The development of emerging photovoltaic technology has promoted the innovation of building-integrated photovoltaics (BIPV), not only in lower cost and simpler processing technology but also in a variety of additional features, such as flexibility and transparency. Semi-transparent solar cells that allow partial transmission of visible light are excellent candidates for BIPVs owing to their unique properties and potential for integrated energy solutions. In this work, we present a straightforward and highly reproducible protocol for depositing extremely uniform and ultra-thin perovskite layers. Our solution-processed perovskite solar cells, fabricated on flexible polymer 2 substrates with large active area (1 cm2), achieved a noteworthy 5.7% power conversion efficiency (PCE) under standard conditions (AM 1.5G radiation, 100 mW cm-2) accompanied by an Average Visible Transmittance (AVT) of 21.5% for full device architecture with 10 nm thick silver electrode. We present a simple yet elegant fabrication procedure for semi-transparent perovskite solar cells without any additional antireflective layers. Furthermore, we fabricated working perovskite solar cells with the thinnest active layer of spin-coated MAPbI3 reported so far (10 nm) exhibiting 1.9% PCE and 41.1% AVT (62.9% AVT without electrode). These results hold great promise for the integration of perovskite-based semi-transparent solar cells into real-world applications, advancing the landscape of renewable energy.