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Passive thermoelectric devices that utilize radiative cooling and solar heating have witnessed significant advancements in power generation. However, their applications and promotions are limited due to the low and unsustainable output. In this study, we propose a compact passive thermoelectric device (TED) consisting of a thermoelectric generator (TEG) equipped with a radiative cooler (RCer) and a solar absorber (SAer) for 24-h electricity generation. The RCer is made of a high-scattering porous cellulose film with a thickness of 100 μm. It is coated onto the TEG's sky-facing terminal which serves as the cold end. The SAer is made of an aluminum substrate coated with black paint. It is attached to the opposite TEG terminal which serves as the hot end. By compactly integrating the RCer and SAer, the proposed TED can harvest energy from the space for continuous electric power generation with manageable implementations. Outdoor experiments have shown that during a clear daytime, the maximum temperature difference between the TEG ends reached 7.7°C, with an average of 2.8°C. During the nighttime, the maximum temperature difference between TEG ends could reach 1.7°C, with an average of 0.9°C. The maximum power outputs during daytime and nighttime are 351.6 mW·m−2 and 31.0 mW·m−2, respectively. This study introduces a conceptual design for a compact passive TED and lays the foundation for practical applications in powering outdoor microdevices.