P. Jayarama Reddy

Studies of ZnxCd1-xS films and ZnxCd1-xS/CuGaSe2 heterojunction solar cells

Thin film ZnxCd1-xS/CuGaSe2 heterojunction solar cells were prepared by laser evaporating CuGaSe2 onto sprayed ZnxCd1-xS films. The physical properties of ZnxCd1-xS films are discussed to study the influence of zinc content in the ZnxCd1-xS layer on the performance of the heterojunction. The photovoltaic properties of the cells were studied using illuminated current-voltage characteristics and spectral response measurements. The typical cell parameters obtained for a Zn0.5Cd0.5S/CuGaSe2 junction were Voc=710 mV, Jsc=11.8 mA cm-2, FF=0.50 with an efficiency of 4.9% on an active area of 1 cm2 without any antireflection coating.

Physical behaviour of CdO films prepared by activated reactive evaporation

High transparent and conductive CdO films were prepared using the activated reactive evaporation technique on Corning 7059 glass substrates. The film resistivity and transmittance were found to be influenced by the glow power of the discharge. Electron mobilities of 4-28 cm2 V-1 s-1 and carrier density in the range 7.8*1018-6.97*1019 cm-3 were observed. The energy gap of the films calculated from the optical absorption measurements was 2.42 eV.

Photovoltaic performance of p-AgInSe2/n-CdS thin film heterojunctions

Abstract Polycrystalline thin film p-AgInSe 2 /n-CdS heterojunctions were fabricated and current density–voltage, capacitance–voltage and spectral response of the junctions were studied. The heterojunction was illuminated in the back-wall configuration and an open-circuit voltage of 500 mV, a short-circuit current density of 24 mA cm −2 and an electrical conversion efficiency of 6% have been obtained for a cell 1 cm 2 in area under a solar input of 100 mW cm −2 .

Optical properties of spray deposited ZnO films

Abstract Transparent conducting ZnO films were deposited on Corning 7059 glass substrates by spray pyrolysis technique. The films showed high transparency around 0.5 μm, at which maximum solar radiation is obtained, and a high reflectance in the infrared region. The figure of merit was evaluated from the resistivity and transmittance data.

Preparation of ZnO films films by activated reactive evaporation

High quality films of zinc oxide were prepared by an activated reactive evaporation technique onto 7059 Corning glass substrates. Film resistivities of approximately 10-3 Omega cm and optical transparency of more than 88% in the wavelength range 300-800 nm were prepared by adjusting depositing parameters. The electron carrier densities in the range 2-12*1019 cm-3 and mobilities of 10-45 cm2 V-1 s-1 were observed. The energy gap of zinc oxide film was evaluated as 3.3 eV from optical absorption measurements.

Influence of oxygen partial pressure on the physical behaviour of CdO films prepared by activated reactive evaporation

Cadmium oxide thin films were prepared by evaporating cadmium in the presence of oxygen. The effects of varying the oxygen partial pressure on the physical properties were investigated. The films showed a cubic structure with (111) preferred orientation. All the films exhibited the n-type conductivity in the range of oxygen partial pressure used. The films evaporated under the optimum oxygen partial pressure of 1 × 10−3Torr exhibited a resistivity of 5.6 × 10−3Ω cm and a transmittance of about 90% in the visible region.

Structural and electrical properties of CdSexTe1−x thin films

The ternary semiconductors compounds are found to be very useful in the fabrication of thin film devices. This paper reports the preparation of CdSexTe1−x films (1 ⩾ x ⩾ 0) in the thickness range 1000–3000 A by vacuum evaporation technique onto glass and mica substrates held at temperatures, 303 to 623 K in a vacuum better than 5 × 10−6 torr. The films were characterised by determining their composition and structure. The structure of the films, examined using XRD and TEM techniques, was found to be cubic (zincblende) in the entire composition range. The electrical resistivity and Hall mobilities have been determined as a function of film composition and deposition temperature.

Characterization of thin film ZnCdS/CdTe solar cells

n-ZnCdS/p-CdTe polycrystalline thin film solar cells were fabricated by laser evaporating CdTe onto sprayed ZnCdS films. The cells were characterized by studying current-voltage, capacitance-voltage and spectral response measurements. A maximum efficiency of 7.6% was observed for a cell area of 1 cm2.

Characterization of p-AgGaSe2/n-CdS thin film heterojunction

Abstract AgGaSe 2 is a potential material for the preparation of Schottky diodes and solar cells. p-AgGaSe 2 /n-CdS heterojunctions were fabricated and the J - V , C - V and spectral response characteristics were studied. The typical cell parameters obtained were: V oc =510 mV, J sc = 13.8 mA/cm 2 , FF=0.55 and gh =4.5%.

Photoconductive response of polycrystalline n-AglnSe2 thin films

Abstract Photoconductivity response spectra of vacuum flash evaporated polycrystalline n-AglnSe 2 thin films are reported. The peak and shoulders observed in the photoconductivity spectra are attributed to transitions from valence sub-bands to the conduction band. From the room temperature spectra, the band gap energies, spin-orbit and crystal-field parameters are determined. The variation of photocurrent with applied bias voltage, illumination intensity and temperature are also studied.