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Portable electronic devices have become increasingly widespread. Because these devices cannot always be tethered to a central grid, powering them will require low-cost energy harvesting technologies. As a response to this anticipated demand, this study demonstrates transparent organic solar cells fabricated on flexible substrates, including plastic and paper, using graphene as both the anode and cathode. Optical transmittance of up to 69% at 550 nm is achieved by combining the highly transparent graphene electrodes with organic polymers that primarily absorb in the near-IR and near-UV regimes. To address the challenge of transferring graphene onto organic layers as the top electrode, this study develops a room temperature dry-transfer technique using ethylene-vinyl-acetate as an adhesion-promoting interlayer. The power conversion efficiency achieved for flexible devices with graphene anode and cathode devices is 2.8%–3.8% at for optical transmittance of 54%–61% across the visible regime. These results demonstrate the versatility of graphene in optoelectronic applications and it is important step toward developing a practical power source for distributed wireless electrical systems.

A visibly transparent, flexible solar cell with all-graphene electrodes is fabricated by combining the high optical transmittance of graphene with organic polymers that absorb primarily in the near-IR and near-IV regimes. The fabrication process is enabled by developing a universal room temperature dry graphene transfer method. The devices exhibit exceptional optical transmittance and mechanical flexibility.

An active and stable photocatalyst to directly split water is desirable for solar-energy conversion. However, it is difficult to accomplish overall water splitting without sacrificial electron donors. Herein, we demonstrate a strategy via constructing a single site to simultaneously promote charge separation and catalytic activity for robust overall water splitting. A single Co₁-P₄ site confined on g-C₃N₄ nanosheets was prepared by a facile phosphidation method, and identified by electron microscopy and X-ray absorption spectroscopy. This coordinatively unsaturated Co site can effectively suppress charge recombination and prolong carrier lifetime by about 20 times relative to pristine g-C₃N₄, and boost water molecular adsorption and activation for oxygen evolution. This single-site photocatalyst exhibits steady and high water splitting activity with H₂ evolution rate up to 410.3 μmol h⁻¹ g⁻¹, and quantum efficiency as high as 2.2 % at 500 nm.

A good CoP: Highly active and stable Co₁-P₄ single-sites confined on polymeric g-C₃N₄ are prepared. The resulting single-site photocatalyst performs spontaneous overall water splitting with high H₂ evolution rates under solar irradiation without the need for a sacrificial donor.

Indene C₆₀ and C₇₀ bisadducts (IC₆₀BA and IC₇₀BA) have relatively high lowest unoccupied molecular orbital energies. In poly(3-hexylthiophene) (P3HT)-based polymer solar cells (PSCs), this produces an increase in open-circuit voltage (V_OC) and power conversion efficiency (PCE). However, ICBA synthesis produces a mixture of regio-isomers with different indene spatial orientations (2, 5, and 12 o'clock) that alter the IC₇₀BA molecular packing when mixed with P3HT. In this paper, how the IC₇₀BA regio-isomerism affects the PSC performance is examined by investigating the molecular packing of P3HT:IC₇₀BA layers with different regio-isomeric ratios. For the first time, non-destructive spectroscopic ellipsometry is used to investigate the effect of the fabrication conditions on the P3HT/IC₇₀BA vertical volume fraction distribution and the results are attributed to the spatial arrangement of the regio-isomers. It is demonstrated that this unambiguously affects the PSC performance. As a result, record device efficiencies are repeatedly attained for standard architecture P3HT:IC₇₀BA PSCs with photoactive areas of 0.43 cm², achieving 5.9 (±0.4)% PCE (n = 15). With control of the IC₇₀BA constituent, device PCEs vary from below 2.2% to peak values above 6.7%, among the highest recorded PCEs for a P3HT combination, highlighting the importance of the molecular phase separation for high-efficiency devices.

A crucial factor to determine the power conversion efficiency of poly(3-hexylthiophene) (P3HT):indene C₇₀ bisadducts (IC₇₀BA)-based polymer solar cells is the variation of the regio-isomeric ratio of IC₇₀BA, which affects the molecular packing of the bulk-heterojunction blend between IC₇₀BA and P3HT. This is directly related to the device power conversion efficiency, which can vary from below 2.2% to above 6.7%.

C.-Z. Li, H. Chen and co-workers present, on page 9729, for the first time, efficient non-fullerene tandem organic solar cells (OSCs) by utilizing all non-fullerene acceptor-based bulk heterojunctions as sub-cells. A high power conversion efficiency of 8.48% is achieved with an ultra-high open-circuit voltage of 1.97 V, which is the highest voltage value reported to date feasible for water splitting among the efficient tandem OSCs.

A novel 3D Co–N_x|P-complex-doped carbon grown on flexible exfoliated graphene foil is designed and constructed for both electrochemical and photoelectrochemical water splitting. The coordination of Co–N_x active centers hybridized with that of neighboring P atoms enhances the electron transfer and optimizes the charge distribution of the carbon surface, which synergistically promotes reaction kinetics by providing more exposed active sites.

Morphology plays a vital role on the performance of organic photovoltaics. However, our understanding of the morphology-performance relationships for organic photovoltaics remains lacking. Specifically, it is still an open question why some bulk-heterojunction blends exhibit electric field dependent J–V curves, while others do not. Through detailed fs-μs transient absorption spectroscopy and morphology studies on the representative bulk-heterojunction type small molecule (SM) donor system, a picture of different J–V behaviors from morphology aspects and excited dynamics is revealed. Our findings reveal that amorphous morphology in the lack of percolated pathways leads to the formation of strongly bound charge transfer states (CTSs), which accounts for about one third of the photoexcited species. Therefore, field-dependent J–V curves are obtained as these CTSs mainly undergo geminate recombination or function as interfacial traps for nongeminate recombination. On the other hand, the CTSs are totally suppressed after post-treatment owning to the formation of bicontinuous morphology, which results in very high efficiencies from exciton generation, diffusion, dissociation to charge extraction, thus contributes to field-independent J–V characteristics. The insights gained in this work provide the effective guidelines to further optimize the performance of bulk-heterojunction type SM-organic photovoltaics through judicious morphology control and engineering.

A picture of different J–V behaviors from morphology aspects and excited dynamics is revealed through fs-μs transient absorption measurements. The amorphous donor morphology without percolated pathways facilitates the formation of strongly bound charge transfer states, which results in the field-dependent J–V curves as these charge transfer states can only be dissociated and extracted by applying very large reverse voltages.

The incorporation of multiple donors into the bulk-heterojunction layer of organic polymer solar cells (PSCs) has been demonstrated as a practical and elegant strategy to improve photovoltaics performance. However, it is challenging to successfully design and blend multiple donors, while minimizing unfavorable interactions (e.g., morphological traps, recombination centers, etc.). Here, a new Förster resonance energy transfer-based design is shown utilizing the synergistic nature of three light active donors (two small molecules and a high-performance donor–acceptor polymer) with a fullerene acceptor to create highly efficient quaternary PSCs with power conversion efficiencies (PCEs) of up to 10.7%. Within this quaternary architecture, it is revealed that the addition of small molecules in low concentrations broadens the absorption bandwidth, induces cocrystalline molecular conformations, and promotes rapid (picosecond) energy transfer processes. These results provide guidance for the design of multiple-donor systems using simple processing techniques to realize single-junction PSC designs with unprecedented PCEs.

A viable strategy to realize highly efficient quaternary blend solar cells is introduced that breaks efficiency above 10% with complementary squaraine small molecules–low band-gap polymer combinations. Our quaternary design demonstrates several advantages: (i) broader light absorption, (ii) improved surface morphology, (iii) enhanced cocrystallization packing, (iv) multiple energy and charge transfer pathways to reduce recombination, and (v) increased charge mobility.

The process of accurately gauging lifetime improvements in organic photovoltaics (OPVs) or other similar emerging technologies, such as perovskites solar cells is still a major challenge. The presented work is part of a larger effort of developing a worldwide database of lifetimes that can help establishing reference baselines of stability performance for OPVs and other emerging PV technologies, which can then be utilized for pass-fail testing standards and predicting tools. The study constitutes scanning of literature articles related to stability data of OPVs, reported until mid-2015 and collecting the reported data into a database. A generic lifetime marker is utilized for rating the stability of various reported devices. The collected data is combined with an earlier developed and reported database, which was based on articles reported until mid-2013. The extended database is utilized for establishing the baselines of lifetime for OPVs tested under different conditions. The work also provides the recent progress in stability of unencapsulated OPVs with different architectures, as well as presents the updated diagram of the reported record lifetimes of OPVs. The presented work is another step forward towards the development of pass-fail testing standards and lifetime prediction tools for emerging PV technologies.

An extended database of lifetime for organic photovoltaics is presented. The data is utilized for establishing lifetime baselines for the samples tested under different aging conditions. The baselines can serve as a reference for gauging the improvements in device lifetimes in future reports. Encapsulated and unencapsulated samples with the best lifetimes reported in literature so far are listed as well.