Characterization of Wavelength Effect on Photovoltaic Property of Poly-Si Solar Cell Using Photoconductive Atomic Force Microscopy (PC-AFM)

Abstract

We investigated the effect of light intensity and wavelength of a solar cell device by using photoconductive atomic force microscopy (PC-AFM). The <TEX>$POCl_3$</TEX> diffusion doping process was used to produce a p-n junction solar cell device based on a Poly-Si wafer and the electrical properties of prepared solar cells were measured using a solar cell simulator system. The measured open circuit voltage (<TEX>$V_{oc}$</TEX>) is 0.59 V and the short circuit current (<TEX>$I_{sc}$</TEX>) is 48.5 mA. Also, the values of the fill factors and efficiencies of the devices are 0.7% and approximately 13.6%, respectively. In addition, PC-AFM, a recent notable method for nano-scale characterization of photovoltaic elements, was used for direct measurements of photoelectric characteristics in local instead of large areas. The effects of changes in the intensity and wavelength of light shining on the element on the photoelectric characteristics were observed. Results obtained through PC-AFM were compared with the electric/optical characteristics data obtained through a solar simulator. The voltage (<TEX>$V_{PC-AFM}$</TEX>) at which the current was 0 A in the I-V characteristic curves increased sharply up to 1.8 <TEX>$mW/cm^2$</TEX>, peaking and slowly falling as light intensity increased. Here, <TEX>$V_{PC-AFM}$</TEX> at 1.8 <TEX>$mW/cm^2$</TEX> was 0.29 V, which corresponds to 59% of the average <TEX>$V_{oc}$</TEX> value, as measured with the solar simulator. Also, while light wavelength was increased from 300 nm to 1,100 nm, the external quantum efficiency (EQE) and results from PC-AFM showed similar trends at the macro scale, but returned different results in several sections, indicating the need for detailed analysis and improvement in the future.