Recent progress on nanostructured carbon-based counter/back electrodes for high-performance dye-sensitized and perovskite solar cells

Biomass-Derived Materials in Perovskite Solar Cells: Recent Progress and Future Prospects

As a promising photovoltaic (PV) technology, perovskite solar cells (PSCs) have made significant progress in attaining high PCE, while challenges remain regarding stability and low cost. Conventional PSCs using noble metals (e. g., Au and Ag) as back electrodes and transparent conducting oxides as front electrodes contribute significantly to their high costs. PSCs comprising biomass-derived materials, such as biocarbon as back electrodes and flexible and transparent cellulosic substrates as front electrodes, offer a promising solution to address these issues. These approaches have the potential to simultaneously improve stability and decrease manufacturing costs, making PSCs closer to commercialization. This review article furnishes a comprehensive overview of recent developments in biocarbon-based perovskite solar cells (C-PSCs), focusing on various biomass-derived biocarbon materials utilized as back electrodes in different C-PSCs device structures. This article also compiles the advancement of flexible and transparent cellulosic substrate-based PSCs by highlighting the fundamentals of PSC and C-PSC architectures, the basics of biomass, and the synthesis of biocarbon. Finally, this review discusses the current challenges and future research directions for optimizing biocarbon materials and cellulosic substrates in PSC technology.

Screening novel candidates of ZL003-based organic dyes for dye-sensitized solar cells by modifying auxiliary electron acceptors: A theoretical study

In this work, a series of ZL003-based free-metal sensitizers with the donor-acceptor-π- conjugated spacer-acceptor (D-A-π-A) structure were designed by modifying auxiliary electron acceptors for the potential application in dye-sensitized solar cells. The energy levels of frontier molecular orbitals, absorption spectra, electronic transition, and photovoltaic parameters for all studied dyes were systematically evaluated using density functional theory (DFT)/time-dependent DFT calculations. Results illustrated that thienopyrazine (TPZ), selenadiazolopyridine (SDP), and thiadiazolopyridine (TDP) are excellent electron acceptors, and dye sensitizers functionalized by these acceptors have smaller HOMO-LUMO gaps, obviously red-shifted absorption bands and stronger light harvesting. The present study revealed that the photoelectric conversion efficiency (PCE) of ZL003 is around 13.42 % with a JSC of 20.21 mA·cm-2, VOC of 966 mV and FF of 0.688 under the AM 1.5G sun exposure, in good agreement with its experimental value (PCE = 13.6 ± 0.2 %, JSC = 20.73 ± 0.20 mA·cm-2, VOC = 956 ± 5 mV, and FF = 0.685 ± 0.005.). With the same procedure, the PCE values for M4, M6, and M7 were estimated to be as high as 19.93 %, 15.38 %, and 15.80 % respectively. Hence, these three dyes are expected to be highly efficient organic sensitizers applied in practical DSSCs.

Enhanced electrocatalytic properties in dye-sensitized solar cell via Pt/SBA-15 composite with optimized Pt constituent

The Low utilization and high cost of platinum counter electrode (CE) in the application of dye-sensitized solar cells has limited its large-scale manufacturing in the industry. Herein, a facile pyrolysis combination of Pt and SBA-15 molecular sieve (MS) formed 1.6-1.9 times higher amount and 2-3 times reduced dimension of Pt distributed within porous structure of SBA-15. The composite CE with 20 % of SBA-15 exhibited an enhanced power conversion efficiency of 9.31 %, exceeding that of absolute Pt CE (7.57 %). This superior performance owed to the promoted oxidation-reduction rate of I3-/I- pairs at the CE interface and the increased conductivity of CE materials attributed from well distributed Pt particles. This work has demonstrated the significance of utilizing porous molecular sieves for dispersing catalytic sites when designing a novel type of counter electrode and their application in DSSCs.

3D graphene: synthesis, properties, and solar cell applications

Three-dimensional (3D) graphene is one of the most important nanomaterials. This feature article highlights the advancements, with an emphasis on contributions from our group, in the synthesis of 3D graphene-based materials and their utilization in solar cells. Chemistries of graphene oxides, hydrocarbons, and alkali metals are discussed for the synthesis of 3D graphene materials. Their performances in dye-sensitized solar cells and perovskite solar cells (as counter electrodes, photoelectrodes, and electron extracting layers) were correlatively analyzed with their properties/structures (accessible surface area, electrical conductivity, defects, and functional groups). The challenges and prospects for their applications in photovoltaic solar cells are outlined.

Redox Shuttle-Based Electrolytes for Dye-Sensitized Solar Cells: Comprehensive Guidance, Recent Progress, and Future Perspective

A redox electrolyte is a crucial part of dye-sensitized solar cells (DSSCs), which plays a significant role in the photovoltage and photocurrent of the DSSCs through efficient dye regeneration and minimization of charge recombination. An I^-/I₃ ^- redox shuttle has been mostly utilized, but it limits the open-circuit voltage (V _oc) to 0.7-0.8 V. To improve the V _oc value, an alternative redox shuttle with more positive redox potential is required. Thus, by utilizing cobalt complexes with polypyridyl ligands, a significant power conversion efficiency (PCE) of above 14% with a high V _oc of up to 1 V under 1-sun illumination was achieved. Recently, the V _oc of a DSSC has exceeded 1 V with a PCE of around 15% by using Cu-complex-based redox shuttles. The PCE of over 34% in DSSCs under ambient light by using these Cu-complex-based redox shuttles also proves the potential for the commercialization of DSSCs in indoor applications. However, most of the developed highly efficient porphyrin and organic dyes cannot be used for the Cu-complex-based redox shuttles due to their higher positive redox potentials. Therefore, the replacement of suitable ligands in Cu complexes or an alternative redox shuttle with a redox potential of 0.45-0.65 V has been required to utilize the highly efficient porphyrin and organic dyes. As a consequence, for the first time, the proposed strategy for a PCE enhancement of over 16% in DSSCs with a suitable redox shuttle is made by finding a superior counter electrode to enhance the fill factor and a suitable near-infrared (NIR)-absorbing dye for cosensitization with the existing dyes to further broaden the light absorption and enhance the short-circuit current density (J _sc) value. This review comprehensively analyzes the redox shuttles and redox-shuttle-based liquid electrolytes for DSSCs and gives recent progress and perspectives.

Lignin Nanoparticles: Promising Sustainable Building Blocks of Photoluminescent and Haze Films for Improving Efficiency of Solar Cells

Films with the capacity for photoluminescence and haze, which can convert UV to visible light and enhance light management, are of great importance for optoelectronic devices. Here, taking advantage of the inherent fluorescence and self-assembly properties of lignin, we have developed a sustainable lignin-derived multifunctional dopant (L-MS-NPs) for fabricating optical films with haze, fluorescence, and room-temperature phosphorescence (RTP) together with poly(vinyl alcohol) (PVA). The optical films are used to improve the light-harvesting efficiency of solar cells. Specifically, attributed to the robust morphology in the film matrix, L-MS-NPs cause a rough morphology in the surface of an L-MS-NPs/PVA composite film, which eventually triggers the great optical haze. Additionally, L-MS-NPs inherit fluorescence properties from lignin and show fluorescence emission when embed in the film matrix. Moreover, the PVA film matrix can stabilize the excited triplet state, which finally induces RTP of L-MS-NPs. The combined haze, fluorescence, and RTP properties of the L-MS-NPs/PVA composite film enhances the power conversion efficiency (PCE) of dye-sensitized solar cells from ∼3.9 to ∼4.1%.