Synergy of the transmittance fluctuation factor and absorption selectivity for efficient semitransparent perovskite/organic tandem solar cells with high color-fidelity

Semitransparent solar cells are promising power-generating windows for building integrated photovoltaics, and the color-fidelity is crucially important for their potential application. Herein, to obtain desirable neutral-colored perception while surmounting the single-junction efficiency barrier, a systematic method is introduced to design semitransparent tandem solar cells (ST-TSCs), and CsPbI2Br/PTB7-Th:IEICO-4F-based perovskite/organic tandem solar cells (P/O-TSCs) with outstanding color-fidelity are first reported. Above all, a numerical method, which includes the fluctuation factor of external quantum efficiency (EQE(ff)) within the visible range to select the front-cell and the absorption selectivity factor within the near-infrared spectrum (S-NIR) to assess the rear-cell, is established to construct the device structure. Second, the theoretical transmittance fluctuation factor within the visible range (TFFVIS) and absorption selectivity factor (S) are developed to evaluate ST-TSCs' color-fidelity and photovoltaic performance. Finally, a PTB7-Th layer is introduced to passivate the halogen vacancy defects of CsPbI2Br. As a result, the neutral-colored semitransparent P/O-TSCs with a color coordinate of (0.344, 0.349) are achieved, which possess an efficiency of 13.56%, an average visible transmittance of 26.28% and a color rendering index of 96.4. The synergistic effects of the transmittance fluctuation factor and light-absorption selectivity open the path to design and fabricate semitransparent P/O-TSCs with balanced efficiency and good color neutrality.