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Mixed ion perovskite solar cells (PSC) are manufactured with a metal-free hole contact based on press-transferred single-walled carbon nanotube (SWCNT) film infiltrated with 2,2,7,-7-tetrakis(N,N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD). By means of maximum power point tracking, their stabilities are compared with those of standard PSCs employing spin-coated Spiro-OMeTAD and a thermally evaporated Au back contact, under full 1 sun illumination, at 60 °C, and in a N atmosphere. During the 140 h experiment, the solar cells with the Au electrode experience a dramatic, irreversible efficiency loss, rendering them effectively nonoperational, whereas the SWCNT-contacted devices show only a small linear efficiency loss with an extrapolated lifetime of 580 h.

Hybrid hole-transporting material and selective contact for perovskite solar cells was manufactured by industrially viable materials and methods.

Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAPbI3)0.85(MAPbBr3)0.15) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.

SUMMARYThis review presents an overview of the current state of research on nanostructured titanium dioxide dye solar cells (DSCs) on alternative substrates to glass. Replacing the traditionally used heavy, rigid, and expensive glass substrate with materials such as plastic foils or metal sheets is crucial to enable large volume cost-efficient roll-to-roll type industrial scale manufacturing of the cells and to make this solar cell technology properly competitive with silicon and thin film photovoltaic devices. One of the biggest problems with plastic substrates is their low-temperature tolerance, which makes sintering of the photoelectrode films impossible, whereas with metals, their corrosion resistance against the iodine-containing electrolyte typically used in DSCs limits the amount of metal materials suitable for substrates. However, significant progress has been made in developing new materials, electrode film deposition and post-treatment methods suitable for low-temperature processing. Also, metals that do not corrode in the presence of iodine electrolyte have been found and successfully employed as DSC substrates. The highest power conversion efficiencies obtained with plastic and metal substrates are already 7-9%, which is not far from the best glass cell efficiencies, 10-11%, and comparable also to, for example, amorphous silicon solar cell efficiencies. One of the most important of the remaining research challenges of DSCs on flexible substrates is to ensure that the long-term stability of the cells is realistic to consumer applications, for example, with providing efficient enough encapsulation to prevent water and other impurities penetration into the cells. Degradation mechanisms specific to metal-based cells are another issue that needs deeper understanding still. More exotic approaches such as depositing the DSC structure on optical fiber or employing carbon nanomaterials to increase the cell efficiency are also discussed in this paper.

Herein, we report use of [Li @C ]TFSI as a dopant for spiro-MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10-fold that of conventional devices using Li TFSI . Such high stability is attributed to the hydrophobic nature of [Li @C ]TFSI repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li @C ]TFSI could oxidize spiro-MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions.

A mixed-ion (FAPbI3)1−x(MAPbBr3)x perovskite solar cell was prepared under ambient conditions with an average efficiency of 17.6%.