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为低成本和低嵌入能源光伏模块提供了一条途径，该模块具有集成到建筑物和其他基础设施中以大规模产生清洁电力的潜力。有机光伏（OPV）引起了广泛的研究兴趣；在效率和制造技术方面取得了令人印象深刻的进步。卤化铅钙钛矿太阳能电池（PSC）基于一种新发现的活性层材料，随着最近设备结构和工艺的优化，PSC在启动寿命效率方面表现出了根本性的改善。然而，这两种技术类型都面临着运行中功率转换效率损失的挑战，尽管它们被认为能够稳定效率为15-20%。这种设备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，需要了解典型作业环境中效率损失的来源，包括使用初期和老化阶段。到目前为止，大多数关于新型光伏器件稳定性的研究都是对不同材料或器件结构在不同环境下性能参数演变的实证研究，科学关注主要集中在光活性层的氧化稳定性上。相对而言，很少有人关注电极和中间层，尽管这些层通常是第一个失效的，而且它们在一定程度上负责保护有源层。此外，大多数性能指标探测的是宏观器件性能，尽管成像方法已被用于观察老化过程中的非均质材料特性，但测绘技术尚未用于详细了解电流和电压损耗的化学、电化学和物理机制。本提案旨在开发一套相互关联的实验技术，以探索两种领先的可印刷光伏（PV）材料，有机光伏（OPV）和有机卤化物钙钛矿太阳能电池（PSCs）中器件退化和失效的基本机制。我们的方法是开发和适应二维映射技术，探测材料的局部化学和电子状态，并将它们与设备级电测量、结构表征和建模相结合，以分析降解机制，确定导致降解的局部条件，并设计策略以抑制失效机制的进展。绘图工具将被开发用于模块制造和质量控制。

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.