Perovskite solar cells have emerged as a promising and highly efficient solar technology. Despite efficiencies continuing to climb, the prospect of industrial manufacture is hampered by concerns regarding the safety...
In this work, we study the influence of the distance between electrodes on the performance of dye-sensitized solar cells based on TiO using the organic dye LEG4 and a Cu(dmp) redox couple (dmp = dimethyl phenantroline). The solar cells are characterized by a large open circuit voltage of up to 1.03 V, and an efficiency of 8.2% has been achieved for a 5.3 μm thick TiO film using an epoxy resin-based sealed cell configuration with a minimal separation between electrodes. Transient short-circuit photocurrent measurements up to an intensity of 3 Suns show a significant decay in photocurrent after an initial peak current upon switching on the light for larger distance, resulting in a lower steady state photocurrent. For the smaller distance cells, the steady state photocurrent is linear with light intensity up to 2 Suns. Charge extraction measurements under short-circuit conditions show that reducing the distance between electrodes increases the electron collection efficiency and thus, the attainable photocurrent. Recombination losses increase with larger electrode separation distance and higher light intensity due to mass transport limitation of the redox mediator. Electrochemical impedance measurements confirm the effect of electrode distance on the redox couple transport, showing an additional loop with increasing distance. For the configuration where the TiO film is in very close proximity to the PEDOT-covered counter electrode, inductive behavior is observed at low frequencies. The inductive behavior disappears with the incorporation of an insulating porous ZrO layer. The equivalent circuit for the solar cell has been expanded to include this effect.
Perovskite photovoltaics have shown great promise in device efficiency but also the promise of scalability through solution‐processed manufacture. Efforts to scale perovskites have been taken through printable mesoporous scaffolds and slot die coating of flexible substrates roll‐to‐roll (R2R). However, to date there has been no demonstration of entirely R2R‐coated devices due to the lack of a compatible solution‐processable back electrode; instead, high‐value evaporated metal contacts are employed as a post process. Here, in this study, the combination of a low‐temperature device structure and R2R‐compatible solution formulations is employed to make a fully R2R printable device architecture overcoming interlayer incompatibilities and recombination losses. Therefore, the n–i–p device structure of SnO2/perovskite/poly(3,4‐ethylenedioxythiophene)/carbon is employed to form an ohmic contact between a p‐type semiconductor and printable carbon electrode. In particular, the results show that the small‐scale device efficiencies of 13–14% are achieved, matching the device performance of evaporated gold electrodes. Also, this entirely R2R‐coated perovskite prototype represents a game changer, reaching over 10% (10.8) stabilized power conversion efficiency with unencapsulated long‐term stability retaining 84% of its original efficiency over 1000 h under 70% RH and 25 °C.
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