Influence of Two- and Three-Dimensional Engineering on the Trap State Distribution and Photophysical Properties of Lead Halide Perovskite Polycrystals

Abstract

Constructing a two-and three-dimensional (2D/3D) heterojunction structure on the surface of a 3D perovskite film, termed 2D/3D engineering, is effective in elevating the stability of perovskite polycrystal-based photovoltaic and photoelectronic devices; however, it remains controversial whether this protocol is favorable or detrimental to the device performance. Here, we prepare a series of 2D/ 3D perovskite films by post-treating the perovskite polycrystalline film with different concentrations of phenethylammonium iodide (PEAI). Systematic spectroscopy and electrochemical studies illustrate that PEAI can penetrate the 3D perovskite network and eliminate the intrinsic trap states of perovskite polycrystals, while the 2D perovskite nanosheets enriched on the top of the polycrystalline film may introduce additional trap states, which manipulate the photoluminescence performance and dynamics of the as-prepared perovskite films in an opposite manner. Based on this finding, the strategy of optimizing the photophysical properties of the host 3D perovskite through 2D/3D engineering is elaborated, paving the way for fabricating high-performance and high-stability perovskite polycrystalline films.

Blinking Carbon Dots as a Super-resolution Imaging Probe

“…Beyond a certain threshold voltage, once trap states become saturated, there is a sharp increase in current. 29,30 As shown in Figure 4a,b, initially both CDs show an increase in current until a certain threshold voltage (known as trap-filled limit voltage), followed by steep rise in current. The trap-filled limit voltage (V T ) obtained from the linear fitting of the current− voltage curve is calculated to be 1.18 and 1.4 V for green CDs and red CDs, respectively.…”

“…We have further carried out current–voltage and capacitance–voltage measurements to get vital insights on the trap state of red and green CDs , (Figure ) When an external voltage is applied to a particle film, the induced electric field drives charge carriers through the material. Initially, at lower applied voltages, the carriers are captured at these states as they pass through the material, which reduces the overall current.…”

Advances and challenges in molecular engineering of 2D/3D perovskite heterostructures

“…57 The extrinsic deep trap states generated during the formation of a 2D perovskite can exacerbate non-radiative charge recombination, which becomes a trade-off effect of a 2D perovskite. 58 Nevertheless, reducing the surface defects and eliminating non-radiation recombination at the surface is a widely accepted role of a 2D/3D heterojunction. However, the differences in passivation mechanism between heterojunctions and pure ammonium-functionalized organic cations are still unclear.…”