Methods for Improving the Lifetime Performance of Organic Photovoltaics with Low‐Costing Encapsulation

Abstract

Recent years have seen considerable advances in organic photovoltaics (OPVs), most notably a significant increase in their efficiency, from around 4 % to over 10 %. The stability of these devices, however, continues to remain an issue that needs to be resolved to enable their commercialization. This review discusses the main degradation processes of OPVs and recent methods that help to increase device stability and lifetime. One of the most effective steps that can be taken to increase the lifetime of OPVs is their encapsulation, which protects them from atmospheric degradation. Efficient encapsulation is essential for long-term device performance, but it is equally important for the commercialization of OPVs to strike a balance between achieving the maximum device protection possible and using low-cost processing for their encapsulation. Various encapsulation techniques are discussed herein, with emphasis on their cost effectiveness and their overall suitability for commercial applications.

Cellular Automata Modelling of Photo-Induced Oxidation Processes in Molecularly Doped Polymers

“…As the purpose of the CA model is to consider photo-dynamical processes within each cell it is also necessary to establish the number of photons (NP j,i ) that exist at each cell location at any instant. This was accomplished by first assigning a cellular absorption coefficient (αs j,i ) to each cell according to its particular occupation state (s = 0, 1, 2 or 3 as defined by the cellular numerical codes), and calculating the number of photons for all cells in the first row (NP 0,i ) according to the required photon flux and CA cellular area (∆L) 2 . For all sub-surface Coatings 2016, 6, 55 3 of 11 cells in each column, the number of photons may then be continuously updated throughout the CA simulation by applying de-Beer's law [7] …”

“…Coatings 2016, 6, 55 3 of 10 in the first row (NP0,i) according to the required photon flux and CA cellular area (L) 2 . For all subsurface cells in each column, the number of photons may then be continuously updated throughout the CA simulation by applying de-Beer's law [7] such that NPj,…”

“…They also provide an ideal system to study fundamental electronic transport mechanisms which frequently involve inter-molecular reduction-oxidation processes that are initiated by photo-stimulation. The unavoidable presence of soluble oxygen in MDPs may, however, initiate irreversible chemical conversion of photo-excited dopant molecules to a new molecular by-product with associated degradation of the original MDP electronic performance [2]. The ability to predict the potential degradation of proposed MDP constituents should therefore be of interest for commercial applications where operational photo-excitation of the molecular dopant exists.…”

Baselines for Lifetime of Organic Solar Cells

“…Meanwhile, rapidly developing emerging PV technologies, such as organic photovoltaics (OPV), dye sensitized solar cells (DSSC), perovskite solar cells (PVSK) and others alike still lack standard testing methodologies that would allow reliably predicting their performance in the end use environment. The reason partly comes from the fact that the emerging PVs considerably differ in architecture from their inorganic counterparts [1] and due to their increased sensitivity towards the testing environments [2][3][4][5] the common testing standards are not suitable for these technologies [6]. In addition, standards are requirements and recommendations that are created by bringing together the best practices and many experiences of various expert groups in the field, and due to the relatively young age of the emerging technologies and lack of controllable testing procedures there has not been generated sufficient amount of reliable data so far that could lay the basis for development of standards.…”

Trap Generation Dynamics in Photo-Oxidised DEH Doped Polymers

“…Degradation phenomena are commonly manifested through prolonged device operation under normal ambient conditions and often involve irreversible oxidation processes that are initiated via molecular excitation. Considerable technological effort has therefore focused either upon chemical modification of the active polymer to improve stability, or more robust encapsulation of plastic devices which are deployed under normal environmental conditions [4]. Whilst such strategies have generally improved the operational lifetime of plastic electronic products to fulfill acceptable commercial benchmarks there remain many optoelectronic applications where alternative measures to minimise residual degradation artifacts must be sought.…”