Several Triazine-Based Small Molecules Assisted in the Preparation of High-Performance and Stable Perovskite Solar Cells by Trap Passivation and Heterojunction Engineering

Abstract

The functional group is the main body in modifying the perovskite film, and different functional groups lead to different modification effects. Here, several conjugated triazine-based small molecules such as melamine (Cy-NH2), cyanuric acid (Cy-OH), cyanuric fluoride (Cy-F), cyanuric chloride (Cy-Cl), and thiocyanuric acid (Cy-SH) are used to modify perovskite films by mixing in antisolvent. The crystallizations of perovskites are optimized by these molecules, and the perovskite films with low trap density are obtained by forming Lewis adducts with these molecules (Pb2+ and electron-donating groups including −NH2, CN–, and CO; I– and electron-withdrawing groups including F, Cl, N–H, and O–H). Especially for the Cy-F and Cy-Cl, the heterojunction structure is formed in the perovskite layer by p-type modification, which is conducive to charge transfer and collection in PSCs. Compared with that of control devices, the performance of devices with trap passivation and heterojunction engineering is obviously improved from 18.49 to 20.71% for MAPbI3 and 19.27 to 21.11% for FA0.85Cs0.15PbI3. Notably, the excellent moisture (retaining 67%, RH: 50% for 20 days) and thermal (retaining 64%, 85 °C for 72 h) stability of PSCs are obtained by a kind of second modification (Cy-F/Cy-SH)spin-coating a few Cy-SH on the Cy-F-modified perovskite film surface. It also reduces Pb pollution because Cy-SH is a highly potent chelating agent. Therefore, this work also provides an effective method to obtain high-performance, stable, and low-lead pollution PSCs, combining trap passivation, heterojunction engineering, and surface treatment.

Grain Boundary Chemical Anchoring via Bidirectional Active Site Additive Enables Efficient and Stable Perovskite Solar Cells

“…[22][23][24][25] The additive molecules containing CO have been widely demonstrated to control perovskite crystal growth and passivate film defects through the coordination interaction between the electron donor atom and undercoordinated Pb 2+ . [26][27][28] Notably, the strong coordination between additive molecules and uncoordinated Pb 2+ not only passivates defects, but also serves as anchor to strengthen the bonding force between grains, thereby further improving the stability of films. [19,29] Therefore, if multi-active-site ligand molecules could coordinate with different grains, it would exhibit a greater defect passivation potential.…”

In situ formation of Imidazole‐Based 2D interlayer for efficient perovskite solar cells and modules

“…Several efforts to improve the performance of perovskite cells have been carried out, but surface engineering has played a very critical role in leading these results. In particular, forming a thin heterogeneous passivation layer on the surface shows multifunctional effects such as reducing surface defects, optimizing interfacial energy levels, interfacial bridge, and forming an external protective layer 5‐11 . The formation of 2D perovskite is one of several good passivation methods, and more recently, phenethylammonium iodide (PEAI) has been applied to the surface of perovskite as the most promising surface engineered candidates 5,12,13 .…”

“…In particular, forming a thin heterogeneous passivation layer on the surface shows multifunctional effects such as reducing surface defects, optimizing interfacial energy levels, interfacial bridge, and forming an external protective layer. [5][6][7][8][9][10][11] The formation of 2D perovskite is one of several good passivation methods, and more recently, phenethylammonium iodide (PEAI) has been applied to the surface of perovskite as the most promising surface engineered candidates. 5,12,13 The PEAI passivation layer containing π-conjugated benzene moieties is transformed into the 2D perovskite, exhibiting the enhanced charge transport as well as the reduced neutral defects, led to efficiency improvement in the small-area unit cells.…”

Dual-layer synergetic optimization of high-efficiency planar perovskite solar cells using nitrogen-rich nitrogen carbide as an additive

“…2g and h display the corresponding I-V curves, in which the trap-lled limit voltage (V TFL ) can be derived from the kink point between ohmic linearity and space current nonlinearity. 32,33 The trap-state density is resolved vis a vis V TFL according to the following formula: V TFL ¼ eN trap L 2 /(233 0 ), where L and e are the thickness of the lm (30 nm) and the elementary charge, respectively. 3 0 and 3 are the vacuum permittivity and the relative dielectric constant.…”