Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
DOI: https://doi.org/10.29363/nanoge.hopv.2022.019
Publication date: 20th April 2022
In order to further improve the efficiencies and in particular the open-circuit voltages of perovskite solar cells it is important to understand non-radiative recombination and their relation to defect densities. In this talk, I will discuss our recent findings on how to measure and quantify both defect densities and decay times as an assay of the strength of recombination. Defect densities are often measured using methods that rely on measuring the charge density on these defects. Examples for such methods are capacitance-based methods as well as the measurement of unipolar current voltage curves (often called space charge limited current measurements) where the voltage onset of the trap-filled limit is evaluated. All these methods are typically done on sandwich-type devices where the volume charge densities have to compete with the charge per area on the electrodes. If the volume densities are too low to cause a Debye length that is shorter than the thickness of the semiconductor between the electrodes, the volume charge of the defects would not affect the measurement. I show that this is likely often the case in thin-film devices but not in single crystals. Therefore, these methods create an artificial bias towards assigning higher defect densities to thin films than to single crystals.1-2
A striking observation in the context of measuring recombination lifetimes is the huge discrepancies that are typically reported for lifetimes measured on films and on devices. Typically, the devices show longer lifetimes despite the fact that they have more interfaces and typically higher recombination rates at a given Fermi level splitting than well passivated films. This initially surprising feature can be understood by studying the differences between actual lifetimes due to recombination and a more general concept of decay times that may be due to recombination, extraction, injection and capacitive charging and discharging of electrodes. We develop a reasonably simple analytical set of equations to describe decay times in electrical and optical transient measurements.3-4
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International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.