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Author ORCID ID is 0000000340705067
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  1. External quantum efficiency and transient photocapacitance (TPC) spectra were obtained for perovskite solar cells with methylammonium lead triiodide perovskite absorbers formed by either dip or vapor conversion. These measurements reveal an extended band of sub-gap states in all of the devices studied. The defect band is best fit by a pair of defects, and the appearance of the defect signal in the transient photocapacitance spectra indicates that at least one of the observed defects is in the perovskite absorber. The cells with the largest density of defect states show the lowest shortcircuit current density and open-circuit voltage for slow, quasi-steady-state,more » current density-voltage sweeps and the largest hysteresis in short-circuit current density for fast sweeps. In conclusion, this suggests that defect states in the perovskite absorber limit steady-state device performance, and that these defects or associated mobile charges play a role in the hysteresis observed in current density-voltage measurements.« less
  2. In this paper, we demonstrate that an analytic relationship between coefficients in the Taylor expansion of the junction capacitance can be exploited to yield more precise determinations of carrier densities in drive level capacitance profiling (DLCP). Improvements are demonstrated on data generated according to the DLCP theory and in measurements performed on a CuIn xGa 1–xSe 2 device. We argue that the improved DLCP method is especially important for non-uniform devices, which are more susceptible to noise in the capacitance data used in DLCP because they require that the amplitude of the drive level be restricted. Importantly, the analysis doesmore » not require the collection of any data other than what is typically collected during a DLCP measurement while employing fewer independent parameters than the model that is typically used in DLCP. Finally and thus, we expect that it will be readily adoptable by those who perform DLCP measurements.« less
  3. Conjugated polyelectrolytes and related mixed ionic-electronic conductors (MIECs) are being explored for energy applications including solid-state lighting and photovoltaics. Fundamental models of charge injection into MIECs have been primarily developed for MIECs contacted with highly conductive or metal electrodes (MEs), despite many potential applications involving semiconductors. We theoretically and experimentally demonstrate that an appropriate semiconductor electrode (SE), n-type for electron or p-type of hole injection, can limit injection into MIECs. When the SE is the injecting electrode and is under accumulation, there is little difference from a ME. When the SE acts as the extracting electrode, however, injection into themore » MIEC can be limited because a fraction of any applied bias must support charge depletion in the semiconductor rather than charge injection into the MIEC. In a ME/MIEC/SE system, this can lead to significant asymmetry in current-voltage and injected charge-voltage behavior.« less

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