Shuaifeng Hu

Abstract:

Perovskite interfaces critically influence the final performance of the photovoltaic devices. Optimizing them by reducing the defect densities or improving the contact with the charge transporting material is key to further enhance the efficiency and stability of perovskite solar cells. Inverted (p-i-n) devices can particularly benefit here, as evident from various successful attempts. However, every reported strategy is adapted to specific cell structures and compositions, affecting their robustness and applicability by other researchers. In this work, we present the universality of perovskite top surface post-treatment with ethylenediammonium diiodide (EDAI₂) for p-i-n devices. To prove it, we compare devices bearing perovskite films of different composition, i.e., Sn-, Pb-, and mixed Sn-Pb-based devices, achieving efficiencies of up to 11.4, 22.0, and 22.9%, respectively. A careful optimization of the EDAI₂ thickness indicates a different tolerance for Pb- and Sn-based devices. The main benefit of this treatment is evident in the open-circuit voltage, with enhancements of up to 200 mV for some compositions. In addition, we prove that this treatment can be successfully applied by both wet (spin-coating) and dry (thermal evaporation) methods, regardless of the composition. The versatility of this treatment makes it highly appealing for industrial application, as it can be easily adapted to specific processing requirements. We present a detailed experimental protocol, aiming to provide the community with an easy, universal perovskite post-treatment method for reliably improving the device efficiency, highlighting the potential of interfaces for the field.

Abstract:

<jats:p>This study pioneers a solvent-additive cascade strategy to achieve crystallographically homogenous perovskite films, breaking the efficiency–stability trade-off by harnessing facet-dependent properties for record performance.</jats:p>

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Abstract:

<jats:title>Abstract</jats:title><jats:p>The properties of metal‐centred species in metal halide perovskite precursor solutions substantially influence the formation and evolution of colloidal particles, which in turn dictate the crystallisation process and the film quality. In this work, we assess the “hard” and “soft” Lewis acid characteristics of Sn<jats:sup>2+</jats:sup> and Pb<jats:sup>2+</jats:sup> cations as a strategy to modulate the chemical environment of these metal‐containing species in mixed‐metal tin–lead perovskite precursor solutions. We observe enhanced simultaneous access to both metal centres upon adding compounds with functional groups suggested by the hard–soft acid–base principle. Theoretical calculations suggest that the hard base carboxyl group preferentially interacts with Sn<jats:sup>2+</jats:sup>‐based species, while the softer base thiol group also targets Pb<jats:sup>2+</jats:sup>‐based species. By effectively accessing and manipulating possible classes of inorganic species and their colloidal particle properties in the precursor solutions, we achieve 1.26 eV perovskite polycrystalline films exhibiting enhanced structural and optoelectronic quality, giving the best quasi‐Fermi level splitting values of up to 0.95 eV. As a result, the solar cell devices demonstrate efficiency values of up to 23.3% with an extended operational lifetime, retaining 80% of their initial efficiency after over 280 and 180 h of maximum power point tracking under simulated AM1.5G illumination at 25 and 65 °C, respectively.</jats:p>

Abstract:

The properties of metal‐centred species in metal halide perovskite precursor solutions substantially influence the formation and evolution of colloidal particles, which in turn dictate the crystallisation process and the film quality. In this work, we assess the “hard” and “soft” Lewis acid characteristics of Sn2+ and Pb2+ cations as a strategy to modulate the chemical environment of these metal‐containing species in mixed‐metal tin–lead perovskite precursor solutions. We observe enhanced simultaneous access to both metal centres upon adding compounds with functional groups suggested by the hard–soft acid–base principle. Theoretical calculations suggest that the hard base carboxyl group preferentially interacts with Sn2+‐based species, while the softer base thiol group also targets Pb2+‐based species. By effectively accessing and manipulating possible classes of inorganic species and their colloidal particle properties in the precursor solutions, we achieve 1.26 eV perovskite polycrystalline films exhibiting enhanced structural and optoelectronic quality, giving the best quasi‐Fermi level splitting values of up to 0.95 eV. As a result, the solar cell devices demonstrate efficiency values of up to 23.3% with an extended operational lifetime, retaining 80% of their initial efficiency after over 280 and 180 h of maximum power point tracking under simulated AM1.5G illumination at 25 and 65 °C, respectively.