“…Especially, special attention has been paid to strontium molybdate (SrMoO 4 ) owing to its outstanding thermal and chemical stability, water stability and resistance against irradiation damage. [28][29][30][31] Herein, we have synthesized Er 3+ and Yb 3+ co-doped strontium molybdate (SrMoO 4 ) NPs for the first time and demonstrated their versatile application in organic/inorganic HSCs, in which TiO 2 is used as the electron acceptor because of its photosensitivity, nontoxicity, low-cost and environmental stability, etc., [32][33][34] and the well-known conducting polymer poly(thieno [3,4-b]-thiophene/ benzodithiophene) (PTB7) 35 is used as the electron donor. These HSCs are different from polymer solar cells (PSCs), which, as organic photovoltaics (OPVs), have been extensively studied due to their promising advantages including low-cost manufacture, robust and flexible mechanical properties, low-cost raw materials, and light weight, etc.…”