Enhanced operational stability through interfacial modification by active encapsulation of perovskite solar cells

Abstract

Encapsulates are, in general, the passive components of any photovoltaic device that provides the required shielding from the externally stimulated degradation. Here we provide comprehensive physical insight depicting a rather non-trivial active nature, in contrast to the supposedly passive, atomic layer deposition (ALD) grown Al 2 O 3 encapsulate layer on the hybrid perovskite [(FA 0.83 MA 0.17 ) 0.95 Cs 0.05 PbI 2.5 Br 0.5 ] photovoltaic device having the configuration: glass/FTO/SnO 2 /perovskite/spiro-OMeTAD/Au/(6) Al 2 O 3 . By combining various electrical characterization techniques, our experimental observations indicate that the ALD chemistry produces considerable enhancement of the electronic conductivity of the spiro-OMeTAD hole transport medium (HTM), resulting in electronic modification of the perovskite/HTM interface. Subsequently, the modified interface provides better hole extraction and lesser ionic accumulation at the interface, resulting in a significant lowering of the burn-in decay and nearly unchanged charge transport parameters explicitly under the course of continuous operation. Unlike the unencapsulated device, the modified electronic structure in the Al 2 O 3 coated device is essentially the principal reason for better performance stability. Data presented in this communication suggest that the ionic accumulation at the spiro-OMeTAD/perovskite interface triggers the device degradation in the uncoated devices, which is eventually followed by material degradation, which can be avoided by active encapsulation.

Degradation Mechanisms in a Mixed Cations and Anions Perovskite Solar Cell: Mitigation Effect of the Gold Electrode

“…The oxygen and water barrier properties of the thin gold layer (100 nm) had not previously been identified and referenced in the literature. The beneficial effect of dense layers such as metal oxide layers deposited by atomic layer deposition has been described. − One could thus anticipate a generic protection against moisture and oxygen. However, the protective effect of this gold layer against the sole temperature stress in the absence of oxygen and water (C1 condition) had never been described.…”

Encapsulation and Stability Testing of Perovskite Solar Cells for Real Life Applications

“…Different from polymers, these films are typically deposited by various low pressure deposition methods, such as atomic layer deposition (ALD), sputtering, evaporation, etc. ALD deposited films, which could be encapsulation only ,, or incorporated as a part of the electrode, have also been reported. ALD deposited films can also be combined with other films to form a barrier multilayer for enhanced encapsulation properties. , For example, combining the ALD coated alumina film with a hydrophobic surface modification with 1 H ,1 H ,2 H ,2 H -perfluorodecyltrichlorosilane has also been shown to enhance the barrier performance against moisture ingress .…”

A Perspective on the Commercial Viability of Perovskite Solar Cells

“…Encapsulation, in contrast, isolates halide perovskite from the ambient atmosphere, creating a controlled inner environment (Figure 5d). [352,353] With current device materials, degradation rates depend on oxygen transmission rate (OTR) and water vapor transmission rate (WWTR) of the sealing system, [354] which must be in the order of 10 À4 À10 À6 cm 3 m À2 d atm and 10 À3 À10 À6 gm d À1 , respectively, to guarantee strong encapsulation performance. [355,356] It is thus important to improve not only the intrinsic stability of PSCs but also the effectiveness of the encapsulating system hand in hand.…”