Herramientas de simulación de células solares avanzadas

Resumen

Perovskite solar cells (PSCs) have attracted considerable research interest because they exhibit a series of distinctive features in their optoelectronic response which have a crucial in uence on the performance, particularly for long-time response. A survey of recent advances, both in device simulation and optoelectronic and photovoltaic responses, is provided in this thesis, with the aim of comprehensively covering these recent advances. Device simulations are included with clarifying discussions about the implications of classical drift{di usion modeling and the inclusion of ionic charged layers near the outer carrier selective contacts. Hysteresis in current-voltage curves is also studied here. Although alternative models and explanations are included in the discussion, the work relies upon a key mechanism able to yield most of the rich experimental responses. Particularly for state-of-the-art solar cells exhibiting e ciencies around or exceeding 20 %, outer interfaces play a determining role on the PSC's performance. The ionic and electronic kinetics in the vicinity of the interfaces, coupled to surface recombination and carrier extraction mechanisms, should be carefully explored to progress further in performance enhancement. Knowledge of the mechanisms that take place at the selective contacts, located at the chargetransport- layer (CTL)/perovskite heterojunctions, is crucial for the optimization of perovskite solar cells. Anomalous high values of the low-frequency capacitance at open-circuit and short-circuit indicate a high accumulation of charge at the interfaces, which could hinder the extraction of charge and increase hysteresis in current-voltage curve. To investigate this issue, a simulation model based on the drift-di usion di erential equations with speci c boundary conditions at the interfaces has been developed. The CTL/perovskite structures has been simulated as part of the entire perovskite solar cell, in order to establish the realistic energy pro le across the interfaces. The energy pro le allows to detect in which situations free charge accumulation at the interfaces exists, and to quantify this accumulation as a function of the device and material parameters. The role and the importance of each CTL/perovskite interface at open-circuit and short-circuit is also discussed. The conclusion is that the accumulation of charge at the interfaces is strongly a ected by the speci c contact materials, and critically depends on a compromise between the presence of ions, the values of the carrier mobility, and the interfacial and bulk recombination parameters. Modeling the transfer of charge that occurs at the interfaces of the charge-transport-layer (CTL)/perovskite heterojunctions is esential for accurately describing the performance of perovskite solar cells (PSCs). Anomalous high values of the low-frequency capacitance at open-circuit and shortcircuit indicate a high accumulation of charge at the interfaces, which can be linked to hysteresis in current-voltage (J-V) curves. Past experiments measuring dark current indicate that by modifying the type of selective contact, it is possible to suppress the capacitive contribution of the current and reduce the J{V cycling hysteresis. To investigate the physical origin of these experimental facts, a simulation model based on the drift-di usion di erential equations with a speci c treatment of the interfaces is developed. The role and the importance of using a proper interface recombination model on the performance of PSCs under dark conditions is discussed. In this regard, di erent interface recombination mechanisms proposed in the literature are considered. In addition, a new recombination model is proposed; this model considers the existence of a non-abrupt perovskite/CTL interface, in which band-to-band crossed recombination takes place, and is characterized by a speci c e ective bandgap and a speci c thickness. Moreover, resistive losses are incorporated in the simulation in order to achieve similar order of magnitude to those obtained in experimental current densities. This model is able to reproduce medium/high-frequency hysteretic e ects observed in experimental current-voltage curves. We show the importance of considering a realistic recombination model at the interfaces in order to interpret experimental hysteretic currents in darkness, and to quantify the role played by the selective contacts in these experiments.