High efficiency flexible perovskite solar cells using SnO2/graphene electron selective layer and silver nanowires electrode

Abstract

Ultrafine silver (Ag) nanowires dispersed in a mixed solution of EMIMBF4 and water were spin-coated onto polyethylene terephthalate as the flexible electrode of perovskite solar cells (PVSCs). The weakly oxidized graphene nanosheets (GNs) were incorporated into SnO2 (SnO2/GNs) to enhance the electron mobility and flexibility of the electron selective layer (ESL). The deposited C60-self-assembled monolayer (C60-SAM) between the ESL and the perovskite can inhibit charge recombination. Herein, the improved surface photovoltage responses can be attributed to the synergistic effect of C60-SAM and SnO2/GN ESL under zero and applied electric field. The best-performing PVSC has achieved a power conversion efficiency (PCE) of 13.36%, a Voc of 1.10 V, a Jsc of 18.39 mA cm−2, and a fill factor (FF) of 0.66 under a reverse voltage scan (the corresponding PCE of 12.81%, Voc of 1.10 V, Jsc of 18.19 mA cm−2, and FF of 0.64 under a forward voltage scan), indicating a negligible hysteresis. The EMIMBF4 can improve the dispersivity and intrinsic contacts between Ag nanowires. The C60-SAM will passivate the charge trap states of the perovskite, and the SnO2/GNs can promote electron transport. The PVSC from a low-temperature solution process is compatible with roll-to-roll manufacturing, and the intrinsic charge dynamics was also explored.

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

“…Tin oxide (SnO 2 ) is an ideal alternative for use as ETL in F-PSCs, due to its low-temperature compatibility, low-cost solution methods, desirable optoelectronic properties such as higher optical transparency, and enhanced device stability [14,90,91] [92][93][94][95][96][97][98]. To enhance electron transport and stability of SnO 2 based flexible PSCs, Zhou et al developed an approach to fabricate graphene quantum dot/SnO 2 composites (G@SnO2) as ETL [90].…”

“…An array of performance-improving strategies were also reported in the AgNW TCEs based F-PSCs. One such improvisation was the incorporation of graphene nanosheets into the SnO 2 electron transport layer for enhanced flexibility and improved charge transport and the usage of an EMIMBF 4 : water solution to disperse AgNWs [95]. The best PCE reported was 13.36% under a reverse voltage scan.…”

Recent Progress on Emerging Transparent Metallic Electrodes for Flexible Organic and Perovskite Photovoltaics

“…Besides protecting against chemical damage, another challenging task for designing bottom metal electrodes is the formation of good-quality perovskite films on top (especially for randomly aligned NWs), which are simultaneously influenced by the underlayer roughness and perovskite interface defects. [251,252] The surface roughness of the metal underlayer is critically important to the morphology and crystallinity of the perovskite. [248] To address this issue, it is worth noting that many of the aforementioned buffer layers can serve a dual function as planarization layers, flattening/smoothing the rough metallic surface for better film formation of the perovskite layer.…”

“…[ 253 ] Thus, an additional interface layer for passivating the defect states of the perovskite and inhibiting interface charge recombination, for example, a self‐assembly monolayer (SAM) of C 60 ‐SAM, can be added to the composite bottom electrode structure. [ 252 ] Recently, an ammonia:polyethylenimine‐modified PEDOT:PSS (PH1000 variant), named m‐FCE, was reported to effectively suppress the corrosion of Ag grid in flexible PSCs. By replacing the conductive PH1000, which is prone to cause an electrochemical corrosion of Ag, the already reduced m‐FCE layer enabled efficient flexible PSCs of 14.52% PCE using Ag grid bottom electrodes, which retained 86% of the initial PCE after 5000 bending cycles to a radius of 15 mm.…”

Recent progress of graphene‐based materials for efficient charge transfer and device performance stability in perovskite solar cells

“…Liu et al, 93 on the other hand, have fabricated flexible PSC devices and modified incorporation of weakly oxidized graphene nanosheets (GNs) as a dopant into SnO 2 (SnO 2 / GNs) as ETL and obtained PCE 13.36% with negligible hysteresis. Since the SnO 2 annealed with a low temperature in flexible PSC fabrication, the tendency to cause charge recombination at ETL/perovskite interface by electron transport obstruction is high due to the poor SnO 2 crystallinity.…”