Effect of (CH₃)₂Sn(COOH)₂ Electron Transport Layer Thickness on Device Performance in n-i-p Planar Heterojunction Perovskite Solar Cells

Abstract

The electron transport layer (ETL) plays an important role as a buffer layer in the efficient n-i-p planar heterojunction perovskite solar cells (PSCs). Recently, a new ETL, (CH3)2Sn­(COOH)2 (CSCO), with excellent conductivity and defect passivation of perovskites at the ETL/perovskite interface is synthesized by our group, which leads to a high-performance n-i-p PSC. Nevertheless, the effect of CSCO film thickness on the power conversion efficiency (PCE) of PSCs is unclear. In this work, we systematically explore the influence of CSCO film thickness on photovoltaic performance of Cs0.05FA0.81MA0.14PbI2.55Br0.45 (CsFAMA)-based PSCs. When the thickness of the CSCO film is less than 42 nm, the coverage of CSCO on an indium tin oxide (ITO) substrate becomes more complete as the CSCO film thickness increases, which reduces the leakage current and increases the charge-transfer efficiency at the CSCO/CsFAMA interface and therefore improves the PCE of the PSCs. However, for a thicker CSCO film with a thickness >42 nm, the ultraviolet–visible absorption intensity of CSCO increases, which is harmful to light absorption of the perovskite layer and therefore decreases the short-circuit current density of PSCs. Furthermore, a thicker CSCO film (>42 nm) leads to a sharply decreased shunt resistance, lowering the fill factor and open-circuit voltage. As a consequence, the maximum PCE of 20.42% is achieved by the PSCs based on the CSCO film with a thickness of 42 nm. In addition, the optimal PSC without encapsulation shows remarkable stability, retaining more than 85% of its initial conversion efficiency after 3000 h of storage in an ambient environment.

Defect Passivation with Metal Cations toward Efficient and Stable Perovskite Solar Cells Exceeding 22.7% Efficiency

“…Meanwhile, we also further improved the properties of the Cd 2+ -incorporated CsFAMA PSCs by using KCl to passivate the CSCO/perovskite interface. Under advantages of the double-passivation strategies, a device with the structure ITO/CSCO-KCl/CsFAMA:0.5%Cd 2+ /Spiro-OMeTAD/Au (denoted as device I) was fabricated, in which aqueous solution of KCl (an optimized concentration of 1 mg mL –1 based on our previous studies , ) was used to modify the interface between CSCO and the perovskite. The J–V curves of the optimized PSCs and the statistical distributions of the performance parameters with 15 devices are displayed in Figure a and Figure S6, and their photovoltaic performances are listed in Table S5.…”

“…Herein, based on our previous studies, , we incorporated Cd 2+ into the CsFAMA [the abbreviation of Cs 0.05 ((CH­(NH 2 ) 2 ) 0.85 (CH 3 NH 3 ) 0.15 ) 0.95 Pb­(I 0.85 Br 0.15 ) 3 ] perovskite layer to enhance the property and stability of its PSCs. We added different amounts of CdI 2 into CsFAMA perovskite precursor solution based on the molar ratio Pb 2+ and Cd 2+ ions.…”

Passivation mechanism of the perovskite upper interface based on MAPbBr3 quantum dots for efficient and stable perovskite solar cells

“…The highest V s of ∼860 mV is achieved at the concentration of 0.3 mM, indicating that most holes accumulate on the surface and the corresponding electrons are extracted by the electron transfer layer (ETL) at the optimum concentration of 0.3 mM, which is benecial for an enhancement of V oc of PSCs. [19][20][21][22][23] In addition, due to the coating of oleylamine (OLA) and oleyl acid on M-QDs, the surface defects of the perovskite lm are collectively passivated by the strong interaction between the hydrogen atoms of oleyl amine ligands and I of CFM, forming hydrogen bonds (N-H/I), as well as between the carboxyl group of oleyl acid ligands and the uncoordinated Pb 2+ of CFM, 13,[24][25][26] which is veried by Fourier transform infrared (FTIR) spectra in Fig. S3.…”

Enhanced efficiency and stability of Dion–Jacobson quasi-two-dimensional perovskite solar cells by additive

“…The reduced slope indicates that the solar cell with BMIMBF 4 has a lower trap density.Generally, carrier transport and recombination exercised a markedly impact on the performance of the device. The interface carrier density can be revealed by the Mott-Schottky (M-S) relation[42,43]. The capacitance-voltage characteristic and charge density are inversely proportional to the slope of the M-S plots.…”