Neutral-Colored Transparent Crystalline Silicon Photovoltaics

Crystalline silicon (c-Si) is not used for developing transparent photovoltaics, owing to its opaque nature. Furthermore, adding optical transparency to a conventional c-Si wafer is one of the most challenging problems in this field. Here, we demonstrate the development of a neutral-colored transparent c-Si substrate using a 200-μm-thick c-Si wafer, which is known to be intrinsically opaque. Transparent c-Si substrates were fabricated by placing microhole-shaped light transmission windows on a bare c-Si wafer. These windows were designed to enable the transmission of all incident visible light through the substrate, resulting in a colorless substrate. A light absorption area was also designed on the wafer to efficiently absorb incident light. As a representative application, solar cells fabricated using the neutral-colored transparent c-Si substrate showed a power conversion efficiency of up to 12.2%. Therefore, our transparent c-Si solar cells present a unique opportunity to develop next-generation colorless transparent photovoltaics. Transparent solar cells are attractive energy conversion devices because they can be used in various applications in our daily life, such as building-integrated photovoltaics. However, transparent solar cells developed to date have limitations in efficiency and stability. Crystalline silicon (c-Si) is one of the best candidates to develop transparent solar cells with high efficiency and stability, because conventional c-Si solar cells are known to exhibit high efficiency and long-term stability compared with other solar cells. However, the opaque characteristic of the c-Si wafer hinders the development of transparent solar cells using c-Si. Here, we present a novel approach to develop neutral-colored transparent c-Si solar cells that exhibit the highest efficiency among neutral-colored transparent solar cells developed to date. Furthermore, we believe that this study makes a significant contribution not only to the field of photovoltaics but also to various transparent electronics. We report a neutral-colored transparent c-Si substrate using a 200-μm-thick c-Si wafer, which is known to be opaque. The transparent c-Si substrate shows a completely neutral color, similar to glass without a transmission cut-on wavelength. In addition, the transmittance of the transparent c-Si substrate is systematically tuned under the full solar spectrum. As a representative application, the transparent solar cells fabricated with the substrate developed in this study show a power conversion efficiency of up to 12.2%.