Perovskite/crystalline silicon tandem photovoltaic cells
As the light-absorbing layer of thin-film solar cells, organic-inorganic hybrid perovskite materials have the advantages of simple preparation process, high defect tolerance, and adjustable band gap. Typical systems include methylamine lead iodine (MAPbI3), formamidine lead iodine (FAPbI3 ), etc., are the most advanced photovoltaic materials. In just over ten years, the photoelectric conversion efficiency of perovskite single-junction photovoltaic cells has rapidly increased from 3.8% to 25.5%, which is close to the efficiency record of silicon-based solar cells. Perovskite semiconductor materials are compounds whose band gaps can be tuned from 1.2 eV to 3.2 eV by tuning the composition. The band gap of the perovskite material is adjusted to about 1.68 eV, and the tandem photovoltaic cell is composed of a crystalline silicon material with a band gap of 1.12 eV. The perovskite is used as the top cell to absorb short-wavelength high-energy photons, and the crystalline silicon is used as the bottom cell to absorb long low-energy photons of wavelengths. Sub-cells with different band gaps absorb light in different bands, which can reduce the thermal relaxation loss of photogenerated carriers and effectively improve the photoelectric conversion efficiency of photovoltaic cells.
The perovskite/crystalline silicon tandem photovoltaic cell can be understood as an upgrade of the traditional crystalline silicon photovoltaic cell technology, from a crystalline silicon single junction (single semiconductor material) cell to a tandem cell (two semiconductor materials in series) structure. The theoretical efficiency limit of perovskite/crystalline silicon double-junction tandem photovoltaic cells can be increased to 42.5%, and the actual laboratory efficiency record has reached 29.52%, which has exceeded the theoretical limit of single-crystalline silicon. Based on this, perovskite/crystalline silicon tandem photovoltaic cells can break through the original efficiency limit, thereby greatly reducing the overall power generation cost.
At present, the maximum photoelectric conversion efficiency of small-area single-junction perovskite photovoltaic cells developed by the thermal energy technology team exceeds nearly 25% (the world record is 25.5%), and the efficiency of small-area perovskite/crystalline silicon tandem photovoltaic cells exceeds 27%. The accelerated aging life is more than 2000 hours, which is at the international and domestic advanced level, and has the conditions for the prototype verification of industrial-scale large-area devices. In the next step, Thermal Energy plans to develop a complete process for preparing perovskite/crystalline silicon tandem photovoltaic cells on industrial-grade M6 (166 mm * 166 mm) silicon wafers, and achieve an efficiency target of 27% by the end of 2023.
