Improving the long-term stability of perovskite solar cells is critical to the deployment of this technology. Despite the great emphasis laid on stability-related investigations, publications lack consistency in experimental procedures and parameters reported. It is therefore challenging to reproduce and compare results and thereby develop a deep understanding of degradation mechanisms. Here, we report a consensus between researchers in the field on procedures for testing perovskite solar cell stability, which are based on the International Summit on Organic Photovoltaic Stability (ISOS) protocols. We propose additional procedures to account for properties specific to PSCs such as ion redistribution under electric fields, reversible degradation and to distinguish ambient-induced degradation from other stress factors. These protocols are not intended as a replacement of the existing qualification standards, but rather they aim to unify the stability assessment and to understand failure modes. Finally, we identify key procedural information which we suggest reporting in publications to improve reproducibility and enable large data set analysis.

This paper describes the measurement of photovoltaic module performance over a range of temperatures and irradiances according to the international standard IEC 61853 Part 1. The purpose of this work is to assess the reproducibility of power matrix measurements obtained using two methods specified in the standard: under natural sunlight with a tracker, and with a solar simulator. A comparison of results using the third principal method (under natural sunlight without tracker) is also summarised for completeness. The same measurement techniques have been employed to measure four modules of different technologies, namely mono and poly crystalline Si, CdTe and CIS. The method used to vary the irradiance in the natural sunlight with tracker and solar simulator approaches is based on un-calibrated mesh filters. The uniformity and effect on spectrum of the mesh filters have been studied, and the impact of these on the measurements estimated. Measurements from all methods are compared over as much of the ranges as possible. The results show that for all modules, the reproducibility is within the estimated measurement uncertainty. The suitability of the different methods is discussed in light of the results and the limitations of the various methods as applied to different modules technologies. On the basis of the results, parts of IEC 61853 Part 1 will be introduced into the ISO 17025 laboratory accreditation at the European Solar Test Installation (ESTI).

No abstract

Performance measurements of photovoltaic devices, including metastable ones, should reflect as closely as possible the behaviour of these devices when deployed in the field, i.e. at constant illumination and fixed conditions. We review the wide-ranging behaviour observed in and previously proposed measurement solutions for perovskite solar cells (PSC) devices and further illustrate the variability during measurement with recent examples from our own experience. We propose a generic measurement protocol for PSC devices to ensure that electrical characterisation under simulated sunlight reflects real life conditions. The approach focusses on determining the steady-state maximum-power output under continuous illumination rather than relying on the I–V characteristics. Given the large variations in device behaviour, this protocol is particularly suitable in cases where a priori information about the devices under test is not available. We conclude that the approach to the electrical characterisation of PSC devices should shift from traditional I–V curves to the maximum-power output under steady-state conditions. The latter is the simplest and most reliable method to evaluate, assess and compare PSC technologies when power and efficiency reporting are required. This protocol also contributes to harmonising comparison between different calibration laboratories thus contributing to increased confidence in the results.

Accuratecharacterizationandreportingoforganicphotovoltaic(OPV)deviceperformanceremainsone\ud of theimportantchallengesinthe field. Thelargespreadamongtheefficiencies ofdeviceswiththesame\ud structure reportedbydifferentgroupsissignificantly causedbydifferentproceduresandequipment\ud used duringtesting.Thepresentedarticleaddressesthisissuebyofferinganewmethodofdevice\ud testing using “suitcase sample” approach combinedwithoutdoortestingthatlimitsthediversityofthe\ud equipment,andastrictmeasurementprotocol.Aroundrobinoutdoorcharacterizationofroll-to-roll\ud coated OPVcellsandmodulesconductedamong46laboratoriesworldwideispresented,wherethe\ud samples andthetestingequipmentwereintegratedinacompactsuitcasethatservedbothasasample\ud transportation toolandasaholderandtestequipmentduringtesting.Inaddition,aninternetbased\ud coordination wasusedviaplasticphotovoltaics.orgthatallowedfastandefficient communicationamong\ud participants andprovidedacontrolledreportingformatfortheresultsthateasedtheanalysisofthe\ud data. Thereporteddeviationsamongthelaboratorieswerelimitedto5%whencomparedtotheSi\ud referencedeviceintegratedinthesuitcaseandwereupto8%whencalculatedusingthelocalirradiance\ud data. Therefore,thismethodoffersafast,cheapandefficient toolforsamplesharingandtestingthat\ud allowsconductingoutdoormeasurementsofOPVdevicesinareproduciblemanner

No abstract

This study addresses the issue of poor intercomparability of measurements of organic photovoltaic (OPV) devices among different laboratories. We present a round robin performance testing of novel OPV devices among 16 laboratories, organized within the framework of European Research Infrastructure Project (SOPHIA) and European Energy Research Alliance (EERA). Three types of OPVs with different structures, dimensions and encapsulations are studied and compared with reference Si solar cells certified by accredited laboratories. The agreement of the measurements of these among different laboratories is analyzed by focusing on testing procedures, testing equipment and sample designs. A number of deviations and pitfalls are revealed and based on the analyses, a set of recommendations are suggested for improving the agreement among the measurements of such OPV technologies

Incident solar radiation modelling has become of vital importance not only in architectural design considerations, but also in the estimation of the energy production of photovoltaic systems. This is particularly true in the case of buildings with integrated photovoltaics (PV) systems having a wide range of orientations and inclinations defined by the skin of the building. Since solar radiation data at the plane of interest is hardly ever available, this study presents the analysis of two of the most representative transposition models used to obtain the in-plane irradiance using as input data the global and diffuse irradiation on the horizontal plane, which can be obtained by satellite-based models or ground measurements. Both transposition models are validated with experimental measurements taken in Murcia (southeast of Spain) and datasets provided by the photovoltaic geographical information system (PVGIS) and the National Renewable Energy Laboratory (NREL) for vertical surfaces facing the four cardinal points. For the validation, the mean bias deviation, root mean square error and forecasted skill were used as indicators. Results show that the error rate decreases slightly for clear days. Better results are also obtained by dismissing data with low solar elevation angles so as to avoid shadowing effects from the surroundings in the early and late hours of the day, which affects mainly the performance of the transposition models for west and east surfaces. The results highlight the potential of equator-facing façades in winter time when the received irradiation can be twice as much as the one collected by the horizontal plane. It is also noteworthy that the operating conditions of all façades are mainly low irradiance and medium temperature at these locations.