Oriented nucleation in formamidinium perovskite for photovoltaics

Abstract

Black-phase formamidinium lead iodide perovskite (FAPbI3), whilst the most promising species for efficient perovskite photovoltaics, is energetically unfavored at room temperature, and is thus always accompanied by undesirable yellow phases during crystallization 1,2,3,4 . The challenge to formulate the fast crystallization process of perovskite has limited the community in deriving unified guidelines for governing the formation of black-phase FAPbI3 5,6 . Here, through in-situ monitoring of the perovskite crystallization process, we report an oriented nucleation mechanism that acted as the key to avoid undesirable phases. This concept was applicable to improving the photovoltaic device performance under different film-processing scenarios. The small-area device demonstrated a power conversion efficiency of 25.4% (certified 25.0%), and the module (27.83 cm 2 ) achieved a champion aperture efficiency of 21.4% (certified). MainFormamidinium lead iodide perovskite (FAPbI3) features desirable bandgap and thermal resistance, and has thus emerged as the most promising candidate among the perovskite family for highly efficient photovoltaic devices 1,2,3,7,8 . However, the photoactive black-phase FAPbI3 is not energetically favorable at room temperature 4,9,10 .Polytype formation and other intermediate non-photoactive phases can readily occur, which undermines the photovoltaic performance. A few approaches have been developed to promote the formation of black-phase FAPbI3 at room temperature, such as adduct formation with PbI2 and solvent engineering using ionic liquids 11,12 .

Configuration Engineering of Unsymmetrical Structural Hole Transport Material for Efficient and Stable Regular/Inverted Perovskite Solar Cells

“…Solution-processable organic–inorganic hybrid perovskite solar cells (PSCs) have attracted extensive focus in the past decade due to their low-cost fabrication and remarkable photovoltaic performance. Until now, the highest power conversion efficiency (PCE) of PSCs has reached up to 26%, which is close to the theoretically calculated Shockley–Queisser limit efficiency (30.5%). – In general, PSCs can be divided into two kinds of typical device configurations including n–i–p regular configurations (r-PSCs) and p–i–n inverted ones (i-PSCs). The r-PSCs own good structural compatibility and energy level matching with perovskite layers and charge transport layers, so champion PCEs are always attained by the r-PSCs .…”

Synergistic Defect Passivation and Crystallization Modulation in Efficient Perovskite Solar Cells: The Case of Multifunctional 2-Anisidine-4-Sulfonic Acid

“…As a result, all of the modified perovskite films show extended τ avg (691.85, 1156.13, and 964.37 ns for the 0.05/0.1/0.2 mg mL –1 2A4SA-treated films, respectively) in comparison with the control film (530.19 ns). The enhanced PL intensity and extended carrier lifetime of the 2A4SA-modulated films indicate that there exist fewer nonradiative recombination sites . Note that the optimal concentration of 2A4SA is set at 0.1 mg mL –1 and then adopted in the following characterizations and analyses.…”

Additive Conformational Engineering To Improve the PbI2 Framework for Efficient and Stable Perovskite Solar Cells

“…Due to their exceptional optoelectronic properties, organic–inorganic hybrid perovskite solar cells (PSCs) have achieved substantial advancements in photovoltaic performance, especially in terms of efficiency and stability. − However, the power conversion efficiency (PCE) of PSCs is widely acknowledged to be dependent on the quality of the perovskite thin films. − Therefore, various methods, i.e., spin-coating (including one-step and two-step), , vapor-assisted solution processing, thermal evaporation, and pulse laser deposition, have been developed to obtain high-quality perovskite films with good optoelectronic performance. For example, the widely used one-step spin-coating deposition method requires meticulous control of the perovskite film’s crystallization .…”

“…The molecular structures of BU and DTBU are further confirmed by nuclear magnetic resonance hydrogen spectroscopy ( 1 HNMR) tests. 1 HNMR test results of BU are shown in Figure 1b, where the peaks around 8.5 and 6.8 ppm stand for R 2 NH and RNH 2 in BU, respectively. Additionally, their integration ratio is 1:4, where we can preliminarily conclude that the two primary amino (RNH 2 ) groups in BU are identical, indicating that BU molecules have a high degree of symmetry.…”