Yolk-shell SnO2@TiO2 nanospheres as electron transport layer in mesoscopic perovskite solar cell

• Published in: Journal of sol-gel science and technology 2020-06, Vol.94 (3), p.731-742
• Main Authors: Mohammadbeigi, Arezoo, Mozaffari, Samaneh, Ghorashi, Seyed Mohamad Bagher
• Format: Article
• Language: English
• Subjects: Absorption spectra; Ceramics; Charge transport; Chemistry and Materials Science; Circuits; Composites; Conduction bands; Conversion; Current density; Electrochemical impedance spectroscopy; Electron transport; Energy bands; Energy gap; Glass; High resistance; Hysteresis; Inorganic Chemistry; Materials Science; Moisture resistance; Nanoparticles; Nanospheres; Nanotechnology; Natural Materials; Open circuit voltage; Optical and Electronic Materials; Original Paper: Sol-gel and hybrid materials for optical; Perovskites; Photoluminescence; photonic and optoelectronic applications; Photons; Photovoltaic cells; Short circuit currents; Solar cells; Spectrum analysis; Stability tests; Surface defects; Synthesis
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-020-05221-2

SnO 2 nanoparticles were synthesized and modified by TiO 2 shell through sol–gel method. Band gap energy and photoluminescence properties of SnO 2 nanoparticles and yolk-shell SnO 2 @TiO 2 nanospheres were investigated by UV–Vis absorption spectra and photoluminescence (PL) spectroscopy. The nanoparticles were used as electron transport layers (ETLs) for fabrication of perovskite solar cells (PSCs) and PSC based on yolk-shell SnO 2 @TiO 2 ETL showed higher photon conversion efficiency (PCE = 11.28%) and lower hysteresis index (37%) compared with the PSC made of SnO 2 ETL (PCE = 8.55% and hysteresis index = 52%). The increase in the short-circuit current density ( J sc ), open circuit voltage ( V oc ), and subsequently PCE for the PSC based on yolk-shell SnO 2 @TiO 2 ETL is attributed to the smoothness and uniformity of perovskite film, improvement of surface defects at the ETL/perovskite interface, and suitable energy band alignment for effective injection of electron from perovskite to the conduction band of TiO 2 as well as from TiO 2 to the SnO 2 . Electrochemical impedance spectroscopy (EIS) was employed to determine the charge transport resistance at the ETL/perovskite interface and confirmed the results obtained by the characteristic curve of the current density–voltage. The stability test of the devices displayed that long-term stability of PSC made of yolk-shell SnO 2 @TiO 2 ETL is almost the same as the SnO 2 ETL-based PSC because of the high resistance of SnO 2 against the moisture and oxygen in the environment. Highlights Yolk-shell SnO 2 @TiO 2 nanospheres and SnO 2 nanoparticles were synthesized using sol–gel method. Band gap energy and photoluminescence (PL) properties of nanoparticles were analyzed by UV–Vis absorption spectra and PL spectroscopy. Nanoparticles were applied as an electron transport layer (ETL) in the fabrication of perovskite solar cell (PSC). Photon conversion efficiencies of 11.28 and 8.55% obtained for PSCs with different ETLs based on yolk-shell SnO 2 @TiO 2 nanospheres and SnO 2 nanoparticles, respectively. Durability test of devices with different ETLs exhibited desirable long-term stability for PSCs after 1656 h (69 days).