High resolution mapping of performance and degradation mechanisms in printable photovoltaic devices

可以在低温下从溶液中加工的光伏材料提供了一条低成本、低嵌入能量的光伏组件的途径，有可能集成到建筑物和其他基础设施中，以大规模生产清洁电力。有机光伏(OPV)已经引起了强烈的研究兴趣；在效率和制造技术方面的令人印象深刻的改进已经被证明。卤化铅钙钛矿太阳能电池(PSC)基于一种新发现的有源层材料，最近对器件结构和工艺进行了优化，显示出寿命开始效率的根本改善。然而，这两种技术都面临着运行中的电力转换效率损失的挑战，尽管它们被认为能够稳定在15%-20%的效率。这种装置有限的运行稳定性阻碍了它们的广泛商业应用。为了克服这一问题，有必要了解在典型运行环境中，无论是在使用初期还是在老化过程中，效率损失的来源。到目前为止，对新型光伏器件稳定性的研究大多集中在对不同材料或器件结构在不同环境下的性能参数变化的实证研究，而科学关注的焦点主要集中在光活性层的氧化稳定性上。对电极和中间层的关注相对较少，尽管这些层通常是第一个失效的，而且它们还部分地负责保护有源层。此外，大多数性能指标探测宏观器件的性能，尽管已经使用成像方法来观察老化过程中的异质材料属性，但尚未使用映射技术来详细了解电流和电压损失的化学、电化学和物理机制。该提案旨在开发一套相互关联的实验技术，以探索两种主要的可打印光伏(PV)材料--有机光伏(OPV)和有机卤化物钙钛矿太阳能电池(PSC)--器件退化和失效的基本机制。我们的方法是开发和调整二维映射技术，探测材料的局部化学和电子状态，并将其与设备规模的电气测量、结构表征和建模相结合，以分析退化机制，确定导致退化的局部条件，并设计策略以抑制失效机制的发展。这些绘图工具将被开发出来，有可能在模块制造和质量控制中应用。

PV materials that can be processed from solution at low temperature offer a route to low cost and low emebedded energy PV modules with potential for integration into buildings and other infrastructure to generate clean electricity on a large scale. Organic PV (OPV) has attracted intense research interest; impressive improvements in efficiency and in fabrication knowhow have been demonstrated. Lead halide perovskites solar cells (PSC) are based on a newly rediscovered active layer material and have shown radical improvements in start-of-life efficiency with recent optimisation of device structure and processing. However both technology types are challenged by losses in power conversion efficiency under operation, even though they are believed capable of stabilised efficiency of 15-20%. The limited operational stability of such devices inhibits their widespread commercial application. To overcome this there is a need to understand the sources of efficiency loss, both at start-of-life and during ageing in typical operating environments. Until now, most studies of novel PV device stability have amounted to empirical studies of the evolution of performance parameters for different materials or device structures in different environments, and scientific attention has focussed largely on the oxidative stability of the photoactive layer. Relatively little attention has been paid to the electrodes and interlayers, even though these layers are often the first to fail and additionally they are partly responsible for protecting the active layers. In addition, most performance metrics probe the macroscopic device performance and although imaging methods have been used to observe heterogeneous material properties during ageing mapping techniques have not yet been used to provide detailed insight into the chemical, electrochemical and physical mechanism of current and voltage loss. This proposal seeks to develop a set of interlinked experimental techniques to probe the basic mechanisms underpinning device degradation and failure in two leading classes of printable photovoltaic (PV) materials, organic photovoltaics (OPV) and organohalide perovskite solar cells (PSCs). Our approach is to develop and adapt two-dimensional mapping techniques that probe the local chemical and electronic state of the materials and combine them with device-scale electrical measurement, structural characterisation and modelling in order to analyse the degradation mechanisms, to identify the local conditions that lead to degradation and to design strategies to inhibit the progression of failure mechanisms. The mapping tools will be developed with the potential to be applied during module manufacture and quality control.