Transparent pn Junction\nin ZnCo<sub>2</sub>O<sub>4</sub>/Bi<sub>2</sub>WO<sub>6</sub> Quantum\nDots/WO<sub>3</sub> via Surface\nPlasma Modification for Photovoltaic Enhancement and Self-Cle

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