Transparent pn Junction in ZnCo₂O₄/Bi₂WO₆ Quantum Dots/WO₃ via Surface Plasma Modification for Photovoltaic Enhancement and Self-Cleaning

A self-cleaning transparent device in a Bi 2 WO 6 QD-modified ZnCo 2 O 4 /WO 3 pn junction is prepared via the sol–gel-hydrothermal-freeze-drying-surface plasma method. The ZnCo 2 O 4 /Bi 2 WO 6 QDs/WO 3 exhibits transmittance of ∼85%, photovoltaic enhancement of ∼1.6 × 10 3 -fold (PCE of ∼1.16%), stable output during 5 months, and good self-cleaning via surface hydrophobicity (contact angle of ∼131.5°). It is mainly attributed to the Bi 2 WO 6 QD and plasma modification; in addition to appropriate potential and high quantum yield, which can improve the carrier kinetic equilibrium for transparency–photovoltaic balancing, the surface plasma modification can also enhance the solar efficiency and carrier efficiency, while achieving the self-cleaning. Moreover, the extra hole carrier caused by the Co 3+ /Co 2+ mixed state and interstitial oxygen can optimize the kinetic equilibrium further, and the inorganic WO 3, Bi 2 WO 6 QDs, and ZnCo 2 O 4 with good physical–chemical stability can provide good structural stability for actual application effectively.