A large-area luminescent downshifting layer containing an Eu3+ complex for crystalline silicon solar cells†
The spectral mismatch between the distribution of sunlight (AM1.5G) and crystalline silicon (c-Si) solar cells is one of the most important limiting factors of the conversion efficiency of photovoltaic (PV) devices. As an effective solution, the use of the luminescence down-shifting (LDS) technique is an important way to improve the short-wavelength response of a solar cell by shifting high-energy photons to the visible range. Herein, a large-area (17 × 17 cm2) luminescent thin film consisting of a ternary europium (Eu3+) complex and polyvinyl alcohol (PVA) was successfully constructed through a solution casting method and further developed as an effective LDS layer to improve the photoelectric conversion efficiency of c-Si solar cells with a large active area (235 cm2). The self-standing LDS layer is flexible, transparent and easily attachable to the surface of the solar cell module. Compared with the uncoated c-Si solar cell, the one coated with the LDS layer displayed an enhancement of ∼15% in external quantum efficiency (EQE) due to the high luminescence quantum yield of the Eu3+ complex doped inside the layer. These results demonstrate that use of a large area luminescent film embedding an Eu3+ complex is a versatile and effective strategy to improve the conversion efficiency of large size PV devices, giving rise to its great potential application as an LDS material.