Effect of porosity on the electrical and photoelectrical properties of textured n+ p silicon solar cells

Porous silicon layers (PSLs) were prepared by electrochemical etching with different etching current densities 10, 20 and 30 mA/cm2 on the front side of n+ p Si junctions. The formed porosity was determined gravimetrically within a good range of 88.27-97%. The effect of porosity on the structure, electrical, and photoelectrical properties was investigated. Scanning electron microscope (SEM) shows the evolution of PSLs morphology through the increase in surface area due to the regular increase in porosity. The optical reflectance measurements were obtained by using a UV-vis spectrophotometer equipped with an integrating sphere attachment, which reveals that the textured cells with PS layer structures have lower reflectivity value compared to the textured cell without PS structure. The current-voltage (I-V) characteristics of Al/PS/n+ p/Al junction fabricated at etching current density of 30 mA/cm2 were investigated and compared with the reference Al/n+ p/Al junction. The junction parameters such as series resistance (RS), ideality factor (n) and effective barrier height (ϕb) were determined by using different methods. Under illumination, the short-circuit current density (JSC) and the open-circuit voltage (VOC) increased from 0.35 mA/cm2 to 5.3 mA/cm2 and from 0.39 V to 0.62 V, respectively. The photosensitivity of PSLs solar cells showed a noticeable enhancement in quantum efficiency of the PS cells by increasing the porosity.