penghuang

The recent advances in perovskite solar cells (PSCs) created a tsunami effect in the photovoltaic community. PSCs are newfangled high-performance photovoltaic devices with low cost that are solution processable for large-scale energy production. The power conversion efficiency (PCE) of such devices experienced an unprecedented increase from 3.8 % to a certified value exceeding 20 %, demonstrating exceptional properties of perovskites as solar cell materials. A key advancement in perovskite solar cells, compared with dye-sensitized solar cells, occurred with the replacement of liquid electrolytes with solid-state hole-transporting materials (HTMs) such as 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD), which contributed to enhanced PCE values and improved the cell stability. Following improvements in the perovskite crystallinity to produce a smooth, uniform morphology, the selective and efficient extraction of positive and negative charges in the device dictated the PCE of PSCs. In this Review, we focus mainly on the HTMs responsible for hole transport and extraction in PSCs, which is one of the essential components for efficient devices. Here, we describe the current state-of-the-art in molecular engineering of hole-transporting materials that are used in PSCs and highlight the requisites for market-viability of this technology. Finally, we include an outlook on molecular engineering of new functional HTMs for high efficiency PSCs.

It′s what′s inside that counts: The power conversion efficiency of the perovskite solar cells has significantly increased from 3.8 % to a certified value exceeding 20 %, highlighting the unique properties of perovskite materials. Here, we review the current progress in perovskite solar cells with particular focus on the hole-transport materials used in these high efficiency devices.

The application of conjugated materials in organic photovoltaics (OPVs) is usually demonstrated in lab-scale spin-coated devices that are processed under controlled inert conditions. Although this is a necessary step to prove high efficiency, testing of promising materials in air should be done in the early stages of research to validate their real potential for low-cost, solution-processed, and large-scale OPVs. Also relevant for approaching commercialization needs is the use of printing techniques that are compatible with upscaling. Here, solution processing of organic solar cells based on three new poly(2,7-carbazole) derivatives is efficiently transferred, without significant losses, to air conditions and to several deposition methods using a simple device architecture. High efficiencies in the range between 5.0 % and 6.3 % are obtained in (rigid) spin-coated, doctor-bladed, and (flexible) slot-die-coated devices, which surpass the reference devices based on poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT). In contrast, inkjet printing does not provide reliable results with the presented polymers, which is attributed to their high molecular weight. When the device area in the best-performing system is increased from 9 mm² to 0.7 cm², the efficiency drops from 6.2 % to 5.0 %. Photocurrent mapping reveals inhomogeneous current generation derived from changes in the thickness of the active layer.

Fabricate them in air: A series of poly(2,7-carbazole) derivatives are used to fabricate organic solar cells in air using roll-to-roll-compatible deposition methods. High efficiencies are obtained both in rigid and in flexible devices. Initial defects in photocurrent generation are identified when moving from millimeter-sized to centimeter-sized devices.

Flexible perovskite solar cells (FPSCs) have various applications such as wearable electronic textiles and portable devices. In this work, we demonstrate FPSCs on a titanium metal substrate employing solution-processed silver nanowires (Ag NWs) as the top electrode. The Ag NW electrodes were deposited on top of the spiro-MeOTAD hole transport layer by a carefully controlled spray-coating method at moderate temperatures. The power conversion efficiency (PCE) reached 7.45 % under AM 1.5 100 mW cm⁻² illumination. Moreover, the efficiency for titanium-based FPSCs decreased only slightly (by 2.6 % of the initial value) after the devices were bent 100 times. With this and other advances, fully solution-based indium-free flexible photovoltaics, advantageous in terms of price and processing, have the potential to be scaled into commercial production.

Bend it like Yongseok: Flexible perovskite solar cells (FPSCs) are prepared, with solution-processed silver nanowires (Ag NWs) as the top electrode on a titanium metal substrate. Deposition of the Ag NWs is carefully controlled using spray-coating at moderate temperatures. The devices reach high power conversion efficiencies (PCEs), retaining them even after bending 100 times.

Photocatalytic fuel cells (PFCs) are constructed from anodized photoanodes with the aim of effectively converting organic materials into solar electricity. The syntheses of the photoanodes (TiO₂, WO₃, and Nb₂O₅) were optimized using the statistical 2^k factorial design. A systematic study was carried out to catalog the influence of eleven types of organic substrate on the photocurrent responses of the photoanodes, showing dependence on the adsorption of the organic substrates and on the associated photocatalytic degradation mechanisms. Strong adsorbates, such as carboxylic acids, generated high photocurrent enhancements. Simple and short-chained molecules, such as formic acid and methanol, are the most efficient in the corresponding carboxylic acid and alcohol groups as a result of their fast degradation kinetics. The TiO₂-based PFC yielded the highest photocurrent and obtainable power, whereas the Nb₂O₅-based PFC achieved the highest open-circuit voltage, which is consistent with its most negative Fermi level.

Electric results! Photocatalytic fuel cells (PFCs) are constructed with the aim of effectively converting organic materials into solar electricity. The syntheses of the anodized photoanodes are optimized, the photoelectrochemical properties and the effect of various organic compounds are characterized, and the PFCs are constructed and assessed. PFC performance is affected by the adsorption and photocatalytic degradation of the organic compounds.