• Energy Research

Abstract The outdoor performance monitoring of two types of perovskite solar cell (PSC) mini-modules based on two different absorbers - CH3NH3PbI3 (MAPI) and Cs0.05FA0.83MA0.17PbI(0.87Br0.13)3 (FMC) is reported. PSC modules displayed markedly different outdoor performance characteristics to other PV technologies owing to the reversible diurnal changes in efficiency, difference in temperature coefficient between absorber layers and response under low light conditions. Examination of diurnal performance parameters on a sunny day showed that whereas the FMC modules maintained their efficiency throughout the day, the MAPI modules peaked in performance during the morning and afternoon, with a strong decrease around midday. Overall, the MAPI modules showed a strongly negative temperature coefficient (TC) for PCE, whereas the FMC modules showed a moderate positive temperature coefficient performance as a function of temperature due to the increase in JSC and FF. Outdoor monitoring of the MAPI modules over several days highlighted that the reduced over the course of the day but recovered overnight. In contrast the FMC modules improved slightly during the daytime although this was too reversed overnight. This paper provides insight into how PSC modules perform under real-life conditions and consider some of the unique characteristics that are observed in this solar cell technology.

The proof of concept of using luminescent down shifting (LDS) layers as alternative UV filters for P3HT:PCBM OPVs is demonstrated using a lanthanide-based metal complex. The results are verified using a combination of indoor light soaking, with single cell devices, and outdoor performance monitoring, using a 16-cell monolithically connected OPV module. By applying the LDS layer, a ~5% relative enhancement in photocurrent is observed for both sets of devices. More significantly, indoor light soaking tests on single cell devices without encapsulation showed an 850% enhancement in the measured half-life (T50%). The OPV modules were encapsulated and tested for outdoor stability over a 70 day period in the Negev desert, Israel. The modules made with the LDS filter are shown to match the stability of those made with a commercial UV filter and outperform the modules with no filter applied, with a 51% enhancement in the measured stability (T75%). Significantly, the work provides clear experimental evidence that the LDS layer can act as a UV filter in OPVs without compromising the efficiency of the solar cell, thus providing an added benefit over commercial UV filters.

Accurate characterization and reporting of organic photovoltaic (OPV) device performance reniains one of the important challenges in the field. The large spread among the efficiencies of devices with the same structure reported by different groups is significantly caused by different procedures and equipment used during testing. The presented article addresses this issue by offering a new method of device testing using "suitcase sample" approach combined with outdoor testing that limits the diversity of the equipment, and a strict measurement protocol. A round robin outdoor characterization of roll-to-roll coated OPV cells and modules conducted among 46 laboratories worldwide is presented, where the samples and the testing equipment were integrated in a compact suitcase that served both as a sample transportation tool and as a holder and test equipment during testing. In addition, an internet based coordination was used via plasticphotovoltaics.org that allowed fast and efficient communication among participants and provided a controlled reporting format for the results that eased the analysis of the data. The reported deviations among the laboratories were limited to 5% when compared to the Si reference device integrated in the suitcase and were up to 8% when calculated using the local irradiance data. Therefore, this method offers a fast, cheap and efficient tool for sample sharing and testing that allows conducting outdoor measurements of OPV devices in a reproducible manner. (C) 2014 Elsevier B.V. All rights reserved.

The lamination of OPV modules to corrugated roof cladding has been undertaken.

Abstract Mixtures of luminescence downshifting (LDS) materials has been used to increase the efficiency of poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) bulk heterojunction solar cell. This layers convert more energetic photons to lower energies that are better matched with wavelength peak of the external quantum efficiency (EQE) of a P3HT:PC61BM solar cell. Experimental studies were used to optimise the optical properties of LDS layers including the maximum of absorbance and the photoluminescence quantum yield (PLQY). To provide the significant improvements, combinations of LDS mixtures were prepared to provide the greatest absorption and PLQY. The approach is shown to simultaneously improve the photocurrent and increase the lifetime of the device by absorbing UV light. By optimising the optical properties of the LDS mixture, a relative increase of about 20% in the photocurrent density produced by the P3HT:PCBM cell could be achieved, which to our knowledge is one of the most significant reported for OPVs.

Abstract A comparison of performance parameters for first, second and third generation PV technologies has been conducted. Organic photovoltaic (OPV) modules displayed markedly different outdoor performance characteristics to other PV technologies owing to the positive temperature coefficient, lower thermal mass and response under low light conditions. The linear relationship between irradiance and module temperature rise above ambient is studied, leading to calculation of values for the Ross coefficient for OPV modules. OPVs are shown to possess a lower Ross coefficient than poly-Si, due to the lower absorption of infrared radiation. The effect of wind speed on the Ross coefficient is also investigated, showing the effect that module structure has upon outdoor PV performance, with the OPV module cooling quicker under windy conditions than the poly-Si due to a lower thermal mass. A long term stability study on OPV modules with a silver nanowire-zinc oxide (AgNW-ZnO) composite front electrode has showed two phases of degradation: a short initial burn-in with significant drops in performance; followed by stabilisation and degradation progressing at a much slower rate. During the burn-in period the modules showed diurnal reversible degradation in the short circuit current (ISC), whereas open circuit voltage (VOC) and fill factor (FF) show a steady decline. The reversible degradation is assumed to be related to the desorption of oxygen from the ZnO layer during the day due to UV excitation, leading to an increase in trap formation and a drop in current generation capacity, followed by re-adsorption of the oxygen overnight.

Abstract Government edicts and national time bound policy directives are shaping the drive toward cost effective renewables such as photovoltaics (PV). Building Integrated Photovoltaics (BIPV) has the potential to provide significant energy generation by utilising the existing building infrastructure as a power generator, engendering a transformation shift from traditional energy sources. This research presents an innovative study on the industrial viability of utilising “rough” low carbon steel integrated with an Intermediate Layer (IL) to develop lower cost thin film BIPV products and is compared to existing commercial products. Consideration of the final product cost is given and potential business models to enter the BIPV are identified. The lab scale and upscaling elements of the research support the significant benefits of an approach that extends beyond the use of expensive solar grade steel. A state-of-the-art review of existing steel-based BIPV products is given and used as a benchmark to compare the new products. The results demonstrate that a competitively commercial product is viable and also highlight the strong potential for the adoption of a “rough” steel + IL focused approach to BIPV manufacture and a potential new direction to develop cost efficiencies in an increasingly competitive market.