Evaporated Chalcopyrite Thin Films for Indoor Photovoltaic Applications

Abstract

The feasibility of capturing indoor artificial light using chalcopyrite photovoltaic absorbers has been analyzed. For this purpose, various chalcopyrite compounds (CuInSe2, CuInS2 and CuGaS2) were prepared by evaporation and then measured to obtain their main structural, morphological and optical characteristics. On the other hand, several artificial light sources were selected (incandescent, halogen, fluorescent, high-pressure sodium, metal halide and LED lamps) and represented by their respective spectral radiance. The absorption characteristics of CuInSe2 and CuInS2 are optimal for collecting light from fluorescent lamps and warm or cool white LEDs, requiring only a small film thickness of about 0.6 μm to capture 90-100% of the light radiance. Otherwise, the efficiency of CuGaS2 is found to increase as the color temperature of the LED lamp increases, being always lower and more dependent on the film thickness than for the other evaporated compounds. The worst performances (collection of less than 50% of the light radiance) correspond to incandescent and halogen lamps, which have a significant emission in the infrared region outside the absorption range of the evaporated chalcopyrite films. These results provide guidelines for the design of chalcopyrite-based photovoltaic devices suitable for operation under different indoor lighting conditions.

Luminous Transmittance and Color Rendering Characteristics of Evaporated Chalcopyrite Thin Films for Semitransparent Photovoltaics

“…The structural, morphological and optical properties of these films were analyzed in a previous work [23], where the surface morphology was examined via atomic force microscopy (AFM) with a Park XE-100, and the tetragonal chalcopyrite structure was iden-tified by means of X-ray diffraction (XRD) performed in a Philips X'pert instrument with radiation CuKα (λ = 1.54056 Å) and a Bragg-Brentano θ-2θ configuration. Figure 1a shows representative AFM images and Figure 1b displays the diffraction patterns corresponding to 600 nm thick films, where all the peaks are indexed according to the standard powder diffraction files for chalcopyrite CuInSe 2 (card file no.…”