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@PHDTHESIS{Krckemeier:1044223,
      author       = {Krückemeier, Lisa},
      title        = {{Q}uantifying {R}ecombination {L}osses and {C}harge
                      {E}xtraction in {H}alide {P}erovskite {S}olar {C}ells},
      volume       = {669},
      school       = {RWTH Aachen University},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2025-03112},
      isbn         = {978-3-95806-835-3},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {vi, 286},
      year         = {2025},
      note         = {Dissertation, RWTH Aachen University, 2025},
      abstract     = {Due to their exceptional properties, halide perovskite
                      materials have emerged as promising candidates for efficient
                      and cost-effective photovoltaics, with some devices
                      approaching the performance of silicon solar cells after a
                      decade of research. Despite their remarkable progress,
                      perovskite solar cells suffer from several loss mechanisms
                      that limit their efficiency. However, the rapid development
                      of perovskite research has outpaced advances in analyzing
                      characterization techniques tailored to the unique
                      properties of this material class. Thus, understanding and
                      quantifying the losses within these devices remains
                      difficult, especially in terms of recombination losses and
                      charge-extraction dynamics. This work aims to bridge this
                      gap by proposing innovative approaches and providing tools
                      for analyzing charge-carrier dynamics, which will help
                      correctly interpret and quantify experimental data for
                      perovskite solar cells. The overarching motivation is to
                      contribute to the advancement of perovskite solar cell
                      technology by gaining a deeper understanding of fundamental
                      processes. Transient photoluminescence (TPL) and transient
                      photovoltage (TPV) are popular techniques for monitoring
                      charge-carrier dynamics and investigating recombination
                      losses in perovskites. However, the low doping density of
                      lead-halide perovskites often places the device in
                      high-level injection during these measurements, leading to
                      non-linear relationships between the recombination rates and
                      carrier densities. This behavior leads to challenges in the
                      use of a scalar charge-carrier lifetime as a figure of merit
                      to quantify recombination. Furthermore, the interpretation
                      of data from complete solar cells or multilayer samples is
                      highly challenging due to the superposition of various
                      effects that modulate the charge-carrier concentration.
                      These effects include bulk and interfacial recombination,
                      charge transfer and extraction, and capacitive charging or
                      discharging. While theoretical work on TPL decays in full
                      solar-cell devices has been published for other photovoltaic
                      technologies, a comprehensive theory dealing with the
                      specific situation in halide-perovskite devices is currently
                      missing. In this work, improved spectroscopic techniques
                      with a high dynamic range of data acquisition are combined
                      with time-dependent, numerical simulations with Sentaurus
                      TCAD to break down the complex behavior of charge-carrier
                      dynamics in perovskite solar cells. The dissertation
                      contributes to the field by proposing new methods and
                      analytical models for data analysis of perovskite solar
                      cells. One major contribution involves a comprehensive
                      analysis of transient photoluminescence and transient
                      photovoltage decays, considering non-linear dependencies of
                      the recombination rate on charge-carrier density. This
                      multi-method quantitative data analysis of transient
                      photoluminescence and transient photovoltage decays goes
                      beyond traditional mono-exponential fitting methods,
                      introducing an approach to derive differential decay times
                      as a function of charge-carrier density and quasi-Fermi
                      level splitting. Time-dependent, numerical drift-diffusion
                      simulations of various sample structures, including
                      perovskite films, multilayer systems, and complete devices,
                      provide visualization and explanation of the injection
                      dependence of the decay time and allow distinguishing
                      between different carrier-density-dependent regimes.
                      Building upon these insights, analytical equations are
                      developed that serve as good approximations to the simulated
                      and experimental decay-time functions. These analytical
                      equations facilitate data analysis and the extraction of key
                      material parameters, like trapassisted Shockley-Read-Hall
                      recombination coefficients, by removing the need to do
                      extensive numerical simulations. The analytical approach is
                      further expanded to include the extraction of charge
                      carriers by the interlayers and contacts, in addition to
                      recombination. A twocomponent model for small-signal
                      measurements is developed that is based on the analytical
                      solution of coupled linear differential equations via the
                      determination of eigenvalues. The model describes the
                      transient behaviour of chemical and electrical potentials
                      and allows us to connect the rise and decay times in
                      small-signal transientphotovoltage experiments to
                      recombination, extraction, and capacitive charging and
                      discharging effects, providing quantitative values for
                      recombination and extractiontime constants as a function of
                      voltage. Another part of this work is the development of a
                      standardized framework for reporting voltage loss in
                      perovskite solar cells, addressing the impact of perovskite
                      composition changes on the limiting open-circuit voltage,
                      and proposing a consistent reference. This approach,
                      approximating the radiative limit, requires only a single
                      measurement of the external quantum efficiency for its
                      calculation, and is therefore fast and easy to apply. The
                      study compares different band gap definitions used in the
                      literature, revealing a substantial impact on the ranking of
                      the voltage losses. The proposal of referencing open-circuit
                      voltages to the radiative limit enables a meta-analysis of
                      previously published perovskite solar cells. In addition, I
                      present inverted, planar MAPI solar cells with open-circuit
                      voltages exceeding 1.26V. The combination of dry lead
                      acetate and lead chloride precursors, along with optimized
                      hole and electron transport layers, suppresses both bulk and
                      surface recombination, which is confirmed by an
                      exceptionally high photoluminescence external quantum
                      efficiency exceeding $5\%$ in complete cells. These solar
                      cells serve as the basis for subsequent investigations of
                      device physics and characterization techniques. These
                      scientific contributions significantly expand the
                      state-of-the-art by offering innovative methodologies for
                      characterizing halide perovskite solar cells. The proposed
                      frameworks and analytical approaches not only fill existing
                      gaps in understanding the implications of unconventional
                      material properties, but also pave the way for more accurate
                      and comprehensive analysis in future perovskite research.},
      cin          = {IMD-3},
      cid          = {I:(DE-Juel1)IMD-3-20101013},
      pnm          = {1215 - Simulations, Theory, Optics, and Analytics (STOA)
                      (POF4-121)},
      pid          = {G:(DE-HGF)POF4-1215},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2509261220158.637798969945},
      doi          = {10.34734/FZJ-2025-03112},
      url          = {https://juser.fz-juelich.de/record/1044223},
}