On the stability of a variety of organic photovoltaic devices by IPCE and in situ IPCE analyses – the ISOS-3 inter-laboratory collaboration

Abstract

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.

TOF-SIMS investigation of degradation pathways occurring in a variety of organic photovoltaic devices – the ISOS-3 inter-laboratory collaboration

“…Water release from PEDOT:PSS was suggested in the previous ISOS-3 reports. 16,17 The relative performance over time suggests significantly different degradation behaviour for the two devices, which is further supported by significantly different lifetimes. Photo-oxidation was most likely not an important factor for the overall device degradation, so other factors must have been in play for the ISE and Holst devices such as for example the degradation mechanisms proposed in the second and third ISOS-3 reports.…”

“…If photo-oxidation was not an important factor for the overall degradation, then other factors must have been in play for the ISE and Holst devices such as those suggested in the second and third ISOS-3 reports. 16,17 In the second ISOS-3 report it was suggested that for the Holst device elevated temperatures (85 AE 5 1C) caused by the sun simulator and additional heating of the cell due to current collection within the PEDOT:PSS could result in water being released from the highly conductive PEDOT:PSS, which consequently would react with the Al electrode, forming aluminium oxide. 16 Furthermore, in the third ISOS-3 report an additional degradation mechanism was proposed for the Holst device.…”

“…In the third article incident photon-to-electron conversion efficiency (IPCE) and in situ IPCE were employed to describe various degradation mechanisms. 17 The most important conclusions regarding degradation mechanisms based on the previous ISOS-3 reports are summarized in the following.…”

“…The result of the IPCE and in situ IPCE analyses resulted in the following major conclusions/ comments regarding degradation: 17 For some of the encapsulated devices the degradation could possibly be initiated at the Ag or Au/PEDOT:PSS interface by the formation of a chemical bond between the Ag (or Au) and the PEDOT:PSS, which can occur in the absence of oxygen and water.…”

Comparative indoor and outdoor degradation of organic photovoltaic cells via inter-laboratory collaboration

“…The demonstration of power conversion efficiencies (PCEs) over 10% and continuously improving in research cells from a variety of materials systems is a major achievement [4]. The issue of cell lifetime and an understanding of cell degradation have also been addressed in some laboratory studies [5][6][7][8][9][10][11][12], and a few outdoor tests [13][14][15]. Of the three major attributes needed, lifetime in realistic outdoor settings is probably the most significant challenge left to address.…”