Kunal Datta¹,Yifeng Zhao²,Bruno Branco¹,Junke Wang¹,Valerio Zardetto³,Nga Phung¹,Dong Zhang^3,1,Andrea Bracesco¹,Willemijn Remmerswaal¹,Luana Mazzarella²,Martijn Wienk¹,Mariadriana Creatore¹,Olindo Isabella²,René Janssen¹

Technische Universiteit Eindhoven¹,Delft University of Technology²,TNO-Solliance³

Abstract

Technische Universiteit Eindhoven¹,Delft University of Technology²,TNO-Solliance³

The intermittency of solar radiation is a key characteristic that impedes the widespread use of photovoltaic systems. As a result, a critical component of any decarbonized energy economy is solar electricity storage for release on demand.[1] Hydrogen (H2) evolution through electrochemical (EC) water splitting is an effective method for energy storage due to the high energy density of H2 fuel. However, present-day H2 generation relies on byproducts of fossil fuel extraction leading to a high indirect carbon cost.[2] Photovoltaic (PV)-assisted EC water splitting methods that employ concentrated photovoltaics, on the other hand, use inorganic multijunction devices whose high manufacturing costs can undermine future commercial competitiveness. As a result, a cost-effective PV device delivering high current without light concentration, coupled to a flow EC system, can potentially provide an efficient method for H2 generation.[3] Metal halide perovskite semiconductors have been used to develop high-performance photovoltaic devices. Their tunable optical bandgap, high defect tolerance, and easy processing, are assets that allow their use in efficient multijunction devices.[4] As a result, high open-circuit voltages can be achieved which results in a high current at the operating potential for water splitting (> 1.23 V). This work describes the development of 1 cm2 active area all-perovskite and perovskite-silicon tandem solar cells by combining wide-bandgap perovskites with lead-tin based narrow-bandgap perovskite and silicon heterojunction bottom-cells respectively. Upon integrating with continuous flow EC cells, high solar-to-hydrogen (STH) conversion efficiencies can be achieved without using light-concentration techniques. Mixed-halide wide-bandgap perovskite compositions are developed for each multijunction structure and the defect-rich interface between the perovskite and the electron transport layer is passivated in order to increase radiative yield. Recombination layers in the multijunctions, based on thin atomic layer deposited (ALD) NiOx (perovskite-silicon) and SnOx (all-perovskite) layers, are used to maintain charge neutrality while ensuring low interfacial losses. The ALD NiOx interfacial layer increases surface hydroxyl content, thereby improving the binding of self-assembled hole-transporting monolayer (2PACz) in the top-cell in the perovskite-silicon tandem device.[5] In the all-perovskite tandem solar cell, the SnOx layer also acts as a solvent barrier to protect underlying layers from damage from subsequent solution processing steps.[6] Lastly, advanced optical simulations are used to identify key regions of parasitic absorption and reflection losses, which are mitigated by light-management strategies to yield current-matched tandem devices with a power conversion efficiency of > 23% (all-perovskite) and > 25% (perovskite-silicon) in 1 cm2 active area solar cells. By integrating the device with a flow electrochemical cell using RuO2 and Pt catalysts for H2 and O2 evolution respectively, a continuous water splitting system with a high STH conversion efficiency of > 18% (with all-perovskite) and > 21% (with perovskite-silicon) is achieved. [1] International Energy Agency, World Energy Outlook 2020, Paris, 2020. [2] F. Lehner, D. Hart, in Electrochem. Power Sources Fundam. Syst. Appl., Elsevier, 2022, pp. 1–36. [3] C. A. Rodriguez, M. A. Modestino, D. Psaltis, C. Moser, Energy Environ. Sci. 2014, 7, 3828. [4] M. T. Hörantner, T. Leijtens, M. E. Ziffer, G. E. Eperon, M. G. Christoforo, M. D. McGehee, H. J. Snaith, ACS Energy Lett. 2017, 2, 2506. [5] N. Phung, M. Verheijen, A. Todinova, K. Datta, M. Verhage, A. Al-Ashouri, H. Köbler, X. Li, A. Abate, S. Albrecht, M. Creatore, ACS Appl. Mater. Interfaces 2022, 14, 2166. [6] J. Wang, V. Zardetto, K. Datta, D. Zhang, M. M. Wienk, R. A. J. Janssen, Nat. Commun. 2020, 11, 5254.