Suppressing Interfacial Shunt Loss via Functional Polymer for Performance Improvement of Lead‐Free Cs₂AgBiBr₆ Double Perovskite Solar Cells

Abstract

All‐inorganic lead‐free Cs2AgBiBr6 double perovskite solar cells (PSCs) have attracted growing attention owing to their eco‐friendly features and robust intrinsic stability. However, arising from the rapid crystal growth, the poor film quality always leads to substantial non‐radiative recombination and inferior performance improvement. Herein, high‐efficiency and stable Cs2AgBiBr6 PSCs are obtained by introducing a functional polymethyl methacrylate (PMMA) layer at the perovskite surface to avoid direct contact between carbon and the underlying charge transfer layer, as well as to passivate the defects. When assembling into solar cells, the non‐radiative charge recombination is suppressed and the interfacial charge extraction is accelerated. As a result, the carbon‐electrode‐based Cs2AgBiBr6 PSC yields an enhanced efficiency of 2.25% with a high open‐circuit voltage of 1.18 V. Moreover, the unencapsulated device exhibits superior long‐term stability owing to the protection of the PMMA layer from corrosion by the extraneous water and oxygen, retaining nearly 100% of the initial efficiency after storage in 25 °C, with 5% relative humidity (RH) for 80 days and high temperature of 85 °C, and 0% RH for 60 days, respectively. A simple method of polymer passivation for enhancing the performance and stability of Pb‐free Cs2AgBiBr6 PSCs is provided.

High Open‐Circuit Voltage Cs2AgBiBr6 Carbon‐Based Perovskite Solar Cells via Green Processing of Ultrasonic Spray‐Coated Carbon Electrodes from Waste Tire Sources

“…achieved a PCE of 1.77 % and a 1.119 V V OC for pristine Cs 2 AgBiBr 6 , which could be further improved to 2.57 % and 1.177 V by doping the perovskite with small amounts of Li + [40] . Later, the same authors found that the addition of a thin passivating layer of PMMA enhances the PSC performances of pristine Cs 2 AgBiBr 6 (2.25 %, 1.180 V) [41] . Finally, Shao and co‐workers have improved the PCE and V OC of Cs 2 AgBiBr 6 ‐based C‐PSCs from 1.73 % and 1.13 V to 2.22 % and 1.20 V, respectively, by introducing 1‐butyl‐1‐methylpyrrolidinium chloride (BMPyrCl) into the perovskite structure to pin bromide ions, thus inhibiting their migration towards the interface with the CE [45] .…”

“…[42] All these approaches aimed at improving the energy level alignment at the perovskite/HTM interface, which emphasizes its crucial role for boosting the V OC . The V OC of PSCs that are based on unmodified Cs 2 AgBiBr 6 has been mostly lower than 1.1 V [9,42,43] and has only surpassed this value when Cu 2 O was applied as an HTM [39] or when CEs were used, [40,41] as it could also be observed for lead-based PSCs. [44] C-PSCs based on the DP have yet been reported only three times: originally, Li et al achieved a PCE of 1.77 % and a 1.119 V V OC for pristine Cs 2 AgBiBr 6 , which could be further improved to 2.57 % and 1.177 V by doping the perovskite with small amounts of Li + .…”

“…[35][36][37] Although the indirect bandgap of Cs 2 AgBiBr 6 is reported as 2-2.2 eV, [28][29][30] PSCs based on this material have been characterized by open-circuit voltages (V OC ) that, to the best of our knowledge, are close to or, in one single case, equal to the 1.2 V threshold. [38] Furthermore, those high values could only be achieved when the DP itself or some interfaces within the device were modified by, for example, substituting the organic HTM with an inorganic CuO 2 layer (1.198 V), [39] doping the perovskite with Li + (1.177 V), [40] making use of polymethyl methacrylate (PMMA) as a passivating capping layer between perovskite and a CE (1.180 V), [41] or by capping the perovskite layer with a 2D/3D mixed perovskite phase (1.18 V). [42] All these approaches aimed at improving the energy level alignment at the perovskite/HTM interface, which emphasizes its crucial role for boosting the V OC .…”

Novel Ag-based thin film solar cells: concept, materials, and challenges

“…However, the reason that limits the further improvement of CZTSSe device efficiency is the poor film quality, and the rapid crystal growth leads to substantial non-radiative recombination. Li et al 91 obtained high-quality Cs 2 AgBiBr 6 double perovskite solar cells by introducing a functional polymethylmethacrylate interfacial layer on the absorber layer surface to avoid direct contact between the electron transport layer and carbon layer. Defect reduction implies that the interface recombination-induced energy losses is effectively suppressed within the device, improving the charge transport process within the interface, which will thus be beneficial to increase the device efficiency to 2.05% with a high open-circuit voltage of 1.18 V.…”

Investigating the potential of lead‐free double perovskite Cs 2 AgBiBr 6 material for solar cell applications: A theoretical study

“…As a result, the final optimized device exhibited the superior PCE of 2.84% with improved stability under ambient atmospheric conditions. 21 Besides, Li et al introduced functional polymethyl methacrylate (PMMA) layer on perovskite absorber to suppress the defects and non-radiative recombination which resulted improved PCE of device up to 2.25% with very high V OC of 1.18 V. 22 Savory et al performed the first principle calculation study to evaluate chemical bonding, cation-anti site disorder and physical properties of Cs 2 AgBiX 6 (X = Cl, Br). They have stated the limited device conversion efficiency up to less than 10% for Cs 2 AgBiCl 6 and Cs 2 AgBiBr 6 based lead-free PSCs.…”