4‑T tandem solar cells was constituted of a semi‑transparent organic solar cells and the Cu₂ZnSn（S，Se）₄ solar cells. The anti‑reflection of the pyramidal micron polydimethylsiloxane （PS‑PDMS） was applied to trap the sunlight. The impact of size and position of PS‑PDMS on the performance of 4‑T tandem solar cells were analyzed. The width size of the micro‑pyramidal structure was various of 9~18 μm， and the results showed that 9 μm width of PS‑PDMS films could achieve the most significant anti‑reflection effect when it was pasted on the bottom cell of 4‑T tandem solar cells. 11.26% PCE of the 4‑T tandem solar cells was obtained. Compared with that of the single Cu₂ZnSn（S，Se）₄ solar cells， the optimal PCE of 4‑T tandem solar cells increased by 27.51%.