The investigation of degradation of seven distinct sets (with a number of individual cells of n $ 12) of state of the art organic photovoltaic devices prepared by leading research laboratories with a combination of imaging methods is reported. All devices have been shipped to and degraded at Risø DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. Imaging of device function at different stages of degradation was performed by laser-beam induced current (LBIC) scanning; luminescence imaging, specifically photoluminescence (PLI) and electroluminescence (ELI); as well as by lock-in thermography (LIT). Each of the imaging techniques exhibits its specific advantages with respect to sensing certain degradation features, which will be compared and discussed here in detail. As a consequence, a combination of several imaging techniques yields very conclusive information about the degradation processes controlling device function. The large variety of device architectures in turn enables valuable progress in the proper interpretation of imaging results-hence revealing the benefits of this large scale cooperation in making a step forward in the understanding of organic solar cell aging and its interpretation by state-of-the-art imaging methods.

Layered V 2 O 5 hydrate has been applied as the hole transport layer (HTL) in organic solar cells (OSCs). V 2 O 5 is obtained from a sodium metavanadate solution in water under ambient conditions, resulting in a final thin film of formula V 2 O 5 $0.5H 2 O. The 0.5 water molecules are not removed from the V 2 O 5 layered structure unless the sample is heated above 250 C, which makes the thin film highly stable under real working conditions. The HTL was used in OSCs in the normal and the inverted configurations, applying metallic Ag as the back-metal electrode in both cases. Fabrication of both OSC configurations completely by solution-processing printing methods in air is possible, since the Al electrode needed for the normalconfiguration OSC is not required. The work function (WF) and band gap energy (BG) of the V 2 O 5 thin films were assessed by XPS, UPS and optical analyses. Different WF values were observed for V 2 O 5 prepared from a fresh V 2 O 5-isopropanol (IPA) solution (5.15 eV) and that prepared from a 24 hold solution (5.5 eV). This difference is due to the gradual reduction of vanadium (from V 5+ to V 4+) in IPA. The OSCs made with the V 2 O 5 thin film obtained from the 24 hold V 2 O 5-IPA solution required photoactivation, whereas those made with the freshly obtained V 2 O 5 did not. Outdoor stability analyses of sealed OSCs containing a V 2 O 5 HTL in either configuration revealed high stability for both devices: the photovoltaic response at T 80 was retained for more than 1000 h. Broader context Organic Solar Cells (OSCs) have achieved an impressive increase in power conversion efficiency in the past few years, with values above the 12% range. Yet, in order to be competitive with existing energy sources from fossil fuels and modern inorganic photovoltaic technologies, OSCs must reduce fabrication costs and improve its energy payback time (EPBT). To achieve the latter, the fabrication of OSCs by large scale, solution processing methods applying inexpensive, low temperature techniques is required. An important aim is the exclusion of toxic organic solvents, being water-based or alcohol-based solutions is highly desired. In this work, a layered V 2 O 5 hydrate has been applied as the hole transport layer in stable OSCs. V 2 O 5 is obtained from the dissolution of sodium metavanadate in water under ambient atmospheric conditions, resulting in a nal thin lm with the V 2 O 5 $0.5H 2 O formula. OSCs with normal and inverted conguration applying metallic Ag as the back metal electrode in both cases have been fabricated. The use of a Ag electrode eliminates the need for a highly reactive work function metal electrodes (Al, Ca) for the normal conguration OSC, and permits the fabrication of both OSC congurations completely by solution processing printing methods in air. Outdoor stability analyses of sealed devices showed high stability, maintaining the photovoltaic response at T 80 for more than 1000 h.

Seven distinct sets (n >= 12) of state of the art organic photovoltaic devices were prepared by leading research laboratories in a collaboration planned at the Third International Summit on Organic Photovoltaic Stability (ISOS-3). All devices were shipped to RISO DTU and characterized simultaneously up to 1830 h in accordance with established ISOS-3 protocols under three distinct illumination conditions: accelerated full sun simulation; low level indoor fluorescent lighting; and dark storage with daily measurement under full sun simulation. Three nominally identical devices were used in each experiment both to provide an assessment of the homogeneity of the samples and to distribute samples for a variety of post soaking analytical measurements at six distinct laboratories enabling comparison at various stages in the degradation of the devices. Over 100 devices with more than 300 cells were used in the study. We present here design and fabrication details for the seven device sets, benefits and challenges associated with the unprecedented size of the collaboration, characterization protocols, and results both on individual device stability and uniformity of device sets, in the three illumination conditions

This work is part of the inter-laboratory collaboration to study the stability of seven distinct sets of state-of-the-art organic photovoltaic (OPV) devices prepared by leading research laboratories. All devices have been shipped to and degraded at RISØ-DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. In this work, we apply the Incident Photon-to-Electron Conversion Efficiency (IPCE) and the in situ IPCE techniques to determine the relation between solar cell performance and solar cell stability. Different ageing conditions were considered: accelerated full sun simulation, low level indoor fluorescent lighting and dark storage. The devices were also monitored under conditions of ambient and inert (N 2 ) atmospheres, which allows for the identification of the solar cell materials more susceptible to degradation by ambient air (oxygen and moisture). The different OPVs configurations permitted the study of the intrinsic stability of the devices depending on: two different ITO-replacement alternatives, two different hole extraction layers (PEDOT:PSS and MoO 3 ), and two different P3HT-based polymers. The response of un-encapsulated devices to ambient atmosphere offered insight into the importance of moisture in solar cell performance. Our results demonstrate that the IPCE and the in situ IPCE techniques are valuable analytical methods to understand device degradation and solar cell lifetime.