Executive Summary : | Perovskite solar cells are increasingly explored as an alternative for the existing c-Si based solar cell technology. Within a decade of active research, the efficiency of the order of 23% is reported by multiple research groups. While impressive gains have been achieved over the past few years both in terms of material quality and efficiency, however, many aspects of perovskite solar cells are yet to reach desired standards to convert it from an interesting lab research activity to a mature technology. To list a few, concerns related to stability, process tolerance, and scaling to large area cells should be addressed before this technology can be seriously considered for any PV deployment. These system level bottlenecks are significantly influenced by interface phenomena – presence of defect states, mobile ions at perovskite/contact layer interfaces and their influence on carrier collection and recombination and hence on the eventual time dependent efficiency. Indeed, this crucial role of interface phenomena is now identified as one key aspect that could influence a wide variety of phenomena ranging from S-type characteristics, hysteresis, time dependent efficiency degradation, carrier extraction by hole quenching contact layers like MoO3, PL quenching and influence of substrates, characterization techniques like Voc decay, charge extraction, Impedance spectroscopy, etc.
Currently, the theoretical efforts to address these issues remains scattered and are neither coherent nor comprehensive. More importantly, there exist a serious lack of a bottom-up approach that involves usage of models of increasing complexity to incrementally build insights and conceptual understanding that could aid interpretation and optimization of experimental results. Further, there exist no unifying formalism to understand and interpret the trends from multiple characterization techniques, and, as a result it is difficult to integrate the insights from such diverse characterization techniques in a complimentary manner.
We aim to address the above-mentioned shortcomings and propose to develop predictive capabilities to understand and address the influence of interface phenomena on the efficiency through multi-scale modeling. Beyond the direct relevance to perovskite solar cells, the models and insights from this research could be further extended to the design and optimization of other perovskite based optoelectronic devices like LEDs and photo-transistors where interface phenomena could play a dominant role. |