The exceptional magnetic, electrical, and optical properties exhibited by metal halide perovskites (MHPs) have garnered significant interest from the optoelectronic research community in recent decades. Perovskite solar cells (PeSCs) have gained substantial attention due to their inherent advantages, such as solution processability, tunable band gaps, high absorption coefficients, and long carrier diffusion lengths. To optimize the performance and stability of PeSCs, it is crucial to incorporate appropriate charge transport layers (CTLs) and/or interlayers. These CTLs need to possess suitable energy levels for efficient charge injection and transport, while effectively blocking opposite charges. Additionally, the CTL located beneath the perovskite layer plays a critical role as it significantly influences the crystal growth of the perovskite layer and affects the presence of interfacial defects. In this presentation, a new series of conjugated polyelectrolytes (CPEs) will be introduced as ideal interfacial layers and CTLs for various PeSCs devices.
KEYWORDS: Solar cells, Photovoltaics, Solar energy, Silicon, Perovskite, Manufacturing, Sustainability, Dye sensitized solar cells, Design, Energy efficiency
This report provides a snapshot of emerging photovoltaic (PV) technologies. It consists of concise contributions from experts in a wide range of fields including silicon, thin film, III-V, perovskite, organic, and dye-sensitized PVs. Strategies for exceeding the detailed balance limit and for light managing are presented, followed by a section detailing key applications and commercialization pathways. A section on sustainability then discusses the need for minimization of the environmental footprint in PV manufacturing and recycling. The report concludes with a perspective based on broad survey questions presented to the contributing authors regarding the needs and future evolution of PV.
Over the past few decades, organic solar cells (OSCs) have made a significant progress, showing their great potential for low-cost, flexible, lightweight, portable and large-area energy-harvesting devices. In recent years, nonfullerene acceptors have emerged as a new candidate of n-type materials to overcome the disadvantages of fullerene derivatives in tuning optical and electronic properties. The strong and easily adjustable absorption characteristics of nonfullerene acceptors have been considered as a strong point compared to fullerene-type structures, showing a photovoltaic efficiency over ~19%. To further optimize the OSCs for next generation green energy sources, several important points need to be considered carefully. Here we discuss the fundamental correlations between molecular structure, exciton diffusion length, film morphology and device performance in new nonfullerene acceptor-based OSCs. In addition, perovskite solar cells (PeSCs) have also attracted extensive attention because of their inherent advantages such as solution processability, band-gap tunability, high absorption coefficient, and long carrier diffusion length. It has been successfully demonstrated that their power conversion efficiencies exceed 25%, which becomes similar with the highest PCE for crystalline Si solar cells. For PeSCs applications, appropriate charge transport layers (CTLs) are crucial for device performance and stability. The CTLs should have suitable energy levels for effective charge injection/transport while blocking opposite charges. Moreover, the CTL below the perovskite layer is critical because it significantly affects the crystal growth of the perovskite layer and its interfacial defects. In this presentation, a new series of conjugated polyelectrolytes is reported as an ideal interfacial layer and CTLs in PeSCs.
There is mounting evidence that long-range charge separation determines the efficiency of organic photovoltaic cells, yet different mechanisms remain under debate. One class of proposed mechanism is ultrafast coherent long-range charge separation, and another is a slower process whereby charges incoherently hop apart with a transiently enhanced mobility due to morphology and disorder. Here, we use transient absorption spectroscopy to probe incoherent charge separation dynamics in two different ways. First, we use a family of polymers whose backbone structures allows us to compare 2- phase donor-acceptor morphologies with 3-phase morphologies that feature an intermixed region. In the 3-phase system, we see pronounced spectral signatures associated with charges (holes) occupying the disordered intermixed region, and we track separation via biased charge diffusion to more ordered neat regions on the timescale of hundreds of picoseconds. Secondly, by resolving bimolecular charge recombination at high excitation density, we show that charge mobilities must be substantially enhanced on early timescales, which may be sufficient for separation to occur. Together, these measurements provide support for models of incoherent and relatively slow charge separation.
KEYWORDS: Fluorescence resonance energy transfer, Luminescence, Polymers, Energy efficiency, Molecules, Absorption, Resonance energy transfer, Picosecond phenomena, Energy transfer, Time resolved spectroscopy
We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.
Solvent effects were studied in fluorescence resonance energy transfer (FRET) from a cationic polyfluorene copolymer
(FHQ, FPQ) to a fluorescein (Fl)-labeled oligonucleotide (ssDNA-Fl). Upon addition of dimethyl sulfoxide (DMSO),
optical properties of the polymers and the probe dye were substantially modified. And the FRET-induced Fl emission
was measured by directly exciting the polymer within the complex, polymer/ssDNA-Fl. The FRET signal was
successfully modulated with changing the DMSO content. In the case of FHQ, the FRET-induced Fl emission was
seriously quenched in phosphate buffer solution (PBS), while a salient FRET signal was observed in a 80 vol%
DMSO/PBS mixture (36.8 time higher than that in PBS). The FPQ-sensitized FRET signal was also 3.8-fold amplified
by the presence of DMSO. That result is from the decrease of hydrophobic interactions between the polymer and
ssDNA-Fl, which induces the weaker polymer/ssDNA-Fl complexation with longer intermolecular separation. The
gradual decrease in Fl PL quenching with increasing the DMSO content was investigated by measuring the Stern-
Volmer quenching constants (3.3-4.2 × 106 M-1 in PBS, 0.56-1.1 x 106 M-1 in 80 vol% DMSO) in PBS/DMSO mixtures.
The substantially reduced PL quenching would amplify the resulting FRET Fl signal. This approach suggests a simple
way of modifying the fine-structure of polymer/ssDNA-Fl and improving the detection sensitivity in conjugated
polymer-based FRET bioassays.
A new fully functionalized photorefractive polyimine was prepared by the condensation polymerization between a photoconducting carbazole derivative, 9-(2- ethylhexyl)carbazole-3,6-dicarbaldehyde, and a nonlinear optical stilbene chromophore, 4-[N,N-bis(2- aminoethyl)amino]-4'-nitrostilbene. It showed excellent solubility in common organic solvents such as chloroform, cyclohexanone, tetrahydrofuran, etc. and high optical quality films were obtained by free standing film casting. Very high second order optical nonlinearity with d33 equals 120 pm/V was observed by second harmonic generation at the fundamental 1064 nm wavelength. In demonstrated good thermal stability of the aligned dipoles by electric field up to ca. 125 degrees C. The diffraction grating was formed by the interference of two coherent Ar-ion laser beam at the wavelength of 488 nm. A holographic diffraction efficiency of about 15 percent has been achieve din a 10 micrometers -thick film. Storage state of our film shows remarkably long stability at room temperature.
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