Fluorinated Graphene–Lewis-Base Polymer Composites as a Multifunctional Passivation Layer for High-Performance Perovskite Solar Cells

Abstract

Increasing the open-circuit voltage (V oc ) stands as a critical strategy for further improving the efficiency of organic−inorganic halide perovskite solar cells (PSCs). Lewis basic polymers, such as polymethyl methacrylate (PMMA), are considered as an effective approach to reduce the nonradiative recombination at the perovskite surface and protect the photoactive layer against moisture. However, the insulating nature of PMMA inherently leads to increased series resistance in PSCs. Here, we propose a multifunctional passivation layer (FG−PMMA) composed of fluorinated graphene (FG) and PMMA, offering high conductivity, a good passivation effect, and excellent hole transportation capabilities. The introduction of FG not only reduces the resistance of the PMMA layer but also improves its hydrophobicity. More importantly, we found that fluoride, which acts as a p-type dopant in graphene, can further reduce the nonradiative recombination centers by forming PbF 2 with uncoordinated Pb 0 at the perovskite/hole transport layer interface. As a result, the introduction of FG−PMMA significantly enhances the photovoltaic performance, with a record-high open-circuit voltage (V oc ) of 1.247 V and an average power conversion efficiency of 22.91%, higher than those of PMMA-based devices (20.75%, 1.210 V), as well as increasing the device's moisture stability, with over 90% of the initial efficiency maintained after 1200 h of aging at room temperature and a relative humidity of 35%.

Synergetic Optimization of Upper and Lower Surfaces of the SnO2 Electron Transport Layer for High-Performance n–i–p Perovskite Solar Cells

“…To evaluate reproducibility, the average efficiencies of 16 independent devices utilizing AlO x /SnO 2 -RbAc and SnO 2 -c are 21.15 and 20.12%, respectively, as shown in Figure d and Supporting Information (Figure S24). Mott–Schottky measurements were conducted to assess the internal junction properties of the device. , The built-in potentials for the AlO x /SnO 2 -RbAc and SnO 2 -c ETLs are 1.22 and 1.10 V, respectively, as shown in Figure e. A larger built-in field results in a more effective photogenerated carrier separation, aligning with the higher J SC and V OC in AlO x /SnO 2 -RbAc.…”

“…Mott−Schottky measurements were conducted to assess the internal junction properties of the device. 54,55 The built-in potentials for the AlO x /SnO 2 -RbAc and SnO 2 -c ETLs are 1.22 and 1.10 V, respectively, as shown in Figure 4e. A larger built-in field results in a more effective photogenerated carrier separation, aligning with the higher J SC and V OC in AlO x /SnO 2 -RbAc.…”

“…A larger built-in field results in a more effective photogenerated carrier separation, aligning with the higher J SC and V OC in AlO x /SnO 2 -RbAc. In addition, the devices can be further validated by plotting V OC as a function of light intensity, with n as an ideal factor related to defect-assisted recombination. , As illustrated in Figure f, the ideal factor is significantly lower for AlO x /SnO 2 -RbAc compared to that for SnO 2 -c (1.07 vs 1.78 kT / q ), suggesting a weakened trap-assisted recombination. The lower dark saturation current (9.7 × 10 –9 vs 3.4 × 10 –6 A), as shown in the Supporting Information (Figure S25), also indicates a lower trap density when the perovskite film is deposited on AlO x /SnO 2 -RbAc instead of SnO 2 -c. Additionally, electrochemical impedance spectroscopy (EIS) was conducted to measure the series resistance ( R s ) and the transport resistance ( R tr ) .…”

Fluorinated Polyimide Tunneling Layer for Efficient and Stable Perovskite Photovoltaics

“…[11] A negative vacuum level change can create potential wells, capturing carriers and leading to detrimental charge accumulation. Simultaneously, akin to the tunnel effect employed in tunnel oxide passivation contact (TOPCon) solar cells, [12,13] instead of elevating the series resistance in PSCs, [14,15] the introduction of a thin insulating layer at the perovskite/HTL interface facilitates the flow of charge carriers through potential barriers in the device structure. Among the numerous other strategies, including perovskite component engineering, [16,17] solvent engineering, [18] additive engineering, [20] and interface engineering, [21][22][23] this inserted thin insulating layer with an appropriate thickness can increase the open-circuit voltage (Voc) without significantly compromising the fill factor (FF).…”

Fluorinated Polyimide Tunneling Layer for Efficient and Stable Perovskite Photovoltaics

“…[11] A negative vacuum level change can create potential wells, capturing carriers and leading to detrimental charge accumulation. Simultaneously, akin to the tunnel effect employed in tunnel oxide passivation contact (TOPCon) solar cells, [12,13] instead of elevating the series resistance in PSCs, [14,15] the introduction of a thin insulating layer at the perovskite/HTL interface facilitates the flow of charge carriers through potential barriers in the device structure. Among the numerous other strategies, including perovskite component engineering, [16,17] solvent engineering, [18] additive engineering, [20] and interface engineering, [21][22][23] this inserted thin insulating layer with an appropriate thickness can increase the open-circuit voltage (Voc) without significantly compromising the fill factor (FF).…”