8:30 AM - EN02.06.03
Late News: Rational Design of Photoelectrochemical Perovskite-BiVO4 Tandem Devices for Selective Syngas Production
Virgil Andrei1,Geani Ucoski1,Motiar Rahaman1,Chanon Pornrungroj1,Esther Edwardes Moore1,Bertrand Reuillard1,Qian Wang1,Demetra Achilleos1,Robert Jagt1,Chawit Uswachoke1,Hannah Joyce1,Robert Hoye1,Judith MacManus-Driscoll1,Richard Friend1,Erwin Reisner1
University of Cambridge1
Metal halide perovskites have recently emerged as promising alternatives to commonly employed light absorbers for solar fuel synthesis.[1,2] These semiconductors enabled photoelectrochemical (PEC) perovskite-BiVO4 tandem devices which can perform unassisted water splitting,[3,4,6] as well as the more challenging CO2 reduction to syngas.[5,7] While the bare perovskite light absorber is rapidly degraded by moisture, recent developments in the device structure have led to substantial advances in the device stability, from seconds to days.
In this contribution, we give an overview of the latest progress from the field of perovskite PEC devices, introducing design principles to improve their performance and reliability. For this purpose, we will discuss the role of charge selective layers in increasing the device photocurrent and photovoltage, by fine-tuning the band alignment and enabling efficient charge separation. A further beneficial effect of hydrophobicity is revealed by comparing devices with different hole transport layers (HTLs). A threefold increase in the lifetime of perovskite photocathodes is obtained by replacing a hydrophilic PEDOT:PSS HTL with an inorganic NiOx HTL. A further leap in stability up to 96 h can be demonstrated by introducing a hydrophobic PTAA HTL, which acts as an additional barrier to lateral moisture infiltration while further increasing the onset potential for H2 evolution to approximately 1.0 V vs. RHE.
On the manufacturing side, we will provide new insights into how appropriate encapsulation techniques can extend the device lifetime to a few days under operation in aqueous media.[3,5] Many prototypes rely on low melting alloys as encapsulants, however the demand on rare elements can be detrimental for the overall cost and scalability of the tandems, whereas metals can suffer from chemical corrosion. To avoid these drawbacks, we introduce graphite epoxy paste as a conductive, hydrophobic encapsulant.[6,8] This abundant, metal-free composite can reduce the device cost while enabling a more facile integration of perovskite devices with inorganic,[6,7] molecular and bio-catalysts. The combined advantages of these approaches are demonstrated in a perovskite-BiVO4 tandem configuration, leading to selective unassisted CO2 reduction to syngas.
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