Recent Progress of Light Intensity‐Modulated Small Perturbation Techniques in Perovskite Solar Cells

Abstract

The small perturbation frequency‐resolved techniques have been powerful tools in unraveling the kinetic processes governing the operation of perovskite solar cells (PSCs). One such technique is electrochemical impedance spectroscopy (EIS). However, a thorough interpretation of the EIS response of PSCs is still lacking owing to the absence of a uniform electrical equivalent circuit. In this context, intensity‐modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) can be the link between the optical and electrical responses of PSCs and complement the IS technique. In this review, the progress made in interpreting the IMPS/IMVS response of various types of PSCs is summarized and diverse prospects are discussed. First, the basic theory and models present in the literature are discussed. Next, the IMPS/IMVS response of mesoporous and planar PSCs based on various physical parameters is discussed. At last, proposed future prospects for the development of this field are discussed.

Radiative Recombination Processes in Halide Perovskites Observed by Light Emission Voltage Modulated Spectroscopy

“…[ 42–46 ] The classical frequency‐resolved methods that use a sinusoidal photon flux $${\hat{\Phi }_{{\rm{in}}}}$$ impinging on the sample, are intensity‐modulated photocurrent spectroscopy (IMPS), and the intensity‐modulated photovoltage spectroscopy (IMVS). IMPS is described by the transfer function of current to light flux, [ 47–50 ] $\[Q\; = \;\hat{I}/q{\hat{\Phi }_{{\rm{in}}}}\]$. Here q is the elementary charge so that the incoming light flux (Φ in in N s −1 , where N is a number of photons), is expressed as an electrical current $\[q{\hat{\Phi }_{{\rm{in}}}}\]$.…”

Beyond Protocols: Understanding the Electrical Behavior of Perovskite Solar Cells by Impedance Spectroscopy

“…IMPS and IMVS are often considered as complementary techniques to alleviate the complexity of EC modeling in IS with the type of perturbation distinguishing IS from IMPS/IMVS. [ 141,142 ] A small, sinusoidal voltage perturbs the PSC in IS, whereas a small sinusoidal light perturbation is employed in IMPS/IMVS. IMPS and IMVS experiments are carried out under the same DC conditions (e.g., bias, temperature, illumination, humidity) and the small light perturbation of power density $${\tilde{P}}_{{\mathrm{in}}}\ ( t ){\mathrm{\, = \,}}| {{{\tilde{P}}}_{{\mathrm{in}}}} |{\mathrm{\ exp}}[ {i\omega t} ]$$ is added to the given DC incident light power density $${\bar{P}}_{{\mathrm{in}}}$$.…”

“…[ 143 ] While IS analyzes transport and recombination processes in the same measurement, IMVS and IMPS have often been used for PSCs to separately characterize recombination and charge transport processes. [ 142 ] IMPS measures the photocurrent responsivity of PSCs under short circuit condition, whereas for IMVS the photovoltage responsivity of the devices is measured as a function of small light perturbation at zero current, open circuit condition. The Nyquist spectra for IMPS/IMVS show multiple arcs and loops at low frequency part and this region has been the focus of studies to gain useful information about recombination/transport of the PSCs.…”

Correcting unintended changes in electroluminescence perturbation for reliable light intensity modulated spectroscopies

“…Commonly, IMPS and IMVS spectra are shown in Nyquist representation, where the respective transfer functions are plotted representing the negative imaginary parts -Q′' and -W′', as a function of the real parts, Q′ and W′ (see figure 1). In this representation, most typical spectra include one or several arcs in the first quadrant [3,4,19] and, in some cases, loops and/or tails in the second [4,20] and/or the fourth quadrant [21,22].…”