Nonradiative Energy Transfer Enables a hv < E_g Response of Perovskite Quantum Dots in Si-Based Inorganic–Organic Hybrid Solar Cells

Abstract

High performance is a crucial factor in seeking a more competitive levelized cost of electricity for the extensive popularization of c-Si solar cells. Here, CsPbBr 3 quantum dots (QDs) have been first applied as the light-converting layer to enhance the full-spectrum light response, resulting in an ∼71% enhancement of power conversion efficiency within silicon-based solar cells. Remarkably, even if the photon energy is smaller than the bandgap of CsPbBr 3 QDs, the long-wavelength external quantum efficiency shows a significant increase. Such surprising results can be attributed to the nonradiative energy transfer (NRET) mechanism of CsPbBr 3 QDs, which can transfer longwavelength-generated dipoles into the Si base with the assistance of a Coulomb force. Furthermore, a dipole-transferring model, which considers that the Al 2 O 3 passivation layer would play a negative role in the NRET process, is creatively but supportively proposed. These results highlight a simple, low-cost but promising strategy to improve the performance of c-Si solar cells.N owadays, crystalline silicon (c-Si) based solar cells dominate ∼95% of the photovoltaic (PV) market. 1 So, even an insignificant performance improvement of these commercial c-Si solar cells, to seek a more competitive levelized cost of electricity (LCOE), is highly valuable. 2−4 Until now, a bunch of strategies have been demonstrated, such as constructing different stacked tandem even multijunction cell architecture (perovskite/c-Si tandem, 5−7 polymer/perovskite tandem, 8−10 or amorphous Si/c-Si tandem, 11−13 and so on), to overcome the Shockley-Queisser limit of ∼33% for single-junction c-Si solar cells. 14 For example, the perovskite thin film materials, attractive in recent years for their high spectral response, and low cost as well as a high initial performance of a single junction, 15−17 can be used as the top cell, to form perovskite/Si tandem solar cells. 18,19 However, there are lots of challenges in designing/fabricating tandem/ multijunction, such as photocurrent matching, tunnel junction, and so on. 20,21 Besides, the high-energy photons, particularly in the ultraviolet (UV) wavelength region, which have energy much higher than the bandgap, are mostly absorbed nearly at the surface of Si devices but provide few effective carriers for device performance because of more defect states at the interface. 22 Therefore, exploring an easier/simpler way to efficiently utilize these high-energy photons of short wavelength even the UV region for higher performance is needed, such as using light-converting layers in front of the c-Si solar cells may be a promising approach. 23−25