Incorporating Lewis base polymers into a perovskite layer has been demonstrated as one of the most effective routes to passivate trap states at the grain boundaries, whereas the inferior electrical conductivity of polymers than that of perovskite would inevitably hinder charge transport across the perovskite grains. Herein, we reported a strategy of utilizing highly conductive graphene/Lewis base polymer (PM6 or PM7) composites as additives in perovskite, which simultaneously passivates the defects and facilitates charge transport in the film. We further revealed in the work that halogen elements (Cl/F) in the polymer (PM6/PM7) can p-dope the graphene and endow it with higher hole-transport selectivity, which is of critical importance as ambipolar charge transport without selectivity would induce significant charge recombination in graphene. By this design, we achieved an outstanding efficiency of 21.21%, which is significantly higher than that of the pristine device without treatment. The device also exhibited impressive stability by retaining 90% of its initial power conversion efficiency after 480 h aging in ambient air with a ∼35% relative humidity at room temperature.

The development of a hole transport layer (HTL) with persistent high conductivity, good moisture/oxygen barrier ability, and suitable passivation ability of perovskite defects is very important for achieving high power conversion efficiency (PCE) and long‐term stability of perovskite solar cells (PSCs). However, the state‐of‐the art HTL, lithium bis(trifluoromethanesulfonyl)‐imide (Li‐TFSI)‐doped 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD), does not have these abilities. Herein, the incorporation of antimony sulfide (Sb2S3) nanoparticles as a multifunctional additive into spiro‐OMeTAD is demonstrated. The Sb2S3 effectively improve the compactness of composite spiro‐OMeTAD:Sb2S3 HTL by inhibiting the Li‐TFSI aggregation and effectively prevent the infiltration of moisture and oxygen into the perovskite layer, resulting in its high chemical stability. More importantly, Sb2S3 not only improves the conductivity and hole mobility of the spiro‐OMeTAD:Sb2S3 through the oxidation of spiro‐OMeTAD by Sb2S3, but also makes the high conductivity more durable and stable in the atmospheric environment. In addition, Sb2S3 also effectively passivates the perovskite defects and accelerates the charge transfer from perovskite layer to HTL. As a consequence, the optimized PSCs based on spiro‐OMeTAD:Sb2S3 HTL exhibit a much higher PCE (22.13%) than that (19.29%) of the PSCs without Sb2S3 and show a greatly improved stability.

2,2′,7,7′-Tetrakis­(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD), the most widely used hole transport material in high-efficiency perovskite solar cells (PSCs), still has serious defects, such as moisture absorption and poor long-term conductivity, which seriously restrict further improvement of the power conversion efficiency (PCE) and stability of the cell. Herein, to overcome these problems, inorganic salt PbSO4(PbO)4 quantum dots (QDs) are incorporated into spiro-OMeTAD as the hole transport layer (HTL) for the first time. The incorporated PbSO4(PbO)4 QDs significantly hinder the agglomeration of lithium bis­(trifluoromethanesulfonyl)-imide and improve the long-term conductivity through the oxidative interaction between PbSO4(PbO)4 QDs and spiro-OMeTAD and hydrophobicity of the HTL. Furthermore, the spiro-OMeTAD:PbSO4(PbO)4 composite film can effectively passivate perovskite defects at the perovskite/HTL interface, resulting in suppressed interfacial recombination. As a result, the PSC based on the spiro-OMeTAD:PbSO4(PbO)4 HTL shows an improved PCE of 22.66%, which is much higher than that (18.89%) of the control device. PbSO4(PbO)4 also significantly improves the moisture stability for 50 days at room temperature (at RH ∼ 40–50%) without encapsulation. This work indicates that inorganic PbSO4(PbO)4 QDs are crucial materials that can be employed as an additive in spiro-OMeTAD to enhance the efficiency and stability of PSCs.

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%.

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.