Metal oxide coated p–n junction silicon electrodes for photoelectrochemical solar energy conversion

Abstract

This paper is dedicated lo Professor Camille Srrrzrlor/y 011 rlze occrrsiorr of his 65111 birrhrlayHIROsHl TSUBOMURA, YOSHIHIRO NAKATO, MASAHIRO HIRAMOTO, and HIROYUKI YANO. Can. J. Chem. 63, 1759Chem. 63, (1985. Photoelectrochemical propcrties of p-'-n junction silicon electrodes, abbreviatcd as p+n-Si, coated with thin oxide films of titanium, tungstcn, or iron have been investigated in aqueous solutions of hydrogen iodide and iodine. The films were deposited by electron-beam evaporation of the mctal oxide sinters. The photocurrent in a p'n-Si elcctrodc coated with TiO' increased dramatically when it was heatcd at temperatures highcr than 500°C, though the O/Ti atomic ratio as determined by ESCA analysis was unchanged. The fill factor of the photovoltaic cell composcd of this clcctrode, a platinum counter electrode and an aqueous solution of 7.6 M HI and 0.03 M 1' was improvcd by coating with ruthcnium or its oxide. Thc photovoltaic cell attained a high solar to electrical cnergy convcrsion efficiency of 9.3% (AMI), with an opcn circuit photovoltage of 0.58 V , a short circuit photocurrcnt of 26.6 mA cm-' and a fill factor of 0.61. The photocurrent was stable for 350 h. For the cases of electrodes coated with a FczO, or WO, film. high fill factors were obtained evcn without ruthenium coating. Thc effect of the nature of Si -metal oxide junctions, the donor density in the oxide, the relations between the flat band potential of the oxide and the redox potential of the solution, etc., on the conversion efficicncy was discussed.HlRos~l TSUBOMURA, YOSHIH~RO NAKATO, MASAHIRO HIRAMOTO et HIROYUKI YANO. Can. J . Chcm. 63, 1759 (1985). Optrant dans des solutions aqueuscs d'iodurc d'hydrogene et d'iode, on a CtudiC Ics proprittts phototlcctrochimiqucs d'tlectrodes de silicium, a jonction p+-n rcprksentCes par p 'n-SI, recouvertes dc minces couches d'oxydes dc titane, de tungstkne ou de fer. On a dtpost les films en faisant appel i I'dvaporation par faisceaux d'dlectrons dc frittages d'oxydes de mCtaux. Le courant photoClectrique de I'Clectrode p+n-Si sur laquelle on a dtposd du TiOl augmcnte d'une f a~o n dramatique lorsqu'on la chauffe i des temptraturcs suptrieurcs h 500°C; on obtient ce rCsultat meme si le rapport atomlque dc O/Ti, tcl que dCtermint par une analysc ESCA, dcmeure inchange. Le facteur de remplissage dc la cellule photovoltai'que composte de cette tlectrode, d'une contre-dlcctrode de platine et d'une solution aqueuse 7,6 M cn HI ct 0,03 M en I? augmente si I'on y dCposc du ruthCnium ou son oxyde On peut atteindre un haut dcgrd (9,3% AMI) d'cfficacitd pour la conversion de I'tnergie solaire en tncrgie Clcctrique SI I'on opkre avcc un photovoltage en circuit ouvcrt de 0,58 V , un photocourant dc court circuit de 26,6 m~c m -' et un facteur de rcmplissage dc 0,61. Le photocourant s'cst avdrd stable pour 350 h. Dans les cas des Clectrodes sur IesqueIles on a dCposC dcs films de FeZO, ou de WO,, on a pu obtenir des factcurs dc remplissage tlevds sans mCme dCposer du ruthenium. On discutc dc I'cffct de la n...

Si photoanode protected by a metal modified ITO layer with ultrathin NiOxfor solar water oxidation

“…In this method, two interfaces to separate the processes of the carrier generation at one (photoelectrical junction) and the chemical fuel formation at the other (electrochemical junction) are utilized to replace the single photoelectrochemical interface formed directly by the photoanode with or without a catalyst and the electrolyte. Materials include metals or metallic silicides, 5 wide band gap semiconductors (such as TiO 2 [6][7][8][9] , ZnO, 10 WO 3 , 11 GaN, 12 and Fe 2 O 3 13 ), transparent conducting oxides (TCO, such as mixtures of SnO 2 and In 2 O 3 , 14,15 SnO 2 16,17 and Sb/Ru-SnO 2 18,19 ), transition metal and its oxides polymers (PEDOT:PSS, 27 polyaniline, 28 polyacetylene, 29 and polypyrrole 30 ). Performances of the so-far developed materials or systems greatly depend on the properties of the coating and the two interfaces, such as the barrier height for charge separation, light absorption, photostability/electrochemical stability, hole conductivity, and OER catalytic activity.…”

Silicon protected with atomic layer deposited TiO2: conducting versus tunnelling through TiO2

“…Many researchers are now using materials such as TiO 2 to help protect photoabsorbers from oxidation or corrosion in photoelectrochemical reactions. [2][3][4][5][6] In some cases it has been proposed that electrons tunnel through TiO 2 , 2 while in other cases it has been shown that the electrons traverse classically through the conduction band. 4 While both of these methods allow the electron to be transferred through TiO 2 to an electrolyte, the conditions and limitations of each method vary greatly.…”

Thin-Film Materials for the Protection of Semiconducting Photoelectrodes in Solar-Fuel Generators

“…Islands of Pt particles were shown to protect n-Si photoanodes in a 4.8 M HBr / 0.03 M Br 2 electrolyte 130. In addition to metals and silicides, conductive oxide coatings such as ITO, SnO 2 , Sb-doped SnO 2 , TiO 2 , Fe 2 O 3 and WO3 have been shown to exhibit stable photoelectrochemical behavior in conjunction with n-Si photoanodes under halide oxidation conditions 76,[131][132][133][134]. Both ion-beam sputtered ITO on n-Si with a RuO 2 co-catalyst, and CVD-grown SnO 2 on n-Si with a Pt co-catalyst, have shown 20 h of stability in either a Cl 2 /Cl -electrolyte (pH = 6.6) or in a I 3 -/I -electrolyte (pH = 1.5), respectively 76.…”

“…Both ion-beam sputtered ITO on n-Si with a RuO 2 co-catalyst, and CVD-grown SnO 2 on n-Si with a Pt co-catalyst, have shown 20 h of stability in either a Cl 2 /Cl -electrolyte (pH = 6.6) or in a I 3 -/I -electrolyte (pH = 1.5), respectively 76. Yano et al134 reported that thin layers of electron-beam evaporated TiO 2 , Fe 2 O 3 or WO 3 stabilized np + -Si junctions for iodide oxidation, and a TiO 2 -stabilized buried junction np + -Si photoanode exhibited V oc = 580 mV and 330 h of stability for the oxidation of fuming HI.Boron-alloyed Si surfaces also have shown stability for halide oxidation. In one case, an np + -Si junction with a heavily B-enriched surface was formed by drop casting a saturated methanol solution of boron trioxide (BO 3 ) onto Si surfaces, followed by annealing at 1000 °C for 2 h in air 135.…”