Abstract Flexible semitransparent perovskite solar cells (PVSCs) hold promising applications on buildings and unmanned vehicles with irregular surfaces. Efficient wide-bandgap PVSCs are a determining factor for building perovskite-based tandem cells, in which energy level alignment plays significant roles in reducing nonradiative recombination loss at interfaces. Here, we report on the fabrication of efficient flexible semitransparent wide-bandgap PVSCs with gradient energy level alignments at both electron- and hole-selective contacts. We design a triple-electron-selective contact as electron transport layers with gradient Fermi level alignment with the conduction band of wide-bandgap perovskite, which consists of trans-1,2-Diaminocyclohexane-N,N,N′,N′-tetraacetic (CyDTA), tin dioxide (SnO2), and CyDTA-complexed SnO2. Moreover, an ultrathin gold layer embedded between 2,2′,7,7′-tetrakis(N,N-bis(p-methoxy-phenyl)amino)-9,9′-spirobifluorene (spiro-OMeTAD) hole transport layer and molybdenum oxide protection layer facilitates effective hole transport to the anode. We conduct comprehensive and solid simulation at both charge-selective contacts to reveal the working mechanisms. The champion flexible semitransparent 1.75 eV wide-bandgap PVSC achieves an efficiency of 15.02% with excellent light transparency of around 70% beyond the wavelength of 700 nm, enabling all-flexible perovskite/Cu(In,Ga)Se2 tandem devices with efficiencies beyond 21%.