Self‐Formed Multifunctional Grain Boundary Passivation Layer Achieving 22.4% Efficient and Stable Perovskite Solar Cells

Abstract

The deep‐level defects at grain boundary (GB) result in serious trap‐assisted non‐radiative recombination. Moreover, the degradation of perovskite films is preferentially triggered by the attack of GBs by water and/or oxygen. Therefore, it is urgently needed to develop a multifunctional GB tailoring strategy to address the abovementioned issues. Herein, a self‐formed multifunctional GB passivation strategy is reported, where an ultrathin GB passivation layer is in situ constructed via incorporating K2SO4 into perovskite precursor solution. The self‐formed GB passivation layer plays multiple functions, including crystallization improvement, defect passivation, and moisture resistance. The GB manipulation strategy endows perovskite films reduced defect density, boosted carrier lifetime, and thus suppressed non‐radiative recombination, which contributes to efficiency enhancement from 20.39% to 22.40%. The GB tailoring approach makes the unencapsulated target device exhibit no degradation while the control device degrades to 93% of its initial power conversion efficiency after 1200 h ambient exposure with a relative humidity of 10–20%. The modified device maintains 98% of its original efficiency after aging at 60 °C for 1200 h, whereas only 89% for the control device. Herein, the importance of developing an in situ GB modification strategy in enhancing performance of perovskite photovoltaics is highlighted.

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

“…Currently, additive engineering is one of the effective methods commonly used for defect passivation in perovskite films. [ 12–14 ] Lewis acid molecules, [ 15,16 ] Lewis base molecules, [ 17–19 ] and organic/inorganic salts [ 20,21 ] have been introduced as additive to heal the defects at GBs and modulate the crystallization of perovskite films. Among them, the Lewis base additives incorporating N, O, and S electron donors is well known to reduce trap density and modulate crystallization of perovskite films.…”

“…[11] Currently, additive engineering is one of the effective methods commonly used for defect passivation in perovskite films. [12][13][14] Lewis acid molecules, [15,16] Lewis base molecules, [17][18][19] and organic/inorganic salts [20,21] have been introduced as additive toThe nonradiative recombination induced by trap states at the surface and grain boundaries impedes the further increase of power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Consequently, it is highly desirable to minimize the trap-assisted nonradiative recombination in perovskite films.…”

“…[11] Currently, additive engineering is one of the effective methods commonly used for defect passivation in perovskite films. [12][13][14] Lewis acid molecules, [15,16] Lewis base molecules, [17][18][19] and organic/inorganic salts [20,21] have been introduced as additive to…”

In situ lead oxysalt passivation layer for stable and efficient perovskite solar cells

“…As shown in Fig. 1b, after introducing Rb 2 SO 4 , the binding energy of the Pb 4f 7/2 (138.72 eV) and Pb 4f 5/2 (143.59 eV) states in the control perovskite films moved to 137.81 eV and 142.67 eV, 13 respectively. Meanwhile, compared with Rb 2 SO 4 , the binding energy of S 2p in the target perovskite films reduced from 168.70 eV to 162.80 eV (Fig.…”

“…This is mainly attributed to the improvement of the quality of the perovskite film and reduction of nonradiative recombination. In addition, the efficiency of the unencapsulated control device degraded to 70% of the initial efficiency after aging in air conditions with 15-20% relative humidity for 500 h, while the efficiency of the target device with the Rb 13 respectively. Meanwhile, compared with Rb 2 SO 4 , the binding energy of S 2p in the target perovskite films reduced from 168.70 eV to 162.80 eV (Fig.…”