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

Abstract

Numerous defects are present on the surface and at the grain boundaries of halide perovskite, which induce charge recombination and then impede the further enhancement of power conversion efficiency (PCE) and long-term stability of halide perovskite solar cells (PSCs). Consequently, it is highly desirable to decrease the defect density in order to improve the performance of PSCs. Here, we employ metal cations to passivate these defects by incorporating Cd2+ into the perovskite active layer. It is revealed that Cd2+ can not only adjust crystal growth but also reduce the defect density and restrain the charge recombination, which makes charge transfer more effective from perovskite layers to charge transport layers. Meanwhile, we mainly discuss the impact of the incorporated Cd2+ amount on the performance of CsFAMA perovskite films and devices. By controlling Cd2+ amount, a series of PSCs with good performance are obtained. A champion device is obtained at 0.5% Cd2+-incorporated amount with a high PCE of 21.95%. This device exhibits a good long-term stability with about 12% PCE loss after 42 days in an ambient environment with about 50% relative humidity at room temperature, while the control one loses about 17% of its initial efficiency under the same conditions. Furthermore, we improve the properties of the Cd2+-incorporated CsFAMA PSCs by using KCl to passivate the CSCO/perovskite interface, in which an optimized PCE is up to 22.75%.

Improved performance of perovskite solar cellsviacombining Pb–Sn alloying with the passivation effect of SnI2

“…In general, when S V exceeds 1 k B T / e , trap-assisted recombination is weak for perovskites if its value is close to 1 k B T / e . 35,43 From the above results, the slope of the excess SnI 2 treated devices is closer to 1 k B T / e , indicating that SnI 2 can effectively reduce trap-assisted recombination. Like with V OC , J SC has a god linear relationship ( S J represents the slope) with I as well, in which the ideal value of S J should be 1.…”

“…16 Moreover, the better crystallinity perovskite film contributes to the stronger light absorption. 35 From the above discussion, SnI 2 can improve the crystallinity of CsFAMA(Pb) perovskite, which is deemed as an another reason for the enhanced absorption.…”

A synergistic co-passivation strategy for high-performance perovskite solar cells with large open circuit voltage

“…6e), and the hole mobility (m h ) can be calculated by the Mott-Gurney law of J = (9/8)e r e 0 m h V 2 L À3 . 54 The m h of the TSTPtreated device (2.73 Â 10 À3 cm 2 V À1 S À1 ) is larger than that of the untreated one (1.29 Â 10 À3 cm 2 V À1 S À1 ), mainly due to the decreased trap density. The decreased n trap and enhanced m h in the TSTP-based device suggest that the TSTP strategy could efficiently passivate the defects of the perovskite layer, thus leading to the performance improvement of PSCs.…”

“…The n trap can be calculated according to the equation of n trap = 2 V TFL ε r ε 0 / eL 2 , where ε 0 and ε r represent the vacuum permittivity and relative dielectric constant of the perovskite layer, e is the elementary charge and L is the thickness of the perovskite layer (about 500 nm determined by cross-section SEM). 52–54 The n trap of the TSTP-treated device (2.70 × 10 15 cm −3 ) is lower than that of the untreated one (4.36 × 10 15 cm −3 ), indicating a decrease in the surface trap density after the TSTP treatment. Moreover, benefiting from the SCLC model at a high voltage, J 1/2 – V curves are analyzed (Fig.…”

Improved Efficiency and Stability of Perovskite Solar Cells Using the Multifunctional Additive Au Clusters

“…Generally, when S I exceeds 1k B T/e, the larger its value is, the severer the trap-assisted recombination is. 46,47 Compared with the control device, the Au cluster-modified cell has the slope closer to 1k B T/e, which indicates that the Au clusters can effectively suppress the trapassisted recombination because the defects of perovskite are passivated. The logarithms of J SC and I show a well linear relationship as well (S II represents the slope of this relationship), as depicted in Figure 6d.…”