Abstract Organic light‐emitting diodes (OLEDs) have emerged as a key technology in display and lighting applications owing to their high contrast, broad color gamut, and mechanical flexibility. However, their limited light extraction efficiency and inadequate charge transport capability present major barriers to improved performance. This study innovatively introduces diatomite, a naturally derived silica material, as a sustainable and cost‐effective means to enhance OLED performance. Diatomite is purified and etched with NaOH to tailor its structural and optical properties. When incorporated into OLED substrates, such diatomite layers considerably enhance light scattering. Devices with 10 wt.% diatomite achieve the highest current efficiency, striking a balance between scattering enhancement and film quality. In contrast, 20 wt.% diatomite results in reduced efficiency owing to increased surface roughness. Optical simulations confirm increased scattering efficiency and indicate that diatomite serves as an effective scattering medium. A large‐area (1500 mm 2 ) OLED cell is also fabricated on a diatomite‐modified substrate. Overall, these findings highlight the transformative potential of diatomite in advancing OLED technology, offering a sustainable pathway toward high‐performance, large‐area, and flexible devices.