21.6%-Efficient Monolithic Perovskite/Cu(In,Ga)Se₂ Tandem Solar Cells with Thin Conformal Hole Transport Layers for Integration on Rough Bottom Cell Surfaces

Abstract

Perovskite-based tandem solar cells have proven to be suitable candidates to increase the power conversion efficiency (PCE) of conventional single-junction photovoltaic devices, such as those based on silicon and Cu(In,Ga)Se 2 (CIGSe) absorbers, beyond the Shockley-Queisser single-junction PCE limit. Here, we present a highly efficient monolithic perovskite/CIGSe tandem solar cell with a solution processed perovskite top cell fabricated directly on an asgrown, rough CIGSe bottom cell. To prevent potential shunting due to the rough CIGSe surface, a thin NiO x layer is conformally deposited via atomic layer deposition (ALD) on the ITO front contact of the CIGSe bottom cell. The performance is further improved by an additional layer of the p-type polymer PTAA at the NiO/perovskite interface. This novel hole transport bilayer enables a 21.6% stabilized PCE of the monolithic perovskite/CIGSe tandem device at 0.778 cm 2 active area. We use TEM/EDX measurements to investigate the deposition uniformity and conformality of the NiO x and PTAA layers. By comparing the performance of single-junction subcells with absolute photoluminescence measurements, we determine the contribution of the individual subcells to the tandem V OC , revealing that further fine-tuning of the recombination layers between the two subcells might improve the tandem V OC further. Finally, based on the obtained results we give guidelines on how to further improve monolithic perovskite/CIGSe tandems towards predicted PCE estimates above 30%.

Two‐Terminal Perovskites Tandem Solar Cells: Recent Advances and Perspectives

“…Monolithic perovskite/CIGSe tandem with NiOx/PTAA hole transport bilayer: f) schematic superimposed on the cross‐section image with all the layers depicted, g) J–V curves and EQE spectra. Adapted with permission . Copyright 2019, American Chemical Society.…”

“…An alternative fabricating process more favorable for the industrial application on large cell areas was recently presented by Jošt et al, who developed a monolithic tandem device with a Cs 0.05 (MA 0.17 FA 0.83 )Pb 1.1 (I 0.83 Br 0.17 ) 3 top‐cell fabricated directly on an as‐grown, nonpolished, rough CIGS bottom‐cell (Figure f–g). To prevent potential shunting caused by the relatively rough CIGS surface, a 10 nm thick ALD NiOx layer was conformally deposited on the front contact of the CIGS bottom‐cell.…”

Alkali Salts as Interface Modifiers in n‐i‐p Hybrid Perovskite Solar Cells

“…Organic–inorganic hybrid perovskite solar cells (PSCs) are of great promise for next generation solar energy conversion, in particular, because they exhibit ideal properties to enable low‐cost multijunction devices . After impressive power conversion efficiencies (PCEs) of over 23% have been reached on lab‐scale small‐area (<1 cm 2 ) devices, the scalability and stability of PSCs are now among the most important technological challenges.…”

Toward scalable perovskite‐based multijunction solar modules

“…Intrinsic electrical characteristics, optics of the layer stack, effectiveness of deposition techniques, all have significant impact on the overall performance of the multijunction devices . Recently, an all‐thin‐film monolithic perovskite‐CIGS multijunction solar cell with PCE of 21.6% on 0.8 cm 2 was demonstrated . Such advances demonstrate the attractive prospects of all‐thin‐film perovskite‐CIGS multijunction solar cells.…”