Highly Enhanced Efficiency of Planar Perovskite Solar Cells by an Electron Transport Layer Using Phytic Acid–Complexed SnO₂ Colloids

Abstract

SnO2 aqueous colloids as electron transport layers (ETLs) have been widely employed in planar perovskite solar cells (PSCs). However, the surface defects and energy level mismatch at the SnO2 ETL/perovskite interface are still great challenges for the power conversion efficiency (PCE) improvement. Herein, a natural and nontoxic phytic acid (PA) compound is introduced into the SnO2 aqueous colloids to prepare the ETL to depress its defects, and systematically study the influence of different PA complexation on the photovoltaic performance of PSCs. The results demonstrate that PA complexation can assemble unique coordination complexes between PA and SnO2 nanocrystals (NCs) in a new bonding of SnOP, which can passivate SnO2 inherent surface defects and tune the electronic properties of SnO2 ETLs. PA complexation can significantly disaggregate the SnO2 oligomers and reduce the cluster size distribution from 98.37 to 15.87 nm. Meanwhile, the reduction of surface trap states inhibits the potential barriers, thus the electrical conductivity is about two times as high as compared with the pristine SnO2 ETLs. Consequently, a high PCE of 21.43% in PA‐SnO2‐based PSCs is obtained, which presents an improvement of 10.9% over that of the pristine SnO2‐based PSCs.

Alkali Metal Cations Modulate the Energy Level of SnO2 via Micro-agglomerating and Anchoring for Perovskite Solar Cells

“…To explore the specific reasons of the improved performance, dynamic light scattering (DLS) is used to check the agglomeration of colloidal particles . As shown in Figure a–d, two Gaussian distributions for small-size (13 nm on average) and large-size (300.5 nm on average) agglomerates are observed in pristine SnO 2 dispersion.…”

“…The pH decreases when Na + is added, and the ionic interaction in dispersion is suitable to generate homogeneous tiny aggregates and destroy the large agglomerations (Figure e). The schematic illustration of the Na-Oxalate modification is shown in Figure f . Li + -doped suspension has the lowest alkaline and ionic interaction, generating large aggregates with particle sizes in micrometer.…”

Large improvement of photovoltaic performance of flexible perovskite solar cells using a multifunctional phospho-ethanolamine-modified SnO2 layer

“…By analyzing the proportion of O V in each sample, it is reasonable to believe that adding an appropriate amount of PE is beneficial for reducing the amount of O V . It is noteworthy that the new peak located at 530.94 eV in the XPS of the SnO 2 -PE film is assigned to Sn-O-P [29]. These results confirm that the phosphate group in the PE compound has a strong chemical interaction with the Sn dangling bond and forms a new coordinate bond Sn-O-P.…”

“…The peaks at 506 and 597 cm −1 related to Sn-O vibration in pristine SnO 2 shift to 524 and 609 cm −1 after PE modification [31]. Moreover, two new vibration peaks at 1090 and 1158 cm −1 in SnO 2 -PE are well assigned to the stretching mode of the PO 3 2− and PO 2 − groups [29]. Meanwhile, the Raman peak in the SnO 2 -PE sample is shifted to 783 cm −1 compared with that of the bare SnO 2 (777 cm −1 ) [32].…”

Multifunctional Thiophene-Based Interfacial Passivating Layer for High-Performance Perovskite Solar Cells

“…It clearly demonstrates the existence of TCA-Cl linked to the SnO 2 film, which could lead to an esterification reaction of −OH and −COOH, as shown in the schematic mechanism diagram (Figure a). Moreover, the peaks at 692.62 cm –1 observed of the pristine SnO 2 sample are related to Sn–O vibration . Compared with the SnO 2 sample, the characteristic peak of Sn–O vibration in the SnO 2 /TCA-Cl sample shifts to 671.65 cm –1 .…”