on LSC devices with a mc-Si, GaAs or InGaP cell and a dichroic mirror. This mirror shows a similar behavior as the cholesteric mirror. The results show that for a 5x5 cm2 LSC\u3cbr/\u3ethe mirror does improve the EQE in the absorption range of the dye

Luminescent solar concentrator photovoltaic designs

\u3cp\u3eThis paper discusses the opportunities and challenges of designing products using luminescent solar concentrator (LSC) photovoltaic (PV) technologies. The focus is on the integration of LSC PV technologies in PV modules, future products and buildings. It is shown that the typical material properties of LSCs — low cost, colorful, bendable, and transparency — offer a lot of design freedom. Two differently designed LSC PV modules with back contacted solar cells are presented including ray-tracing simulations and experimental results resulting from their prototypes. It is shown that the efficiency of a LSC PV module can be 5.8% with a maximum efficiency of 10%. Further the results of a design study which focused on product integration of LSC PV technologies are presented and discussed. In total 16 different and highly innovative conceptual designs resulted from this project, which were prototyped at scale to show their feasibility and integration features.\u3c/p\u3

Luminescent solar concentrator photovoltaic designs

This paper discusses the opportunities and challenges of designing products using luminescent solar concentrator (LSC) photovoltaic (PV) technologies. The focus is on the integration of LSC PV technologies in PV modules, future products and buildings. It is shown that the typical material properties of LSCs — low cost, colorful, bendable, and transparency — offer a lot of design freedom. Two differently designed LSC PV modules with back contacted solar cells are presented including ray-tracing simulations and experimental results resulting from their prototypes. It is shown that the efficiency of a LSC PV module can be 5.8% with a maximum efficiency of 10%. Further the results of a design study which focused on product integration of LSC PV technologies are presented and discussed. In total 16 different and highly innovative conceptual designs resulted from this project, which were prototyped at scale to show their feasibility and integration features

The solar noise barrier project 3. The effects of seasonal spectral variation, cloud cover and heat distribution on the performance of full-scale luminescent solar concentrator panels

We report on the relative performances of two large-scale luminescent solar concentrator (LSC) noise barriers placed in an outdoor environment monitored for over a year. Comparisons are made for the performances of a number of attached photovoltaic cells with changing spectral illumination, cloud cover conditions and other seasonal variations, and the temperatures of the cells. Differences in performance are attributed to the positioning of the panels, whether facing North/South or East/West. In general, the panels facing East/West run cooler than those facing North/South. The LSCs in both orientations appear to perform more efficiently under lower light conditions: one factor contributing to this increased performance is better spectral matching of the solar spectrum under cloudy conditions to the absorption spectrum of the embedded fluorescent dye. This work is a step forward in the characterization of a large scale LSC device, and suggests predictions of performance of devices could be made for any location given sufficient knowledge of the illumination conditions, and provides an important step towards the commercialization of these alternative solar energy generators for the urban setting

The solar noise barrier project 4:modeling of full-scale luminescent solar concentrator noise barrier panels

\u3cp\u3eA full-size (1 × 5 m\u3csup\u3e2\u3c/sup\u3e) luminescent solar concentrator (LSC) has been constructed and the edge electric outputs from the attached photovoltaic cells monitored for a period of slightly over one year in the solar noise barrier (SONOB) “living lab” outdoor environment. The results of the edge electric output measurements were compared to ray-tracing simulations, revealing imperfections in the system design and production that resulted in the significantly reduced performance of the panel compared to expectations. Results of these calculations suggest edge emission improvements of a factor of 6–9 are possible: at these improved edge outputs, the LSC becomes a viable solar energy generator for the built environment, with significant visual appeal. A grey-box computer model has been developed to predict LSC performance using a realistic device design with reduced internal light scattering and better photovoltaic cell positioning. A second model is used for extrapolation of the LSC solar barrier electric performance with different orientations in different world locations.\u3c/p\u3

Improving polymer based photovoltaic devices by reducing the voltage loss at the donor-acceptor interface

The costs of large area, organic photovoltaic devices are stronly related to their module efficiency. Even for niche markets, such as consumer electronics, efficiency is imperative since the available area is limited. Therefore, if polymer photovoltaics is to become a mature technology, it is key to increase the power conversion efficiency of the devices. In our contribution an analysis is given of the energy loss factors in P3HT:[C6O]PCBM cells. The main loss occurs as a voltage loss at the donor-accpetor interface. Since this loss factor is linked to the HOMO-LUMO levels of the system, it is impossilble to reduce this loss using the same material combination. We present polymer: [C6O]PCBM cells with similar optical properties but with a reduced voltage loss at the interface, leading to enhanced open circuit Voltage of 1.0 V (compared to 0.62 V for P3HT:[C6O]PCBM devices). The polymer is an alternating copolymer with fluorence and benzothiadiazole units (PFTBT). Well-characterised devices yield already an AM 1.5 efficiency of 4%, thus competing with state-of-the-art P3HT:PCBM devices