Stabilizing α-Phase FAPbI₃ Perovskite Induced by an Ordered Solvated Quasi-Crystalline PbI₂

Abstract

In the two-step procedure for preparing a perovskite film, the chemistry of the PbI 2 solution plays an important role in determining the phase stability of perovskite films. We report here sulfoxonium salt-controlled crystallization for stabilizing α-phase formamidinium lead iodide (FAPbI 3 ) in perovskite solar cells via additive engineering of the PbI 2 solution. The in situ grazing incidence wide-angle X-ray scattering studies reveal that the trimethylsulfoxonium iodide (TMSOI) additive leads to an ordered solvated quasi-crystalline PbI 2 , which facilitates the transformation to α-phase FAPbI 3 at room temperature while reacting PbI 2 with FAI. As a result, the photovoltaic performance and stability of the perovskite solar cells are enhanced due to the improved optoelectronic properties of the perovskite films. A best-performing device shows a power conversion efficiency of 24.65% at one sun illumination. The unencapsulated devices stored at room temperature under 30−40% relative humidity maintain 96.40% of their initial efficiency after 1000 h.

Artificial Synapse Based on a δ-FAPbI3/Atomic-Layer-Deposited SnO2 Bilayer Memristor

“…The optical bandgaps ( E g ) of the δ-FAPbI 3 films and the ALD-SnO 2 layer are estimated to be 2.40 and 3.98 eV, respectively, from the absorbance data and Tauc plot (Figure S10a,b), which are quite consistent with the value reported elsewhere. , To further understand the detailed band alignment between δ-FAPbI 3 and ALD-SnO 2 , UPS was measured (Figure S10c,d) and analyzed according to the method reported elsewhere. − The estimated parameters are listed in Table S2, and the energy diagram of the δ-FAPbI 3 -based device without a SnO 2 layer is schematically illustrated in Figure c. The δ-FAPbI 3 has p-type characteristic and band bending by the Schottky junction with Ag, considering the work function of δ-FAPbI 3 is larger than that of Ag (4.3 eV) .…”

Polyfluorinated Organic Diammonium Induced Lead Iodide Arrangement for Efficient Two‐Step‐Processed Perovskite Solar Cells

“…[35] The increased grain size and reduced unreacted PbI 2 lead to fewer defects, which can improve the device performance of the corresponding PSCs by suppressing charge recombination. [36] Figure 3a shows XRD patterns of PVK and OFPP-PVK films. The peak intensity of PbI 2 is much lower than the peak of the perovskite phases in the OFPP-PVK film, while the opposite result was observed in PVK film, indicating that the discontinuous PbI 2 promotes the transformation of PbI 2 into perovskite crystallinity in OFPP-PVK film.…”

Defect Management and Ion Infiltration Barrier Enable High-Performance Perovskite Solar Cells

“…The contact potential difference (CPD) refers to the potential difference between the surface of the sample being tested and the probe, which denoted as CPD = W tip − W sample e , where W tip and W sample represent the work function (WF) of the tip and the sample, respectively . By subtracting the measured CPD value from the tip’s work function, the work function of the sample can be estimated. , As shown in the insets of Figure d–f, the line profile of the films indicates an increase of CPD values from 330 to 540 and then to 600 mV for the control, PHPA, and PHPA+PFOA film, respectively. The largest CPD value in PHPA+PFOA film delivers a smallest work function, which allows more efficient charge extraction efficiency in the corresponding device.…”