Abstract
Reducing the thickness of crystalline silicon solar cells is a crucial strategy for decreasing manufacturing costs and increasing mechanical flexibility. However, thinning the substrate fundamentally alters the optical and electrical behavior of the device. This study presents the analysis of the inherent trade-offs between optical absorption and internal carrier recombination in ultra-thin p-type silicon solar cells. To physically demonstrate these optical changes, standard n-type c-Si wafers were progressively thinned down by alkaline chemical etching achieving ultra-thin substrates of 70 μm, 50 μm, and 26 μm. A visual, rapid-assessment procedure utilizing a broad-spectrum white light source confirmed the filtering effect, demonstrating high transparency to red wavelengths at ultra-thinness. Reducing the cell thickness from the 150 μm to a 70 μm the effective absorption is limit to 955 nm. This leads to a loss in the absorption of higher-energy infrared photons, directly causing a drop in Jsc. Conversely, simulations reveal that this reduction in bulk silicon volume significantly decreases internal carrier recombination thereby driving an increase in Voc. The key challenge now lies in adapting industrial manufacturing equipment to realistically enable the large‑scale production of ultra-thin and flexible solar cells with low breakage rates.