Voltage bias stress effects in metal halide perovskites are strongly dependent on morphology and ion migration pathways

Abstract

We determined how morphology, electronic and interfacial interactions affect perovskite PVs under voltage bias stress. Our findings provide insights into the discrepancies in the solar cell efficiencies observed across many different research groups.

Metal Halide Perovskites as Emerging Thermoelectric Materials

“…Ion diffusion inside MHPs is yet another typical challenge, especially for the mixed-anion perovskites, which may influence their compositional stability. Applying an electric field, which is unavoidable during the measurement, leads to bias stress and ion migration, , which can lead to ion segregation and accelerated degradation of mixed-anion perovskites, as well the appearance of lattice defects, ion accumulation, and perovskite/metal contact degradation. Contact degradation arising from halide ion migration can occur due to atomic migration of the metal or the formation of metal compounds with halide anions such as AgI .…”

Interplay between Morphology and Electronic Structure in Emergent Organic and π-d Conjugated Organometal Thin Film Materials

“…Modern materials have pressed the envelope of what is achievable by semiconducting and conducting materials. This has necessitated the ability to deconvolute the intrinsic morphological and electronic complexities in terms of ionic charge transport, where next to traditional electronic transport ions can also migrate under a bias. , Ionic charge transport within materials can present advantageous or deleterious effects depending on the desired application. , It has in these cases become crucial to identify ion migration effects within materials.…”

“…Ionic charge transport can be investigated using voltage/current bias stress characterization methods. Application of a DC bias across a material creates a nonlinear transient effect typically in the form of an exponential decay or growth . This represents the migratory pattern of the ionic species, which upon saturation will exhibit an ohmic response.…”

“…Both of these platforms are of interest for their synthetic modularity, wherein the structural composition can be adapted for a desired property. These properties can be tailored to a range of device applications from traditional diode and transistor stacks to photovoltaic and thermoelectric devices or even more recently topological insulating spintronic and magnonic materials. ,,− The broad range of applications befitting of MHPs and MOFs has inspired a growing interest to understand these materials. This section focuses on advances observed in each of these emerging materials and details the role of morphology on their resultant properties.…”

“…An essential component of efficient charge transport in MHP thin films is to produce films of high quality. This requires tuning of the morphological properties including grain size, grain boundaries that are well passivated for better interfacial contact, continuity, and limited pinholes. , Moreover, the addition of Cl – ions has also been reported to induce larger grain sizes and preferred crystallite orientations within the MHP film. , The crystallite orientation of MHP thin films has recently been found to influence the possible ion migration pathways and therefore alter charge transport and electrical current stability within the MHP materials. Ion migration is the primary cause of bias stress effects in the form of internal current and voltage instabilities observed in MHPs.…”