Boosting Perovskite Solar Cells Efficiency and Stability: Interfacial Passivation of Crosslinked Fullerene Eliminates the “Burn‐in” Decay

Abstract

Perovskite solar cells (PSCs) longevity is nowadays the bottleneck for their full commercial exploitation. Although lot of research is ongoing, the initial decay of the output power – an effect known as “burn‐in” degradation happening in the first 100 h – is still unavoidable, significantly reducing the overall performance (typically of >20%). In this paper, the origin of the “burn‐in” degradation in n‐i‐p type PSCs is demonstrated that is directly related to Li+ ions migration coming from the SnO2 electron transporting layer visualized by time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) measurements. To block the ion movement, a thin cross‐linked [6,6]‐phenyl‐C61‐butyric acid methyl ester layer on top of the SnO2 layer is introduced, resulting in Li+ immobilization. This results in the elimination of the “burn‐in” degradation, showing for the first time a zero “burn‐in” loss in the performances while boosting device power conversion efficiency to >22% for triple‐cation‐based PSCs and >24% for formamidinium‐based (FAPbI3) PSCs, proving the general validity of this approach and creating a new framework for the realization of stable PSCs devices.

24.96%‐Efficiency FACsPbI3 Perovskite Solar Cells Enabled by an Asymmetric 1,3‐Thiazole‐2,4‐Diammonium

“…[39] To unveil the effect of TDA-modification on the electronic properties of SnO 2 film, the electron mobilities of SnO 2 and SnO 2 /TDA films are evaluated by using the space chargelimited current (SCLC) method. [40] As shown in Figure 1g, the electron mobility is obviously increased from 6.49 × 10 −4 to 1.18 × 10 −3 cm 2 V −1 s −1 after TDA modification. In addition, the conductivity is tested (Figure 1h), [18] which is significantly enhanced from 2.42 × 10 −3 to 3.99 × 10 −3 mS cm −1 after TDA modification.…”

Breaking 1.7V open circuit voltage in large area transparent perovskite solar cells using bulk and interfaces passivation.

“…Conversely, the ISO and ISO-NEO devices retained more than 85% of the initial e ciency, with ISO exhibiting a slow, linear decreasing trend without any evidence of burn-in. The burn-in degradation is a common behavior in perovskite and organic solar cells, for which several mechanisms have been proposed 30,31 . In our case, the origin of the burn-in is likely to originate at the interface between PTAA and the perovskite, and the introduction of ISO represents a winning strategy in this regard.…”

A Multifunctional Molecular Bridging Layer for High Efficiency, Hysteresis‐Free, and Stable Perovskite Solar Cells

“…However, this issue is significantly inhibited for the passivated devices due to eliminated Li + ions migration, which is outside the scope of this paper and is discussed elsewhere. [ 27 ] Moreover, the air stability is also investigated and shown in Figure 5e. The unsealed FBA passivated device showed a noticeable increase in stability and retained more than 80% of the initial PCE after 1000 h, while the control device rapidly dropped to ≈50% of its initial value.…”

“…[25] Moreover, it could even pass through the perovskite layer and accumulate at the surface of the ETL, and higher Li-TFSi doping concentration could aggravate the hysteresis issue [26] and the "burn-in" effect. [27] recently, some researchers indicated that Li + ions migration is also an essential factor affecting the stability of PSCs at high temperatures. [28,29] At present, the methods to eliminate the migration of Li + ions include adding MoS 2 with flower-like microstructures into spiro-OMeTAD acting as a powerful sorbent for Li + ions; [30] doping reduced graphene oxide (rGO) to spiro-OMeTAD to provide adsorption sites for Li + ions [31] and using a "cross-linkable" PCBM derivative to blocks this migration of Li + ions.…”