In organic photovoltaics, morphological control of donor and acceptor domains on the nanoscale is key for efficient exciton diffusion and dissociation, carrier transport, and suppression of recombination losses. To realise this, here, we demonstrated a double-fibril network based on ternary donor:acceptor morphology with multi-length scales constructed by combining ancillary conjugated polymer crystallizers and non-fullerene acceptor filament assembly. Using this approach, we achieved an average power conversion efficiency of 19.3% (certified 19.2%). The success lies in the good match between the photoelectric parameters and the morphological characteristic lengths, which utilizes the excitons and free charges efficiently. This strategy leads to enhanced exciton diffusion length (hence exciton dissociation yield) and reduced recombination rate, hence minimizing photon-to-electron losses in the ternary devices as compared to their binary counterparts. The double-fibril network morphology strategy minimizes losses and maximizes the power output, offering the possibility towards 20% power conversion efficiencies in single-junction organic photovoltaics. MainOrganic semiconductors offer the advantage of high optical absorption and tunable energy levels, enabling thin-film solar cells with high light-to-electron conversion efficiencies over a wide range of wavelengths [1][2][3][4] . Desipte recent progresses, the performance of organic solar cells (OSCs) is still limited by non-ideal exciton and charge transport, which depend not only on the electronic structure of organic semiconductors but also on the nanostructure that is formed by material crystallization and phase separation in a bulk heterojunction (BHJ) setting [5][6][7][8] . A suitable sized phase-separated morphology that balances crystalline region and mixing domain on the nanoscale is therefore needed to further push the power conversion efficiency (PCE) of OSCs, however it is a

Perovskite compounds have attracted recently great attention in photovoltaic research. The devices are typically fabricated using condensed or mesoporous TiO2 as the electron transport layer and 2,2'7,7'-tetrakis-(N,N-dip-methoxyphenylamine)9,9'-spirobifluorene as the hole transport layer. However, the high-temperature processing (450 °C) requirement of the TiO2 layer could hinder the widespread adoption of the technology. In this report, we adopted a low-temperature processing technique to attain high-efficiency devices in both rigid and flexible substrates, using device structure substrate/ITO/PEDOT:PSS/CH(3)NH(3)PbI(3-x)Cl(x)/PCBM/Al, where PEDOT:PSS and PCBM are used as hole and electron transport layers, respectively. Mixed halide perovskite, CH(3)NH(3)PbI(3-x)Cl(x), was used due to its long carrier lifetime and good electrical properties. All of these layers are solution-processed under 120 °C. Based on the proposed device structure, power conversion efficiency (PCE) of 11.5% is obtained in rigid substrates (glass/ITO), and a 9.2% PCE is achieved for a polyethylene terephthalate/ITO flexible substrate.

The dawn of a new era in optoelectronic technologies has emerged with the recent development of the organic-inorganic hybrid halide perovskite. Its exceptional attributes, including high carrier mobility, an adjustable spectral absorption range, long diffusion lengths, and the simplicity and affordability of fabrication render it one of the most exceptional and market-competitive optoelectronic materials for applications in photovoltaics, light emitting diodes (LED), photodetectors, lasers, and more. Moreover, its versatility in device architecture and ability to achieve relatively high performance devices via various processing techniques makes perovskites a highly promising material for various practical applications. Here, we review the organic-inorganic hybrid halide perovskite and delve into its recent progress and relevant applications. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Tandem solar cells have the potential to improve photon conversion efficiencies (PCEs) beyond the limits of single-junction devices. In this study, a triple-junction tandem design is demonstrated by employing three distinct organic donor materials having bandgap energies ranging from 1.4 to 1.9 eV. Through optical modeling, balanced photon absorption rates are achieved and, thereby, the photo-currents are matched among the three subcells. Accordingly, an efficient triple-junction tandem organic solar cell can exhibit a record-high PCE of 11.5%.

Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons. The top transparent electrode employs a highly transparent silver nanowire-metal oxide composite conducting film, which is coated through mild solution processes. With this combination, we have achieved 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells. The optimized devices have a maximum transparency of 66% at 550 nm.

The tandem solar cell architecture is an effective way to harvest a broader part of the solar spectrum and make better use of the photonic energy than the single junction cell. Here, we present the design, synthesis, and characterization of a series of new low bandgap polymers specifically for tandem polymer solar cells. These polymers have a backbone based on the benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) units. Alkylthienyl and alkylphenyl moieties were incorporated onto the BDT unit to form BDTT and BDTP units, respectively; a furan moiety was incorporated onto the DPP unit in place of thiophene to form the FDPP unit. Low bandgap polymers (bandgap = 1.4-1.5 eV) were prepared using BDTT, BDTP, FDPP, and DPP units via Stille-coupling polymerization. These structural modifications lead to polymers with different optical, electrochemical, and electronic properties. Single junction solar cells were fabricated, and the polymer:PC(71)BM active layer morphology was optimized by adding 1,8-diiodooctane (DIO) as an additive. In the single-layer photovoltaic device, they showed power conversion efficiencies (PCEs) of 3-6%. When the polymers were applied in tandem solar cells, PCEs over 8% were reached, demonstrating their great potential for high efficiency tandem polymer solar cells.

A reduction of the bandgap and an enhancement of the charge transport properties of a LBG polymer (PBDTT‐DPP) can be achieved simultaneously by changing the sulfur atoms on the DPP unit to selenium atoms. The newly designed polymer, PBDTT‐SeDPP (Eg = 1.38 eV), shows excellent photovoltaic performance in single junction devices with power conversion efficiencies (PCEs) over 7% and photo‐response up to 900 nm. A tandem polymer solar cell and a visibly transparent solar cell based on PBDTT‐SeDPP show 9.5% and 4.5% PCEs, which are superior to those based on PBDTT‐DPP.

Formamidinium (FA)-based perovskite materials show an extended absorption spectrum to 840 nm, which enables high power conversion efficiencies of over 20% compared with normal-structure perovskite solar cells (PSCs).