Scaffold-Guided Crystallization of Oriented α-FAPbI₃ Nanowire Arrays for Solar Cells

Abstract

Perovskite nanowire arrays with large surface areas for efficient charge transfer and continuous highly crystalline domains for efficient charge transport exhibit ideal morphologies for solar-cell active layers. Here, we introduce a room temperature two-step method to grow dense, vertical nanowire arrays of formamidinium lead iodide (FAPbI 3 ). PbI 2 nanocrystals embedded in the cylindrical nanopores of anodized titanium dioxide scaffolds were converted to FAPbI 3 by immersion in a FAI solution for a period of 0.5–30 min. During immersion, FAPbI 3 crystals grew vertically from the scaffold surface as nanowires with diameters and densities determined by the underlying scaffold. The presence of butylammonium cations during nanowire growth stabilized the active α polymorph of FAPbI 3 , precluding the need for a thermal annealing step. Solar cells comprising α-FAPbI 3 nanowire arrays exhibited maximum solar conversion efficiencies of >14%. Short-circuit current densities of 22–23 mA cm –2 were achieved, on par with those recorded for the best-performing FAPbI 3 solar cells reported to date. Such large photocurrents are attributed to the single-crystalline, low-defect nature of the nanowires and increased interfacial area for photogenerated charge transfer compared with thin films.

Fabrication of [001]‐Oriented FAPbI3‐Based Photodetector With Excellent Air Stability Via Green Anti‐Solvent Additive Engineering

“…[26] Various methods to grow perovskite films with [001] preferential orientation have been demonstrated through additive engineering. [27][28][29][30] Additives with appropriate functional groups (e.g., carboxyl group (─COOH) and ammonium group (─NH 2 )) have the capacity to stabilize unbonded atoms on specific facets and modulate surface energy. [31,32] Lee et al reported that the addition of a precursor of 2D perovskite PEA 2 PbI 4 can induce growth in the [001] direction by controlling the surface energy of specific facets during the crystallization process.…”