Reducing the Surface Reactivity of Alkyl Ammonium Passivation Molecules Enables Highly Efficient Perovskite Solar Cells

Abstract

The non‐radiative recombination at the interfaces of perovskite solar cells (PSCs) is a crucial issue that limits the efficiency and stability of the devices. State‐of‐the‐art surface passivation strategies usually utilize alkyl ammonium halides to suppress the non‐radiative recombination of PSCs, but their high surface reactivity leads to the transformation into 2D perovskites under working conditions, limiting the passivation effect and the charge transport of PSCs. Herein, a non‐halide ionic salt 1‐naphthylmethylammonium formate (NMACOOH) is synthesized for surface passivation of perovskite films. In contrast to the traditional 1‐naphthylmethylammonium iodide, NMACOOH treatment hinders the formation of 2D perovskite and forms a thermally stable PbI2‐NMACOOH adduct on the perovskite surface. Surface characterization reveals that NMA+ can passivate the cation vacancies of the 3D perovskite while HCOO− passivates the metallic Pb0 and halide‐vacancy defects. Therefore, the non‐radiative recombination of PSCs is dramatically suppressed and a high open‐circuit voltage of 1.19 V is obtained. Finally, PSCs with high efficiency of 24.75% and improved long‐term stability (98% of the initial efficiency after 1800‐h storage) are obtained. Moreover, the NMACOOH‐passivated devices also show robust operational stability, retaining 83% of the initial efficiency after working for 658 h under continuous one‐sun illumination.

Ionic Liquid Modified Polymer Intermediate Layer for Improved Charge Extraction toward Efficient and Stable Perovskite/Silicon Tandem Solar Cells

“…N t of control, PMMA‐ and PMMA+IL‐treated devices are calculated to be 3.32 × 10 15 , 2.84 × 10 15 and 2.08 × 10 15 cm −3 respectively, proving that the introduction of ILs is able to collaborate with polymer in passivating more defects concurrently. [ 45 ] The reduction of defect concentration is also certified by light density versus V OC studies (Figure S5, Supporting Information), where the deduced diode ideal factor dropped from 2.72 to 2.19 when PMMA+IL passivation was introduced. The reduction in defect sites inhibited Shockley‐Read‐Hall recombination and led to improvements in V OC .…”

Ionic liquid-regulated PbI2 layers and defect passivation for efficient perovskite solar cells

“…n trap is calculated using the threshold voltage ( V TFL ) at the point of the Ohmic and TFL regions following the equation:where ε 0 is the vacuum permittivity, ε is the relative permittivity, e is the elementary charge, and L is the thickness of the perovskite film. 34 The V TFL of the control device was 0.479 V (Fig. 4a), while the V TFL of the FAAc-modified device was significantly reduced to 0.131 V (Fig.…”

Large-area all-perovskite-based coplanar photoelectrodes for scaled-up solar hydrogen production

“…3(c)). 45–49 It is speculated that CHA + acts as a Lewis base, donating electrons to Lewis acid ( i.e. , undercoordinated Pb 2+ ).…”