Liesbeth Reijnen

Nanoporous TiO2/Cu1.8S heterojunctions for solar energy conversion

Thin films of p-type Cu 1.8 S have been deposited onto smooth and nanoporous n-type TiO 2 with Atomic Layer Chemical Vapor Deposition (AL-CVD). As precursors, Cu(thd) 2 and H 2 S have been used and self-limited deposition takes place between 125 and 240 °C. The crystalline phase and growth rate strongly depend on the process conditions; below 175 °C CuS and above this temperature, Cu 1.8 S is formed. Photospectroscopy shows that Cu 1.8 S has a bandgap of 1.75 eV and an absorption coefficient of 2.3 X 10 4 cm -1 at 500 nm. A 35-nm-thick Cu 1.8 S film on flat TiO 2 substrates shows a short circuit photocurrent of 30 μA/cm 2 and an open circuit photovoltage of 200 mV at broad-band irradiation of 2.8 kW/m 2 . The internal quantum efficiency is 6% at 500 nm.

CuInS2–TiO2 heterojunctions solar cells obtained by atomic layer deposition

Abstract Chalcopyrites are being studied widely as a promising absorber material for high-efficiency, low-cost, thin-film solar cells. The present paper deals with the growth of CuInS 2 thin films by atomic layer deposition. CuInS 2 films are grown on glass, F-doped SnO 2 coated glass, and TiO 2 thin films at a pressure of 2 mbar and in the temperature range of 350–500 °C using CuCl, InCl 3 and H 2 S as precursors. The influence of the process conditions on the structural and the electrical properties is examined. The growth temperature, the purge time and the vapor pressure of the precursors are found to be the decisive parameters. The composition of the thin films is investigated with X-ray diffraction and Raman spectroscopy. Depending on the process conditions single phase CuInS 2 or a mix of Cu x S, CuInS 2 and CuIn 5 S 8 are formed. The effect of annealing the CuInS 2 films in an H 2 S or O 2 atmosphere is studied as well.

Synthesis of pyrite (FeS2) thin films by low-pressure MOCVD

Thin films of iron disulfide have been prepared by low-pressure CVD (LPCVD) from iron(III) acetylacetonate (Fe(acac) 3 ), tert-butyldisulfide (TBDS), and hydrogen. The influence of the relevant CVD parameters on the growth rate, chemical composition (stoichiometry), morphology, crystalline phases, and contaminants has been examined. Pyrite thin films with a uniformity variation of less than 5 % over a length of 10 cm are obtained in a hot-wall LPCVD reactor. The present study shows that these films are deposited without detectable iron sulfide (FeS) phases at temperatures from 300 °C up to 340 °C on glass and silicon substrates. Growth rates vary between 0.2 nm min -1 and 12 nm min -1 . In all cases, the films are polycrystalline pyrite with an indirect bandgap of 0.95 ± 0.05 eV, and a dark specific resistance of 0.5-1.0 Ω cm. The absorption coefficient of the films is 3 ± 1 × 10 5 cm -1 at λ = 500 nm.

In situ mass spectrometric study of pyrite (FeS2) thin film deposition with metallorganic chemical vapor deposition

Pyrite, FeS{sub 2}, thin films have been prepared by metallorganic chemical vapor deposition using tert-butyl disulfide (TBDS) and iron(III) acetylacetonate [Fe(acac){sub 3}] as the precursors and H{sub 2} as co-reactant. The reaction mechanism is studied with in situ mass spectrometry. The thermal decomposition of TBDS and Fe(acac){sub 3} has been investigated, as well as the synthesis of FeS{sub 2}. A complicated gas-phase reaction chain occurs in the deposition reaction. In the first 1--2 cm of the deposition zone, thick rough films are formed, but further downstream in the reactor a smooth FeS{sub 2} film is deposited. This remarkable change in morphology is accounted for in the proposed reaction mechanism.

In-situ mass spectrometric study of the reaction mechanism in MOCVD of Pyrite (FeS2)

Pyrite, FeS 2 , thin films have been prepared by MOCVD using tert-butyldisulfide (TBDS), iron(III) acetylacetonate (Fe(acac) 3 ), and H 2 as the precursors. The reaction mechanism is studied by using in-situ mass spectrometry. The thermal decomposition of TBDS and Fe(acac) 3 has been investigated, as well as the synthesis of FeS 2 . A complicated gas-phase reaction chain occurs in the deposition reaction. In the first 1-2 cm of the deposition zone, a thick, rough film is formed, but further downstream in the reactor, a smooth FeS 2 film is obtained. This change in morphology is accounted for in the proposed reaction mechanism.