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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 (EQEff) within the visible range to select the front-cell and the absorption selectivity factor within the near-infrared spectrum (SNIR) 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. [ABSTRACT FROM AUTHOR]

A new method is developed to prepare RuO2 films through UVO treatment of solution-processed ruthenium(iii) acetylacetonate (Ru(acac)3) without thermal annealing. By introducing RuO2 as an anode buffer layer, highly efficient polymer solar cells (PSCs) have been achieved. The resultant RuO2 layer exhibits high light transmittance in the visible range. Remarkable improvements in the short-circuit current density (Jsc) of the PSCs can be achieved upon the introduction of the RuO2 buffer layer. The PSCs with the RuO2 anode buffer layer demonstrate improved photovoltaic performance in comparison with the devices using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as the anode buffer layer. The power conversion efficiency (PCE) of the PSCs based on P3HT:PCBM and P3HT:ICBA reaches as high as 4.19% and 7.07%, respectively. An even higher PCE of 7.45% is realized by adopting a new conjugated polymer, PBDTBDD, as the donor. The results demonstrate that RuO2 has great potential as a hole collection material for highly efficient PSCs. [ABSTRACT FROM AUTHOR]