Billy

Abstract

A new electron-rich central building block, 5,5,12,12-tetrakis(4-hexylphenyl)-indacenobis-(dithieno[3,2-b:2′,3′-d]pyrrol) (INP), and two derivative nonfullerene acceptors (INPIC and INPIC-4F) are designed and synthesized. The two molecules reveal broad (600–900 nm) and strong absorption due to the satisfactory electron-donating ability of INP. Compared with its counterpart INPIC, fluorinated nonfullerene acceptor INPIC-4F exhibits a stronger near-infrared absorption with a narrower optical bandgap of 1.39 eV, an improved crystallinity with higher electron mobility, and down-shifted highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. Organic solar cells (OSCs) based on INPIC-4F exhibit a high power conversion efficiency (PCE) of 13.13% and a relatively low energy loss of 0.54 eV, which is among the highest efficiencies reported for binary OSCs in the literature. The results demonstrate the great potential of the new INP as an electron-donating building block for constructing high-performance nonfullerene acceptors for OSCs.

Nonfullerene acceptors (NFAs) featuring indacenobis-(dithieno[3,2-b:2′,3′-d]pyrrol) as an electron-rich central building block are designed. The NFAs extend absorption to 900 nm with an optical bandgap of 1.39 eV. Organic solar cells (OSCs), by blending with PBDB-T as polymer donor, contribute a power conversion efficiency of 13.13%, which is among the highest reported for binary OSCs in the literature.

Limited by the various inherent energy losses from multiple channels, organic solar cells show inferior device performance compared to traditional inorganic photovoltaic techniques, such as silicon and CuInGaSe. To alleviate these fundamental limitations, an integrated multiple strategy is implemented including molecular design, interfacial engineering, optical manipulation, and tandem device construction into one cell. Considering the close correlation among these loss channels, a sophisticated quantification of energy-loss reduction is tracked along with each strategy in a perspective to reach rational overall optimum. A novel nonfullerene acceptor, 6TBA, is synthesized to resolve the thermalization and V_OC loss, and another small bandgap nonfullerene acceptor, 4TIC, is used in the back sub-cell to alleviate transmission loss. Tandem architecture design significantly reduces the light absorption loss, and compensates carrier dynamics and thermalization loss. Interfacial engineering further reduces energy loss from carrier dynamics in the tandem architecture. As a result of this concerted effort, a very high power conversion efficiency (13.20%) is obtained. A detailed quantitative analysis on the energy losses confirms that the improved device performance stems from these multiple strategies. The results provide a rational way to explore the ultimate device performance through molecular design and device engineering.

Comprehensive optimization on organic solar cells is conducted, including molecular design, interfacial engineering, optical manipulation, and tandem architecture construction. Synergistical application of multiple strategies improves the balance of the energy losses from transmission, insufficient light trapping, thermalization, and carrier dynamic loss. An impressively high device performance up to 13.2% is achieved.

Besides broadening of the absorption spectrum, modulating molecular energy levels, and other well-studied properties, a stronger intramolecular electron push–pull effect also affords other advantages in nonfullerene acceptors. A strong push–pull effect improves the dipole moment of the wings in IT-4F over IT-M and results in a lower miscibility than IT-M when blended with PBDB-TF. This feature leads to higher domain purity in the PBDB-TF:IT-4F blend and makes a contribution to the better photovoltaic performance. Moreover, the strong push–pull effect also decreases the vibrational relaxation, which makes IT-4F more promising than IT-M in reducing the energetic loss of organic solar cells. Above all, a power conversion efficiency of 13.7% is recorded in PBDB-TF:IT-4F-based devices.

Two critical factors (miscibility and vibrational relaxation) of nonfullerene molecular acceptors with the intramolecular electron push–pull effect are analyzed and related to their photovoltaic properties in organic solar cells (OSCs). A power conversion efficiency of 13.7% is recorded in OSCs by using a nonfullerene acceptor IT-4F, which shows a stronger intramolecular electron push–pull effect than its nonfluorinated counterpart.

In order to utilize the near-infrared (NIR) solar photons like silicon-based solar cells, extensive research efforts have been devoted to the development of organic donor and acceptor materials with strong NIR absorption. However, single-junction organic solar cells (OSCs) with photoresponse extending into >1000 nm and power conversion efficiency (PCE) >11% have rarely been reported. Herein, three fused-ring electron acceptors with varying core size are reported. These three molecules exhibit strong absorption from 600 to 1000 nm and high electron mobility (>1 × 10⁻³ cm² V⁻¹ s⁻¹). It is proposed that core engineering is a promising approach to elevate energy levels, enhance absorption and electron mobility, and finally achieve high device performance. This approach can maximize both short-circuit current density (  J_SC) and open-circuit voltage (V_OC) at the same time, differing from the commonly used end group engineering that is generally unable to realize simultaneous enhancement in both V_OC and J_SC. Finally, the single-junction OSCs based on these acceptors in combination with the widely polymer donor PTB7-Th yield J_SC as high as 26.00 mA cm⁻² and PCE as high as 12.3%.

Single-junction binary-blend polymer solar cells based on PTB7-Th/F8IC afford efficiency of 10.9%, which is higher than those of F6IC (7.1%) and F10IC (10.2%) counterparts. Furthermore, ternary-blend devices based on PTB7-Th/F8IC/PC₇₁BM exhibit J_SC as high as 26.00 mA cm⁻² and power conversion efficiency as high as 12.3%.

Relative to electron donors for bulk heterojunction organic solar cells (OSCs), electron acceptors that absorb strongly in the visible and even near-infrared region are less well developed, which hinders the further development of OSCs. Fullerenes as traditional electron acceptors have relatively weak visible absorption and limited electronic tunability, which constrains the optical and electronic properties required of the donor. Here, high-performance fullerene-free OSCs based on a combination of a medium-bandgap polymer donor (FTAZ) and a narrow-bandgap nonfullerene acceptor (IDIC), which exhibit complementary absorption, matched energy levels, and blend with pure phases on the exciton diffusion length scale, are reported. The single-junction OSCs based on the FTAZ:IDIC blend exhibit power conversion efficiencies up to 12.5% with a certified value of 12.14%. Transient absorption spectroscopy reveals that exciting either the donor or the acceptor component efficiently generates mobile charges, which do not suffer from recombination to triplet states. Balancing photocurrent generation between the donor and nonfullerene acceptor removes undesirable constraints on the donor imposed by fullerene derivatives, opening a new avenue toward even higher efficiency for OSCs.

High-performance fullerene-free single-junction organic solar cells with power conversion efficiencies up to 12.5% are reported. Transient absorption spectroscopy reveals that exciting either the donor or acceptor component efficiently generates mobile charges, which do not suffer from recombination to triplet states.

In article number 1701405, Hae Jung Son and co-workers develop D₁-A-D₂-A-type random terpolymers. Organic photovoltaics (OPVs) introducing the resulting polymer achieve a high efficiency of 10.31%. Furthermore, due to outstanding solution processability of the random terpolymer, 1 cm² OPVs reproducibly shows a high efficiency of up to 9.42% using thick active layers in the range of 250–380 nm.

An all-acceptor homopolymer is synthesized by Xugang Guo and co-workers, as described in article number 1705745, using a novel electron-deficient thiazole imide, which enables high-performance unipolar n-type organic thin-film transistors with a remarkable electron mobility (1.6 cm² V⁻¹ s⁻¹). The superior transistor performance demonstrates that the all-acceptor approach is highly promising in constructing intrinsic n-type organic semiconductors.

Well-balanced ambipolar conjugated polymers with mild glass-transition temperatures are developed by Weifeng Zhang, Gui Yu, and co-workers in article number 1705286. High-performance flexible field-effect transistors (PFETs) based on these polymers exhibit high and well-balanced hole/electron mobilities of 5.97/7.07 cm² V⁻¹ s⁻¹ under ambient conditions. Meanwhile, flexible complementarylike inverters also afford a very high gain of 148.

Solution-based processing of materials for electrical doping of organic semiconductor interfaces is attractive for boosting the efficiency of organic electronic devices with multilayer structures. To simplify this process, self-doping perylene diimide (PDI)-based ionene polymers are synthesized, in which the semiconductor PDI components are embedded together with electrolyte dopants in the polymer backbone. Functionality contained within the PDI monomers suppresses their aggregation, affording self-doping interlayers with controllable thickness when processed from solution into organic photovoltaic devices (OPVs). Optimal results for interfacial self-doping lead to increased power conversion efficiencies (PCEs) of the fullerene-based OPVs, from 2.62% to 10.64%, and of the nonfullerene-based OPVs, from 3.34% to 10.59%. These PDI–ionene interlayers enable chemical and morphological control of interfacial doping and conductivity, demonstrating that the conductive channels are crucial for charge transport in doped organic semiconductor films. Using these novel interlayers with efficient doping and high conductivity, both fullerene- and nonfullerene-based OPVs are achieved with PCEs exceeding 9% over interlayer thicknesses ranging from ≈3 to 40 nm.

Self-doping of perylene-diimide-based ionenes enables chemical and morphological control of interfacial doping and conductivity in organic electronic devices. Using these materials provides a straightforward and controllable method to modulate the interface between electrodes and active layers, affording both fullerene- and nonfullerene-based solar cells with high efficiencies over a wide range of doped interlayer thicknesses.

Molecular weight is an important factor determining the morphology and performance of all-polymer solar cells. Through the application of direct arylation polycondention, a series of batches of a fluorinated naphthalene diimide-based acceptor polymer are prepared with molecular weight varying from M_n = 20 to 167 kDa. Used in conjunction with a common low bandgap donor polymer, the effect of acceptor molecular weight on solar cell performance, morphology, charge generation, and transport is explored. Increasing the molecular weight of the acceptor from M_n = 20 to 87 kDa is found to increase cell efficiency from 2.3% to 5.4% due to improved charge separation and transport. Further increasing the molecular weight to M_n = 167 kDa however is found to produce a drop in performance to 3% due to liquid–liquid phase separation which produces coarse domains, poor charge generation, and collection. In addition to device studies, a systematic investigation of the microstructure and photophysics of this system is presented using a combination of transmission electron microscopy, grazing-incidence wide-angle X-ray scattering, near-edge X-ray absorption fine-structure spectroscopy, photoluminescence quenching, and transient absorption spectroscopy to provide a comprehensive understanding of the interplay between morphology, photophysics, and photovoltaic performance.

Excessively high molecular weights are shown to be detrimental to the performance of all-polymer solar cells. Increasing the molecular weight of the acceptor polymer to M_n = 167 kDa is found to result in liquid–liquid phase separation negatively impacting charge generation and collection. Intermediate molecular weights instead provide an optimum morphology with good carrier mobilities and improved molecular order.

Two wide bandgap star-shaped small molecular acceptors, para-TrBRCN and meta-TrBRCN, are synthesized for efficient nonfullerene polymer solar cells (PSCs). The tiny structural variation by just changing the linkage positions affects largely the inherent properties of the resulting molecules. Both molecules have a nonplanar 3D structure, which can prevent the excessively aggregation to realize the optimized morphology and ideal domain size in their active blends. Compared to para-TrBRCN, meta-TrBRCN exhibits the smaller distortions between the truxene skeleton and the benzothiadiazole units, which would also lead to the enhanced π–π stacking and charge transfer. When blending with PTB7-Th, high power conversion efficiencies (PCEs) of 10.15% and 8.28% are obtained for meta-TrBRCN and para-TrBRCN devices, respectively. To make up the weak absorption of above binary active blend in the longer wavelength region and increase the whole device performance further, low bandgap 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylthienyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (ITIC-Th) is added as the second acceptor material to fabricate ternary blend PSCs. After adding 20 wt% of ITIC-Th, the resulting devices exhibit the well-balanced optical absorption and fine-tuned morphology, giving rise to the significantly improved PCE of 11.40% with much higher J _sc of 18.25 mA cm⁻² and fill factor of 70.2%.

Tow star-shaped wide bandgap molecular acceptors with truxene core were synthesized for efficient non-fullerene polymer solar cells. Both acceptors show high absorptions in the short wavelength region, which can match well with those of low bandgap polymer donors, giving rise to high power conversion efficiencies of 10.15% from binary blend devices and 11.40% from ternary blend devices, respectively.

Optimizing the interfacial contacts between the photoactive layer and the electrodes is an important factor in determining the performance of organic solar cells (OSCs). A charge-selective layer with tailored electrical properties enhances the charge collection efficiency and interfacial stability. Here, the potential of hydrogenated TiO₂ nanoparticles (H-TiO₂ NPs) as an efficient electron-selective layer (ESL) material in OSCs is reported for the first time. The H-TiO₂ is synthesized by discharge plasma in liquid at atmospheric pressure, which has the benefits of a simple one-pot synthesis process, rapid and mild reaction conditions, and the capacity for mass production. The H-TiO₂ exhibits high conductivity and favorable energy level formation for efficient electron extraction, providing a basis for an efficient bilayer ESL system composed of conjugated polyelectrolyte/H-TiO₂. Thus, the enhanced charge transport and extraction efficiency with reduced recombination losses at the cathode interfacial contacts is achieved. Moreover, the OSCs composed of H-TiO₂ are almost free of light soaking, which has been reported to severely limit the performance and stability of OSCs based on conventional TiO₂ ESLs. Therefore, H-TiO₂ as a new efficient, stable, and cost-effective ESL material has the potential to open new opportunities for optoelectronic devices.

This study demonstrates the potential of hydrogenated TiO₂ (H-TiO₂) as an efficient electron-selective layer in optoelectronic devices. The H-TiO₂ is simply one-pot mass-produced using a discharge plasma system in liquid at atmospheric pressure. The H-TiO₂ exhibits high conductivity and favorable energy level formation, resulting in the high-efficiency and light-soaking-free organic solar cells.

Three acceptor–donor–acceptor type nonfullerene acceptors (NFAs), namely, F–F, F–Cl, and F–Br, are designed and synthesized through a halogenation strategy on one successful nonfullerene acceptor FDICTF (F–H). The three molecules show red-shifted absorptions, increased crystallinities, and higher charge mobilities compared with the F–H. After blending with donor polymer PBDB-T, the F–F-, F–Cl-, and F–Br-based devices exhibit power conversion efficiencies (PCEs) of 10.85%, 11.47%, and 12.05%, respectively, which are higher than that of F–H with PCE of 9.59%. These results indicate that manipulating the absorption range, crystallinity and mobilities of NFAs by introducing different halogen atoms is an effective way to achieve high photovoltaic performance, which will offer valuable insight for the designing of high-efficiency organic solar cells.

Through a halogenation strategy onto the end-capping group in the FDICTF-based small-molecule acceptor, red-shifted absorptions, increased crystallinities, and higher charge mobilities are achieved. The device based on F–Br with power conversion efficiency of 12.05% and remarkable FF of 76% is one of only a few organic solar cells with efficiencies over 12% reported to date.

Polymer solar cells (PSCs) continue to be a promising low-cost and lead-free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X-ray microscopy method, the temperature dependences of “molecular miscibility” in the presence of fullerene crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high-efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, an approach is outlined to convert liquidus miscibility to an effective Flory–Huggins interaction parameter χ. Crucially, determination of temperature-dependent amorphous miscibility paves a way to rationally optimize the stability and mixing behaviors of PSCs at actual processing and operating temperatures.

The significance of miscibility and its temperature dependence in controlling morphology, performance, and stability of polymer:fullerene solar cells is discussed. Highly variable miscibility is observed for a wide range of systems and can be converted to temperature-dependent effective Flory–Huggins interaction parameter (χ). There is an optimum miscibility near the fullerene percolation threshold for the most efficient and stable solar cells.

In the field of organic solar cells (OSCs), tandem structure devices exhibit very attractive advantages for improving power conversion efficiency (PCE). In addition to the well researched novel pair of active layers in different subcells, the construction of interconnecting layer (ICL) also plays a critical role in achieving high performance tandem devices. In this work, a new way of achieving environmentally friendly solvent processed polymeric ICL by adopting poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-5,5′-bis(2,2′-thiophene)-2,6-naphthalene-1,4,5,8-tetracaboxylic-N,N′-di(2-ethylhexyl)imide] (PNDIT-F3N) blended with poly(ethyleneimine) (PEI) as the electron transport layer (ETL) and PEDOT:PSS as the hole transport layer is reported. It is found that the modification ability of PNDIT-F3N on PEDOT can be linearly tuned by the incorporation of PEI, which offers the opportunity to study the charge recombination behavior in ICL. At last, tandem OSC with highest PCE of 12.6% is achieved, which is one of the best tandem OSCs reported till now. These results offer a new selection for constructing efficient ICL in high performance tandem OSCs and guide the way of design new ETL materials for ICL construction, and may even be integrated in future printed flexible large area module device fabrication with the advantages of environmentally friendly solvent processing and thickness insensitivity.

A new polymeric interconnecting layer (ICL) based on poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-5,5′-bis(2,2′-thiophene)-2,6-naphthalene-1,4,5,8-tetracaboxylic-N,N′-di(2-ethylhexyl)imide]: poly(ethyleneimine)/PEDOT:PSS is developed and applied for the fabrication of high performance tandem organic solar cells (OSCs). Tandem OSCs employing this ICL achieve a high power conversion efficiency of 12.6% with ICL thickness of 60 nm and even reach to 11.3% with ICL thickness of 140 nm.

A novel wide-bandgap electron-donating copolymer containing an electron-deficient, difluorobenzotriazole building block with a siloxane-terminated side chain is developed. The resulting polymer, poly{(4,8-bis(4,5-dihexylthiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-co-4,7-di(thiophen-2-yl)-5,6-difluoro-2-(6-(1,1,1,3,5,5,5-heptamethyltri-siloxan-3-yl)hexyl)-2H-benzo[d][1,2,3]triazole} (PBTA-Si), is used to successfully fabricate high-performance, ternary, all-polymer solar cells (all-PSCs) insensitive to the active layer thickness. An impressively high fill factor of ≈76% is achieved with various ternary-blending ratios. The optimized all-PSCs attain a power conversion efficiency (PCE) of 9.17% with an active layer thickness of 350 nm and maintain a PCE over 8% for thicknesses over 400 nm, which is the highest reported efficiency for thick all-PSCs. These results can be attributed to efficient charge transfer, additional energy transfer, high and balanced charge transport, and weak recombination behavior in the photoactive layer. Moreover, the photoactive layers of the ternary all-PSCs are processed in a nonhalogenated solvent, 2-methyltetrahydrofuran, which greatly improves their compatibility with large-scale manufacturing.

A novel electron-donating copolymer, PBTA-Si, containing a benzotriazole building block with a siloxane-functionalized side chain, is developed and used to fabricate thick-film all-polymer solar cells (all-PSC). By means of ternary blending, the all-PSCs attain a power conversion efficiency of 9.17% with a 350 nm thick active layer and 8.34% with a thickness of 420 nm.

A new naphthalene diimide (NDI)-based polymer with strong electron withdrawing dicyanothiophene (P(NDI2DT-TTCN)) is developed as the electron transport layer (ETL) in place of the fullerene-based ETL in inverted perovskite solar cells (Pero-SCs). A combination of characterization techniques, including atomic force microscopy, scanning electron microscopy, grazing-incidence wide-angle X-ray scattering, near-edge X-ray absorption fine-structure spectroscopy, space-charge-limited current, electrochemical impedance spectroscopy, photoluminescence (PL), and time-resolved PL decay, is used to demonstrate the interface phenomena between perovskite and P(NDI2DT-TTCN) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). It is found that P(NDI2DT-TTCN) not only improves the electron extraction ability but also prevents ambient condition interference by forming a hydrophobic ETL surface. In addition, P(NDI2DT-TTCN) has excellent mechanical stability compared to PCBM in flexible Pero-SCs. With these improved functionalities, the performance of devices based on P(NDI2DT-TTCN) significantly outperform those based on PCBM from 14.3 to 17.0%, which is the highest photovoltaic performance with negligible hysteresis in the field of polymeric ETLs.

A novel naphthalene diimide (NDI)-based polymer (P(NDI2DT-TTCN)) is used as the electron transport layer in inverted flexible perovskite solar cells. Photovoltaic performances of the P(NDI2DT-TTCN)-based device show a significant improvement up to 17.0%, whereas the control device for [6,6]-phenyl-C61-butyric acid methyl ester based device only shows power conversion efficiency of 14.3%. In addition, P(NDI2DT-TTCN) improves not only the light-induced and long-term stability but also mechanical stability.

Heterojunctions of carbon nanotubes interfaced with silicon respond to light illumination and can be operated in the power regime as solar cells. Very significant advances have been made in the last 5 years both in terms of headline performance values and in fundamental understanding of the underlying operating principles, as well as the sophistication of the devices and studies being reported. The body of literature is growing rapidly, and the latest power conversion efficiency and active area records have now reached over 17% and 2 cm², respectively. Thus, the authors believe that it is now a useful time for an evaluation of the current state-of-the-art and challenges going forward, as well as for a comprehensively updated review of progress made in the field. In addition, the authors provide a summary of the various fabrication schemes that have been used, analysis of some of the major device structure–property relationships revealed by comparison of published works, and a thorough breakdown of the various factors involved in improving performance, as well as a critical assessment of the real opportunities that may exist for this technology in the context of the wider silicon photovoltaics industry.

The significant progress that has been made in improving the performance and stability of carbon nanotube–silicon heterojunction solar cells, and in understanding of the operating principles, is discussed. In addition, a comprehensive review of the literature, a roadmap for future performance improvement, and a critical assessment of the opportunities for this rapidly developing field in the wider context of the silicon photovoltaics industry are provided.

In this report, highly efficient and humidity-resistant perovskite solar cells (PSCs) using two new small molecule hole transporting materials (HTM) made from a cost-effective precursor anthanthrone (ANT) dye, namely, 4,10-bis(1,2-dihydroacenaphthylen-5-yl)-6,12-bis(octyloxy)-6,12-dihydronaphtho[7,8,1,2,3-nopqr]tetraphene (ACE-ANT-ACE) and 4,4′-(6,12-bis(octyloxy)-6,12-dihydronaphtho[7,8,1,2,3-nopqr]tetraphene-4,10-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TPA-ANT-TPA) are presented. The newly developed HTMs are systematically compared with the conventional 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamino)-9,9′-spirbiuorene (Spiro-OMeTAD). ACE-ANT-ACE and TPA-ANT-TPA are used as a dopant-free HTM in mesoscopic TiO₂/CH₃NH₃PbI₃/HTM solid-state PSCs, and the performance as well as stability are compared with Spiro-OMeTAD-based PSCs. After extensive optimization of the metal oxide scaffold and device processing conditions, dopant-free novel TPA-ANT-TPA HTM-based PSC devices achieve a maximum power conversion efficiency (PCE) of 17.5% with negligible hysteresis. An impressive current of 21 mA cm⁻² is also confirmed from photocurrent density with a higher fill factor of 0.79. The obtained PCE of 17.5% utilizing TPA-ANT-TPA is higher performance than the devices prepared using doped Spiro-OMeTAD (16.8%) as hole transport layer at 1 sun condition. It is found that doping of LiTFSI salt increases hygroscopic characteristics in Spiro-OMeTAD; this leads to the fast degradation of solar cells. While, solar cells prepared using undoped TPA-ANT-TPA show dewetting and improved stability. Additionally, the new HTMs form a fully homogeneous and completely covering thin film on the surface of the active light absorbing perovskite layers that acts as a protective coating for underlying perovskite films. This breakthrough paves the way for development of new inexpensive, more stable, and highly efficient ANT core based lower cost HTMs for cost-effective, conventional, and printable PSCs.

First time low-cost anthanthrone dye based hole transporting materials (HTMs) 4,10-bis(1,2-dihydroacenaphthylen-5-yl)-6,12-bis(octyloxy)-6,12-dihydronaphtho[7,8,1,2,3-nopqr]tetraphene (ACE-ANT-ACE) and 4,4′-(6,12-bis(octyloxy)-6,12-dihydronaphtho[7,8,1,2,3-nopqr]tetraphene-4,10-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TPA-ANT-TPA) end capped with dihydroacenaphthylene and triphenyleamine groups are designed and synthesized, respectively. Among both, dopant-free TPA-ANT-TPA cut-rate HTM ($67 g⁻¹) exhibits higher performance with 17.5% efficiency and retains respectable performance after 50 h in 58% relative humidity than conventional expensive 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamino)-9,9′-spirbiuorene.

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution-processable hole-transport layer (HTL) material in transistors, organic light-emitting diodes, and solar cells are reported. Density-functional theory calculations combined with X-ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution-processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at −5.1 eV. Hole-transport analysis performed using field-effect measurements confirms the p-type character of CuSeCN yielding a hole mobility of 0.002 cm² V⁻¹ s⁻¹. When CuSeCN is incorporated as the HTL material in organic light-emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4-ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.

Copper (I) selenocyanate is successfully synthesized, studied, and applied as a wide bandgap hole-transporting material in transistors, organic solar cells, and light-emitting diodes, for the first time. Resulting devices exhibit excellent operating characteristics highlighting the tremendous potential of metal pseudohalides as a new class of highly transparent p-type semiconductors.

In article 1703398, Jong-Hong Lu, Chih-Ping Chen and, co-workers demonstrate a Ag/ITO/Ag based microcavity (MC) structure for colorful organic photovoltaics applications. OPVs with an ultra-wide vivid color-gamut (blue, green, yellow-green, yellow, orange, and red), with PCEs as high as 8.2% for the yellow-green [CIE 1931: (0.364, 0.542)] device with a highest transmittance of 17.3% at 561 nm are demonstrated.

Hole transport layer (HTL) plays a critical role for achieving high performance solution-processed optoelectronics including organic electronics. For organic solar cells (OSCs), the inverted structure has been widely adopted to achieve prolonged stability. However, there are limited studies of p-type effective HTL on top of the organic active layer (hereafter named as top HTL) for inverted OSCs. Currently, p-type top HTLs are mainly 2D materials, which have an intrinsic vertical conduction limitation and are too thin to function as practical HTL for large area optoelectronic applications. In the present study, a novel self-assembled quasi-3D nanocomposite is demonstrated as a p-type top HTL. Remarkably, the novel HTL achieves ≈15 times enhanced conductivity and ≈16 times extended thickness compared to the 2D counterpart. By applying this novel HTL in inverted OSCs covering fullerene and non-fullerene systems, device performance is significantly improved. The champion power conversion efficiency reaches 12.13%, which is the highest reported performance of solution processed HTL based inverted OSCs. Furthermore, the stability of OSCs is dramatically enhanced compared with conventional devices. The work contributes to not only evolving the highly stable and large scale OSCs for practical applications but also diversifying the strategies to improve device performance.

A novel self-assembled quasi-3D nanocomposite is demonstrated to be an effective top hole transport layer (HTL) for both fullerene and non-fullerene inverted organic solar cells. Due to the better conductivity of this nanocomposite HTL, the thickness sensitivity issue of graphene oxide is addressed. Surface recombination is suppressed and the highest power conversion efficiency can reach 12.13%.

Two new wide-bandgap D–A–π copolymer donor materials, PBDT-2TC and PBDT-S-2TC, based on benzodithiophene and asymmetric bithiophene with one carboxylate (2TC) substituent are synthesized by a facile approach for fullerene-free organic solar cells (OSCs). The combination of one carboxylate-substituted thiophene with one thiophene bridge in the backbone substantially reduces the steric hindrance, thereby favoring a planar geometry for efficient charge transport and molecular packing. A reasonable highest-occupied-molecular-orbital energy level in relation to that of the acceptor and balanced hole and electron transport are observed for both polymers. This asymmetric structure unit is flexible and versatile, allowing the absorption, energy levels, and morphology of the blend films to be tailored. Fullerene-free OSCs based on PBDT-S-2TC:ITIC achieve a high power conversion efficiency of 10.12%. More impressively, a successful nonhalogen solvent-processed solar cell with 9.55% efficiency is also achieved, which is one of the highest values for a fullerene-free OSC processed using an ecofriendly solvent.

New wide-bandgap D–A–π copolymers based on an asymmetric bithiophene with one carboxylate substituent were synthesized. The asymmetric structure unit is flexible and versatile, which allows the absorption, energy levels and morphology of the blend films to be adjusted easily. D-A-p copolymers produced a high power conversion efficiency of 10.0% for halogen solvent-processed OSCs and 9.55% for non-halogen solvent-processed devices.

Realizing over 10% efficiency in printed organic solar cells via scalable materials and less toxic solvents remains a grand challenge. In article number 1705485, Harald Ade and co-workers report chlorine-free, in-air blade-coating of a new photoactive combination, FTAZ:IT-M, which is able to yield an efficiency of nearly 11%, despite a high humidity of ≈50%.

The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point-of-care testing. The technology exploits devices that can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics can potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food-compatible electronic tags that can “smart” track goods and monitor their quality along the distribution chain. Temporary tattoo-paper is hereby proposed as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, the fabrication of all-printed organic field-effect transistors on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex nonplanar geometry is demonstrated.

Temporary tattoo-paper is proposed as a simple and versatile platform for the integration of biocompatible organic electronics onto food and pharmaceutical capsules. The fabrication of all-printed biocompatible organic transistors and complementary logic on untreated commercial tattoo-paper, and their subsequent transfer to and operation on edible substrates is demonstrated, paving the way for novel point-of-care devices and smart food labels.