Crown Ether Modulation Enables over 23% Efficient Formamidinium-Based Perovskite Solar Cells

Abstract

The use of molecular modulators to reduce the defect density at the surface and grain boundaries of perovskite materials has been demonstrated to be an effective approach to enhance the photovoltaic performance and device stability of perovskite solar cells. Herein, we employ crown ethers to modulate perovskite films, affording passivation of undercoordinated surface defects. This interaction has been elucidated by solid-state nuclear magnetic resonance and density functional theory calculations. The crown ether hosts induce the formation of host–guest complexes on the surface of the perovskite films, which reduces the concentration of surface electronic defects and suppresses nonradiative recombination by 40%, while minimizing moisture permeation. As a result, we achieved substantially improved photovoltaic performance with power conversion efficiencies exceeding 23%, accompanied by enhanced stability under ambient and operational conditions. This work opens a new avenue to improve the performance and stability of perovskite-based optoelectronic devices through supramolecular chemistry.

Interfaces in metal halide perovskites probed by solid-state NMR spectroscopy

“…In a more recent study by Su et al, a combined ssNMR and DFT modelling has been used to understand the passivation mechanism of surface uncoordinated lead sites by a crown ether (DB24C8). 382 The close proximity between MHP layers and the passivating agent (DB24C8) were elucidated by 2D 1 H- 207 Pb and 1 H-1 H correlation NMR. These results are corroborated by DFT modelling of DB24C8 passivated perovskite structures.…”

“…ssNMR has been used to study how a few of these salts, including choline, ethylammonium (EA), imidazolium, guanidinium (G) and tetrapropylammonium iodide (TPA), can passivate defects in MHPs. 375,[378][379][380][381][382] One important question presented by passivated MHPs is how the passivating agents incorporate within the device. Do the passivating salts mix microscopically with MHP grains, form a layer at the surface of the MHP lm, or segregate away from the MHP layer?…”

“…Nevertheless, 2D ssNMR spectroscopy has been applied to investigate the local proximities and interactions between MHP surfaces and passivating agents, and to elucidate the microscopic mechanisms of surface passivation. 375,378,379,381,382 Unlike the 2D 1 H-1 H DQ-SQ correlation experiment that probes through-space 1 H-1 H proximities within 5 A, the 2D 1 H-1 H SD experiment extends the length scale from sub-nanometer to several nanometers, and is thus well-suited to gain insight into intermolecular interactions and passivation mechanism in surface-modied MHPs.…”

Tailoring the Interface in FAPbI3 Planar Perovskite Solar Cells by Imidazole‐Graphene‐Quantum‐Dots

“…[ 28 ] In addition, the ideality factor could be evaluated by testing the dependence of V oc on the incident light intensity (Figure S21b, Supporting Information), which could reflect the trap‐assisted nonradiative recombination. [ 29 ] Here, the device with the SnO 2 /I‐GQDs ETL exhibits a slightly lower slope (1.21 kT / q ) than that with the SnO 2 ETL (1.64 kT / q ), which means the less trap‐assisted recombination, where k , T , and q are Boltzmann's constant, absolute temperature, and elementary charge, respectively. This result is in excellent agreement with the outcome showing the lowest trap density when the perovskite is deposited on SnO 2 /I‐GQDs.…”

A Cost‐Effective D‐A‐D Type Hole‐Transport Material Enabling 20% Efficiency Inverted Perovskite Solar Cells†

“…Typically, the n–i–p structures are fabricated with the n‐type TiO 2 or SnO 2 as the electron‐transporting materials (ETMs) and 2,2,7,7‐tetrakis( N , N ‐di‐ p ‐methoxyphenylamine)‐9,9‐spiro‐bifluorene (Spiro‐OMeTAD) as hole‐transport materials (HTMs). [ 5 ] Although most of the high efficiency was achieved by the n–i–p structures, such devices usually suffer from severe hysteresis. [ 6 ] Additionally, Li + dopants for improving the conductivity of Spiro‐OMeTAD bring adverse effects on device ambient stability.…”