Decoupling Contributions of Charge‐Transport Interlayers to Light‐Induced Degradation of p‐i‐n Perovskite Solar Cells

Abstract

There is growing evidence that the stability of perovskite solar cells (PSCs) is strongly dependent on the interface chemistry between the absorber films and adjacent charge‐transport layers, whereas the exact mechanistic pathways remain poorly understood. Herein, a straightforward approach is presented for decoupling the degradation effects induced by the top fullerene‐based electron transport layer (ETL) and various bottom hole‐transport layer (HTL) materials assembled in p‐i‐n PSCs. It is shown that chemical interaction of MAPbI3 absorber with ETL comprised of the fullerene derivative most aggressively affects the device operational stability. However, washing away the degraded fullerene derivative and depositing fresh ETL leads to restoration of the initial photovoltaic performance when bottom perovskite/HTL interface is not degraded. Following this approach, it is possible to compare the photostability of stacks with various HTLs. It is shown that poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and NiOx induce significant degradation of the adjacent perovskite layer under light exposure, whereas poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA) provides the most stable perovskite/HTL interface. A time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) analysis allows identification of chemical origins of the interactions between MAPbI3 and HTLs. The proposed research methodology and the revealed degradation pathways should facilitate the development of efficient and stable PSCs.

Temperature‐ and Bias‐Dependent Degradation and Regeneration of Perovskite Solar Cells with Organic and Inorganic Hole Transport Layers

“…[28] The polymer PTAA may be more permeable than CuI to ion migration, such as the gradual movement of negative acceptors away from the PTAA or of positive ions into the PTAA. [29] Or, the increased vulnerability to ion migration may be due to a difference in the perovskite material itself because of its dependence on grain-size distribution [30] and crystalline quality, which can be affected by the underlying HTL. [31] Scanning electron microscope (SEM) images are shown in Figure 2, illustrating that the choice of PTAA for the HTL does change the crystallization process, resulting in rougher grains, although the grain size itself, on the order of 1 μm, was not significantly altered.…”

Configurable Organic Charge Carriers toward Stable Perovskite Photovoltaics

“…One possible pathway for such degradation is the HTM’s interactions with the perovskite decomposition products such as MAI and PbI 2 . For instance, by observing the changes in the distribution of Pb + and PbI + ions, it is found that light exposure leads to a depletion of PbI + signal near the interface between perovskite and HTM . This indicates that lead exists within the HTM in forms different from the lead iodide as it was prior to the light exposure.…”

Ultrathin PTAA interlayer in conjunction with azulene derivatives for the fabrication of inverted perovskite solar cells

“…Du et al, prepared a NiO x /PTAA bilayer that increased the PCE up to 17.1% 43 . Moreover, PTAA bilayers were formed in conjunction with reduced graphene oxide 44 ,graphene 45 , CuO x 46 , PFN-P2 47 , NiO x 48 and VO x 49 .…”