Solution-Processed Nb:SnO₂ Electron Transport Layer for Efficient Planar Perovskite Solar Cells

Abstract

Electron transport layer (ETL), facilitating charge carrier separation and electron extraction, is a key component in planar perovskite solar cells (PSCs). We developed an effective ETL using low-temperature solution-processed Nb-doped SnO (Nb:SnO). Compared to the pristine SnO, the power conversion efficiency of PSCs based on Nb:SnO ETL is raised to 17.57% from 15.13%. The splendid performance is attributed to the excellent optical and electronic properties of the Nb:SnO material, such as smooth surface, high electron mobility, appropriate electrical conductivity, therefore making a better growth platform for a high quality perovskite absorber layer. Experimental analyses reveal that the Nb:SnO ETL significantly enhances the electron extraction and effectively suppresses charge recombination, leading to improved solar cell performance.

Rational design of SnO2-based electron transport layer in mesoscopic perovskite solar cells: more kinetically favorable than traditional double-layer architecture

“…Concerning materials, TiO 2 has been widely adopted in such duallayer structured ETL for M-PSCs so far [8,[12][13][14][15]. Actually, many attempts have been performed in order to make ETL kinetically more favorable, e.g., surface modifications, nanostructure tailoring, and the utilizations of alternative materials with better optoelectronic properties [16][17][18][19][20][21][22][23]. Compared with TiO 2 , SnO 2 is chemically stable as well and, more importantly, its charge mobility is almost two orders of magnitude higher than that of TiO 2 [11,24].…”

Tailoring electrical property of the low-temperature processed SnO2 for high-performance perovskite solar cells

“…2b, the peaks around 26.5°, 34.0°and 51.9°were corresponding to the (110), (101) and (211) diffraction planes of tetragonal rutile SnO 2 (JCPDS 21-1250), respectively [38]. With the doping of Nb 5+ , the peak slightly shifted to lower 2θ values, which indicated the lattice shrinkage due to the slightly larger radius of Nb 5+ compared to Sn 4+ [32]. Subsequently, the optical transmittance of the pristine SnO 2 and doped SnO 2 films was carefully studied since the light transmittance of the ETL could directly influence the light absorption of the top perovskite light absorber.…”

“…Herein, we for the first time doped Nb 5+ into the low-temperature SnO 2 sol-gel route (under 100°C) due to the close ionic radius of Nb 5+ to Sn 4+ , to tailor the electrical property of SnO 2 layers and the band alignment between SnO 2 and the normally used mixed perovskites for further improvement in charge injection and transport. It was previously reported that Nb-doping could be realized by adding niobium ethoxide or niobium chloride in the SnCl 2 ·2H 2 O solution, followed by a high annealing temperature (~190°C) for the crystallization of SnO 2 [32,33]. In our work, Nb-doped SnO 2 was crystallized with the refluxing (at 78°C) and aging process (at 40°C), and the temperature of the whole fabrication process was under 100°C, which would reduce the fabrication consumption and show potential application in the flexible devices.…”

Electron transport layer driven to improve the open-circuit voltage of CH3NH3PbI3 planar perovskite solar cells

“…Besides, the excitons, generated in perovskite layer, separate at the interface and diffuse directly to the ETL. Therefore, the ETL in N-I-P type planar structure is essential for the crystallization and morphology of perovskite films [15,16] and used to extract electrons [17][18][19]. Until now, TiO 2 is the most widely used ETL in perovskite solar cells [20][21][22]; however, ZnO has a higher carrier mobility, conductivity and a similar energy band profile with TiO 2 , ensuring a faster electron transport.…”