Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A new ideality factor for perovskite solar cells and an analytical
  theory for their impedance spectroscopy response   Impedance spectroscopy (IS) is a relatively straightforward experimental
technique that is commonly used to obtain information about the physical and
chemical characteristics of photovoltaic devices. However, the non-standard
physical behaviour of perovskite solar cells (PSC), which are heavily
influenced by the motion of mobile ion vacancies, has hindered efforts to
obtain a consistent theory to interpret PSC impedance data. This work rectifies
this omission by deriving a simple analytic model of the impedance response of
a PSC from the underlying drift-diffusion model of charge carrier dynamics and
ion vacancy motion. Extremely good agreement is shown between the analytic
model and the much more complex drift-diffusion model in regimes (including
maximum power point) where the applied voltage is close to the open circuit
voltage $V_{oc}$. Both models show good qualitative agreement to experimental
IS data in the literature and predict many of the observed anomalous features
found in impedance measurements on PSCs, such as `the giant low frequency
capacitance` and `inductive arcs' in the Nyquist plots. Where the physical
properties of the PSC are already known the analytic model can be used to
predict the recombination current $j_{rec}$ and the high and low frequency
resistances and capacitances of the cell, $R_{HF}$, $C_{HF}$, $R_{LF}$ and
$C_{LF}$. In scenarios where the physical properties of the cell are unknown
the analytic model can also used to extract physical parameters from
experimental PSC impedance data. {A novel physical parameter of particular
significance to PSC physics is identified. This is termed the electronic
ideality factor, $n_{el}$, and (as opposed to the standard ideality factor) can
be used to deduce the dominant source of recombination in a PSC, independent of
its ionic properties.

36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph