The Effect of the Alkyl Chains of the Alkylammonium Pesudohalide Additives on the Performance of Dion Jacobson Perovskite Solar Cells

Abstract

Dion‐Jacobson perovskite (DJP) films suffer from the high structural disorder and non‐compact morphology, leading to inefficient and unstable solar cells (SCs). Here, how the alkyl chains of alkylammonium pseudohalide additives including methylammonium thiocyanate (MASCN) and ethylammonium thiocyanate (EASCN), and propylammonium thiocyanate (PASCN), impact the microstructures, optoelectronic properties and the performance of the solar cells is investigated. These additives substantially improve the structural order and the morphology of the DJP films, yielding more efficient and stable solar cells than the control device. They behave quite differently in modifying the morphological features. Particularly, EASCN outstands the additives in terms of the superior morphology, which is compact and uniform and consists of the largest flaky grains. Consequently, the corresponding device delivers a power conversion efficiency (PCE) of 15.27% and maintains ≈86% of the initial PCE after aging in the air for 182 h. Conversely, MASCN as an additive produces uneven DJP film and the device maintains only 46% of the initial PCE. PASCN as an additive produces the finest grains in the DJP film, and the corresponding device yields a PCE of 11.95%. From the economical point of view, it costs 0.0025 yuan per device for the EASCN additive, allowing for cost‐effective perovskite solar cells.

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“…Similarly, the RP-BA has shown the fastest fall ( t f ≈ 386 ms) in the photocurrent compared to DJ-EDA ( t f ≈ 1090 ms) and RP-EA ( t f ≈ 1072 ms) when the illumination is turned off. The slow photoresponse time for DJ-EDA perovskites is attributed to the large mismatch between the conduction and valence bands of DJ perovskites and the work function of current collector FTO, which is possibly affecting the smooth extraction of photo charge carriers. , Additionally, the SEM images (Figure and Figure S4) of RP-EA perovskites have shown disk and star-shaped crystals with a preferential crystal growth along the substrate which favors the transport of charge carriers along the PbI 4 sheets, whereas the DJ-EDA perovskites formed the platelets and dot-shaped crystals; hence the charges may not follow any preferential transport direction. , …”

“…The variation in the photo response rise time (t r ) with n value for the RP-EA and DJ-EDA perovskites (n = 1−4) is shown in Figure S8c,d 51,52 Additionally, the SEM images (Figure 5 and Figure S4) of RP-EA perovskites have shown disk and star-shaped crystals with a preferential crystal growth along the substrate which favors the transport of charge carriers along the PbI 4 sheets, whereas the DJ-EDA perovskites formed the platelets and dot-shaped crystals; hence the charges may not follow any preferential transport direction. 53,54 The responsivity (R) and detectivity (D) are two important figures of merit for the photodetection. 55 Responsivity measures the optical to electrical conversion efficiency of a photodetector, expressed by the formula…”