Close-Spaced Sublimation Processed Environment-Friendly Planar Heterojunction Antimony Sulfide Solar Cells
Ru Zhou, Biao Guo, Wentao Wu, Huan Wang, Haihong Niu, Lei Wan
Abstract
The exponential growth of the Internet of Things (IoTs) electronics calls for the development of more energy-saving solutions to replace commonly used batteries. The indoor photovoltaics (IPVs), capable of harvesting energy from ambient lighting, emerge as an advanced energy-supply technology for sustainable IoTs. The binary semiconductor antimony sulfide (Sb2S3) has a suitable bandgap of ~1.75 eV, close to the optimal value for IPVs. In this work, environment-friendly planar heterojunction Sb2S3 solar cells using TiO2 buffer layers were constructed via close-spaced sublimation (CSS). Through careful characterization of morphological, structural, and optoelectronic properties, it is revealed that, compared to the conventional CdS-based Sb2S3 films, the TiO2-based Sb2S3 films exhibit more compact morphology, improved [hkl, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${l} \ne ~0$ </tex-math></inline-formula>]-orientation, and more favorable band structure. Particularly, the significantly reduced parasitic absorption of TiO2 buffer layers over the short-wavelength range contributes to the remarkable photocurrent enhancement of devices. As a result, the TiO2/Sb2S3 heterojunction device yields a power conversion efficiency (PCE) of 4.55% under one-sun (AM1.5G, 100 mW cm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{2}}$ </tex-math></inline-formula>), outperforming that of the CdS/Sb2S3 device (4.11%). To the best of our knowledge, this is the highest efficiency value reported thus far for CSS-processed Sb2S3 systems. Moreover, an appreciable indoor efficiency of 12.14% is achieved for the TiO2/Sb2S3 solar cell under 1000-lx white light-emitting diode (WLED) illumination. This work manifests the great potential of CSS-processed environment-friendly planar heterojunction Sb2S3 solar cells for highly efficient and stable IPVs.