Suppressed Voltage Deficit and Degradation of Perovskite Solar Cells by Regulating the Mineralization of Lead Iodide

Abstract

efforts devoted to defect passivation, interface engineering, and optical engineering, the power conversion efficiency (PCE) of mixed cation metal halide perovskite solar cells (PSCs) with n-i-p architecture has been boosted to over 25%. [7][8][9] For polycrystalline perovskite films, defects that induce nonradiative recombination and unbalanced carrier transport limit the PCE of PSCs. [10][11][12][13][14] Moreover, negative defects with low formation energy provide pathways for ion migration and channels for oxygen and moisture invasion, thereby weakening the operational stability of PSCs. [15][16][17][18] Accordingly, diminishing the detrimental effects of the defects in perovskite film becomes particularly important for obtaining efficient and stable PSCs.The open-circuit voltage (V OC ) of PSCs was demonstrated to be highly dependent on the defect density of the perovskite film. Many studies have demonstrated that the formation of the PbI 2 phase in perovskite films can reduce the defect concentration and increase the V OC . However, excess PbI 2 may also generate voids and defects due to the photolysis of PbI 2 . The generated uncoordinated Pb 2+ is one of the dominant defects that cause V OC loss, as it provides nonradiative recombination sites to directly hinder carrier collection and cause energy loss Both the uncoordinated Pb 2+ and excess PbI 2 in perovskite film will create defects and perturb carrier collection, thus leading to the open-circuit voltage (V OC ) loss and inducing rapid performance degradation of perovskite solar cells (PSCs). Herein, an additive of 3-aminothiophene-2-carboxamide (3-AzTca) that contains amide and amino and features a large molecular size is introduced to improve the quality of perovskite film. The interplay of size effect and adequate bonding strength between 3-AzTca and uncoordinated Pb 2+ regulates the mineralization of PbI 2 and generates low-dimensional PbI 2 phase, thereby boosting the crystallization of perovskite. The decreased defect states result in suppressed nonradiative recombination and reduced V OC loss. The power conversion efficiency (PCE) of modified PSC is improved to 22.79% with a high V OC of 1.22 V. Moreover, the decomposition of PbI 2 and perovskite films is also retarded, yielding enhanced device stability. This study provides an effective method to minimize the concentration of uncoordinated Pb 2+ and improve the PCE and stability of PSCs.

Interfacial Energy Level Alignment and Defect Passivation by Using a Multifunctional Molecular for Efficient and Stable Perovskite Solar Cells

“…Tin oxide (SnO 2 ) is the most commonly used ETL in state-of-the-art PSCs due to its high electron mobility, high transmittance, high stability, great energy alignment, and low process temperature. [7][8][9] However, there are amounts of critical issues hidden in the interface between SnO 2 ETL and perovskite. For example, the defects distributed on the buried interface between perovskite and SnO 2 ETL can deteriorate PCE and the long-term stability of PSCs [10] such as oxygen vaccines, tin vacancies, and hydroxyl groups.…”

Multifunctional Trifluoroborate Additive for Simultaneous Carrier Dynamics Governance and Defects Passivation to Boost Efficiency and Stability of Inverted Perovskite Solar Cells

“…[10] It should be noted that the presence of non-radiative recombination sites in perovskite films and mismatched energy levels between the perovskite photoactive and transport layers act as obstacles for carrier collection and energy utilization, resulting in V oc loss. [11] However, the defects in perovskite films can produce trap-energy states within the band gap that trap charge carriers and promote the degradation of perovskite, [12] for example, by reacting with ambient moisture [13] or oxygen, [14] and facilitate ion migration. [15] In mixed-halide perovskites, defects are also associated with the commonly observed photo-stimulated halide phase segregation, which rapidly lowers the PCE under operating conditions.…”

Multifunctional Trifluoroborate Additive for Simultaneous Carrier Dynamics Governance and Defects Passivation to Boost Efficiency and Stability of Inverted Perovskite Solar Cells

“…These limiting factors can be mainly attributed to the open‐circuit voltage ( V oc ) loss and presence of crystallographic defects in perovskite films [10] . It should be noted that the presence of non‐radiative recombination sites in perovskite films and mismatched energy levels between the perovskite photoactive and transport layers act as obstacles for carrier collection and energy utilization, resulting in V oc loss [11] . However, the defects in perovskite films can produce trap‐energy states within the band gap that trap charge carriers and promote the degradation of perovskite, [12] for example, by reacting with ambient moisture [13] or oxygen, [14] and facilitate ion migration [15] .…”