Tungstate‐mediated In‐situ Passivation of Grain Boundary Grooves in Perovskite Solar Cells

Abstract

Possessed with advantageous optoelectronic properties, perovskites have boosted the rapid development of solution-processed solar cells. The performance of perovskite solar cells (PSCs) is significantly weakened by the carrier loss at grain boundary grooves (GBGs); however, it receives limited attention and there lacks effective approach to solve this issue. Herein, for the first time, we constructed the tungstate/perovskite heterointerface via a "two step" in situ reaction approach that provides effective defect passivation and ensures efficient carrier dynamics at the GBGs. The exposed perovskite at grain boundaries is converted to wideband-gap PbWO 4 via an in-situ reaction between Pb 2 + and tungstate ions, which passivate defects due to the strong ionic bonding. Moreover, recombination loss is further suppressed via the heterointerface energetics modification based on an additional transformation from PbWO 4 to CaWO 4 . PSCs based on this groove modification strategy showed good universality in both normal and inverted structure, with an improved efficiency of 23.25 % in the n-i-p device and 23.33 % in the p-i-n device. Stable power output of the modified device could maintain 91.7 % after around 1100 h, and the device efficiency could retain 92.5 % after aging in air for around 2110 h, and 93.1 % after aging at 85 °C in N 2 for 972 h.

Ionic Liquid Bridge Assisting Bifacial Defect Passivation for Efficient All-Inorganic Perovskite Cells with High Open-Circuit Voltage

“…From Figure 5e, the fitted slope can be determined by the formula V oc = n(k B T/q) ln (P light ) + C, where n is an ideal factor, C is a constant, k B is the Boltzmann constant, T is an absolute temperature, q is the elementary charge, and P light is light intensity. 62 The closer the fitted slope is to 1kTq −1 , the lower the amount of nonradiative recombination assisted by the trap states. Compared to the Control PSC (1.92kTq −1 ), the Target-1 PSC has a lower slope (1.22kTq −1 ), suggesting that BMIMAc modification significantly inhibits the trapassisted nonradiative recombination and facilitates to increase V oc .…”

“…Furthermore, evolutions of V oc and J sc versus light intensity ( P light ) are measured to investigate the carrier recombination kinetics of Control and Target-1 PSCs. From Figure e, the fitted slope can be determined by the formula V oc = n ( k B T / q ) ln ( P light ) + C , where n is an ideal factor, C is a constant, k B is the Boltzmann constant, T is an absolute temperature, q is the elementary charge, and P light is light intensity . The closer the fitted slope is to 1kT q –1 , the lower the amount of nonradiative recombination assisted by the trap states.…”

Synergistic Defect Passivation and Crystallization Modulation in Efficient Perovskite Solar Cells: The Case of Multifunctional 2-Anisidine-4-Sulfonic Acid

“…However, due to the soft ionic crystal nature of perovskite itself and its uncontrollable rapid crystallization in low-temperature solution fabrication process, , abundant adverse defects including uncoordinated Pb 2+ , cation vacancies and halide ionic defects will inevitably appear on the perovskite surface and grain boundaries (GBs), − thus irregular-aligned orientations of the perovskite crystal grains. Worse still, these defects sites as nonradiative recombination centers can not only provide pathways for external water and oxygen erosion, inducing the irreversible degradation of film and corresponding device, but also aggravate nonradiative recombination and ion migration, resulting in distinctly decreased open-circuit voltage ( V oc ) and fill factor (FF) …”

“…Worse still, these defects sites as nonradiative recombination centers can not only provide pathways for external water and oxygen erosion, inducing the irreversible degradation of film and corresponding device, but also aggravate nonradiative recombination and ion migration, resulting in distinctly decreased open-circuit voltage (V oc ) and fill factor (FF). 7 To adequately settle the above-mentioned problems, enormous efforts have been taken toward the development of various passivation materials to heal imperfections, modulate perovskite crystallization and improve the efficiency and stability of PSCs. 8−13 Additive engineering has been known as a feasible and effective method to passivate defect sites and directly regulate the morphology of perovskite for fabricating high-crystallinity, low-defect-density, large-size-grain perovskite film.…”

Selective grain boundary passivation by ammonium nitrate for enhanced performance and stability of FA-Cs based perovskite solar cells

“…Fan et al . 24 constructed a tungstate/perovskite heterointerface that provides effective defect passivation at the GBs. However, limited studies on GB passivation are conducted on MA-free PSCs (Table S1, ESI†), which are considered more promising because of their superior operational stability, although the efficiency could be slightly lower than that of MA-containing PSCs.…”