Abstract
Recent work of ten different groups shows that the application of zinc-halides in lead perovskite materials results in a contraction of the d-space, stronger interaction with the organic cation, improved crystallization with larger crystal domains, a Goldschmidt factor closer to unity, smoother and denser thin films and an even distribution of Zn(II) (at the Pb(II) sites) throughout the material. These combined effects may lead to: (1) a substantially higher stability (even at ambient or high humidity conditions); (2) enhanced luminescent properties; (3) a higher power conversion efficiency (PCE) of the corresponding solar cell devices (up to PCE ~20%, with enhancement factors of 1.07 to 1.33 relative to undoped material).
Highlights
Perovskite Solar Cells on the RiseThe search for novel photovoltaic materials has intensified over the past few decades as the demand for cleaner energy sources grows
Perovskites have received a tremendous amount of attention, since these materials provide a cheap route to highly efficient photovoltaic materials
To fully confirm that Zn is incorporated in the lattice X-ray diffraction measurements were carried out at different concentrations of Zn2+ : upon increase of the Zn2+ content the peak representing the 110 plane is slightly shifted to a higher degree, which indicates that the d-space of cells contract when they are doped with Zn
Summary
The search for novel photovoltaic materials has intensified over the past few decades as the demand for cleaner energy sources grows. Ions at the B-site of the perovskite crystal lattice It remains elusive how partial substitution of the lead ions in the B-site with a particular alternative metal species influences the material properties and photovoltaic performance. The smaller ionic radius of Zn(II) compared to Pb(II) causes a unit cell contraction of the hh0-plane and this results in enhanced nucleation and crystallization during fabrication, resulting in bigger grains and fewer pinholes This is beneficial for efficiency because non-radiative losses are generally attributed to Grain Boundaries (GBs), so by reducing the number of GBs (due to the enlargement of perovskite domains) losses are reduced. This induces increased stabilization of the resulting film towards degradation, which commences at grain boundaries and at pinholes. For more background information on perovskites and their solar cells we refer to several extensive recent reviews on this general topic [17,18,19]
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