Transparent pn junction in CuCrO2/WO3 for enhanced photovoltaic response and stability <i>via</i> high entropy perovskite Ba(Ti0.2Zr0.2Sn0.2Hf0.2Ce0.2)O3 transition layer

A transparent pn junction comprising CuCrO2/Ba(Ti0.2Zr0.2Sn0.2Hf0.2Ce0.2)O3/WO3 was synthesized using a sol-gel-hydrothermal-annealing method. The CuCrO2/BaTiZrSnHfCe/WO3 achieves a transmittance of ∼83%–88%, with photovoltaic enhancement of ∼4.0 × 103-folds compared to the intrinsic device [photovoltaic conversion efficiency (PCE) of ∼1.22%], and it also demonstrates good stability over 5 months. This is mainly attributed to the BaTiZrSnHfCe HEO solid solution. In addition to an appropriate Fermi level/high QY, the BaTiZrSnHfCe HEO, with carrier inducing/injecting/driving by synergism of high entropy lattice distortion and charge compensation, can improve kinetic equilibrium for achieving PCE-transparency while increasing holes via Cu vacancies/interstitial oxygen. Moreover, inorganic CuCrO2, BaTiZrSnHfCe HEO, and WO3 maintain good structural stability, indicating promising applications for CuCrO2/BaTiZrSnHfCe/WO3 in optoelectronic devices.