Mahui

A series of novel carbazole‐triphenylamine hole transporting materials with a pyridine or benzene on the N of the carbazole unit have been designed and synthesized. Due to the passivation function of the pyridine unit, a higher power conversion efficiency and better stability are achieved when the pyridine‐contained molecule is used in perovskite solar cells.

Four carbazole‐triphenylamine hole transporting materials (HTMs) with a pyridine or benzene on the N of carbazole have been designed and developed. The molecular structures on their photophysical, electrochemical, thermal, as well as photovoltaic properties in perovskite solar cells (PSCs) are comprehensively analyzed. It is noted that the pyridine‐contained compounds show bathochromic spectra response, slightly lower HOMO level, and higher thermal stability than their benzene‐contained counterparts. Photoluminescence study indicates that the molecule with a pyridine unit possess better hole extraction properties on the perovskite/HTM interface. When used in PSCs, pyridine‐contained HTMs exhibit higher efficiency and better stability than benzene‐contained HTMs. Moreover, the PSCs based on the pyridine‐contained HTM exhibit a promising power conversion efficiency of 18.45% with good light‐soaking and long‐term stability, which is even better than that of conventional spiro‐OMeTAD under the same conditions. Therefore, the results provide a promising strategy to design and develop novel HTM molecules for efficient and stable PSCs.

A bifunctional saddle‐shaped small molecule α, β‐COTh‐Ph‐OMeTAD is synthesized and systemically charactered as a dopant‐free hole transporting material and interfacial layer in perovskite solar cells (PSCs). A higher power conversion efficiency (PCE) (17.22%) and stable‐enhanced PSCs devices are achieved when compared with that based on spiro‐OMeTAD (16.66%). Noteworthily, after storing nearly for 800 h, 86% of the maximum PCE is retained without any encapsulation.

Herein, a new bifunctional saddle‐shaped organic small molecule named 2,2′,7,7′‐tetrakis(N, N‐di‐p‐methoxyphenyl‐aniline)‐α, β‐cycloocta[1,2‐b:4,3‐b′:5,6‐b′:8,7‐b″′]tetrathiophenyl (α, β‐COTh‐Ph‐OMeTAD) is synthesized. When compared with spiro‐OMeTAD, a star hole transporting material (HTM) for highly efficient perovskite solar cells, the new material has a deeper highest occupied molecular orbital (HOMO) energy level of −5.30 eV, and a higher hole mobility of 2.88 × 10⁻⁴ cm² V⁻¹ s⁻¹. With dopant‐free α, β‐COTh‐Ph‐OMeTAD as a HTM and an interfacial layer combinined with chlorobenzene (CB) as the anti‐solvent, mesoporous perovskite solar cells (PSCs) are fabricated, which exhibit a power conversion efficiency (PCE) of 17.22% under AM 1.5 conditions, which is a little higher than that of devices based‐on doped spiro‐OMeTAD under the same conditions, which is 16.83%. Notably, the PSCs devices with dopant‐free α, β‐COTh‐Ph‐OMeTAD as both the HTM and interfacial layer show better stability, and after being stored in dark and dry air without encapsulation for nearly 800 h, the PCE can still be maintained at 86% of the maximum. This opens a new avenue for efficient and stable PSCs by exploring new dopant‐free materials as alternatives to spiro‐OMeTAD.

Employing an electron‐deficient‐core‐based fused structure instead of a fused donor unit represents a new strategy to adjust the optoelectronic properties of acceptor–donor–acceptor‐type n‐type organic semiconductors. The electron‐deficient‐core based on benzothiadiazole together with dicyanomethylene derivative realizes a low bandgap, high electron mobility, and suitable energy level simultaneously, affording universal and high performances when blending with different donor polymers.

Abstract

Narrow bandgap n‐type organic semiconductors (n‐OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n‐OS acceptor, Y5, with an electron‐deficient‐core‐based fused structure is designed and synthesized, which exhibits a strong absorption in the 600–900 nm region with an extinction coefficient of 1.24 × 10⁵ cm⁻¹, and an electron mobility of 2.11 × 10⁻⁴ cm² V⁻¹ s⁻¹. By blending Y5 with three types of common medium‐bandgap polymers (J61, PBDB‐T, and TTFQx‐T1) as donors, all devices exhibit high short‐circuit current densities over 20 mA cm⁻². As a result, the power conversion efficiency of the Y5‐based OSCs with J61, TTFQx‐T1, and PBDB‐T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n‐OS acceptor for applications in organic solar cells.

A highly efficient, stable, and ductile nonfullerene ternary organic solar cell by integrating two polymer donors and one acceptor is achieved. The enhanced performance and stability are mainly attributed to the suppressed crystallization of the nonfullerene acceptor by introducing a stiff donor that shows low miscibility with the acceptor and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer.

Abstract

Organic solar cells (OSCs) are one of the most promising cost‐effective options for utilizing solar energy, and, while the field of OSCs has progressed rapidly in device performance in the past few years, the stability of nonfullerene OSCs has received less attention. Developing devices with both high performance and long‐term stability remains challenging, particularly if the material choice is restricted by roll‐to‐roll and benign solvent processing requirements and desirable mechanical durability. Building upon the ink (toluene:FTAZ:IT‐M) that broke the 10% benchmark when blade‐coated in air, a second donor material (PBDB‐T) is introduced to stabilize and enhance performance with power conversion efficiency over 13% while keeping toluene as the solvent. More importantly, the ternary OSCs exhibit excellent thermal stability and storage stability while retaining high ductility. The excellent performance and stability are mainly attributed to the inhibition of the crystallization of nonfullerene small‐molecular acceptors (SMAs) by introducing a stiff donor that also shows low miscibility with the nonfullerene SMA and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer. The study indicates that improved stability and performance can be achieved in a synergistic way without significant embrittlement, which will accelerate the future development and application of nonfullerene OSCs.

An effective but simple approach to rationally tune the crystallinity and miscibility of small‐molecular acceptors is reported. With a phenyl introduced at the tail of alkyl side chains, the morphology and molecular orientations of heterojunction are greatly improved. Outstanding efficiencies of 13.23% and 14.04% are detected from the as‐cast and annealed devices, promoted by the fairly high fill factors.

Abstract

Research on fused‐ring small‐molecular‐acceptors (SMAs) has deeply advanced the development of organic solar cells (OSCs). Compared to fruitful studies of ladder‐type cores and end‐caps of SMAs, the exploration of side chains is monotonous. The widely utilized alkyl and aryl side chains usually produce a conflicting association between SMAs' crystallinity and miscibility. Herein, a fresh idea about the modification of side chains is reported to explore the subtle balance between the crystallinity and miscibility. Specifically, a phenyl is introduced to the tail of the alkyl side chain whereby a new acceptor IDIC‐C4Ph is reported. Moderately weakened crystallinity is observed, while maintaining preferred absorption profiles and face‐on orientations. Concurrently, remarkably improved heterojunction morphologies and stacking orientations are detected. PBDB‐T:IDIC‐C4Ph devices exhibit greater efficiency of 11.50% than devices from alky and aryl modified acceptors. Notably, the as‐cast OSCs of PBDB‐TF:IDIC‐C4Ph reveal outstanding FF over 76% with the best efficiency up to 13.23%. The annealed devices reveal further increased efficiency exceeding 14% with the state of the art FF of 78.32%. Overall, an effective but easily navigable approach is demonstrated to modulate the crystallinity of SMAs toward synergistically improved morphologies and molecular orientations of bulk heterojunction enabling highly efficient OSCs.

Nonfullerene‐based small‐molecule organic solar cells with a new record efficiency of 12.08% are achieved by first incorporation of near‐infrared absorbing molecules and by tuning the sequentially evolved crystalline morphology. The improved crystallinity of both donor and acceptor materials facilitates the formation of multilength scale morphologies, which further enhance charge mobility and extraction, and reduce the nongeminate recombination.

Abstract

In this paper, two near‐infrared absorbing molecules are successfully incorporated into nonfullerene‐based small‐molecule organic solar cells (NFSM‐OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP‐TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP‐TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J _sc. These result in a very respectable PCE, which is the highest among all NFSM‐OSCs and all small‐molecule binary solar cells reported so far.

A tandem organic solar cell is fabricated employing subcells with the same donor PBDB‐T and two acceptors F‐M and NNBDT with complementary absorptions. A power conversion efficiency of 14.52% is achieved with a high V _oc of 1.82 V, a notable FF of 74.7%, and a decent J _sc of 10.68 mA cm⁻².

Abstract

The tandem structure is an efficient way to simultaneously tackle absorption and thermalization losses of the single junction solar cells. In this work, a high‐performance tandem organic solar cell (OSC) using two subcells with the same donor poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione))] (PBDB‐T) and two acceptors, F‐M and 2,9‐bis(2‐methylene‐(3(1,1‐dicyanomethylene)benz[f ]indanone))7,12‐dihydro‐(4,4,10,10‐tetrakis(4‐hexylphenyl)‐5,11‐diocthylthieno[3′,2′:4,5]cyclopenta[1,2‐b]thieno[2″,3″:3′,4′]cyclopenta[1′,2′:4,5]thieno[2,3‐f][1]benzothiophene (NNBDT), with complementary absorptions is demonstrated. The two subcells show high V _oc with value of 0.99 V for the front cell and 0.86 V for the rear cell, which is the prerequisite for obtaining high V _oc of their series‐connected tandem device. Although there is much absorption overlap for the subcells, a decent J _sc of the tandem cell is still obtained owing to the complementary absorption of the two acceptors in a wide range. With systematic device optimizations, a best power conversion efficiency of 14.52% is achieved for the tandem device, with a high V _oc of 1.82 V, a notable FF of 74.7%, and a decent J _sc of 10.68 mA cm⁻². This work demonstrates a promising strategy of fabricating high‐efficiency tandem OSCs through elaborate selection of the active layer materials in each subcell and tradeoff of the V _oc and J _sc of the tandem cells.

Two solid additives are proven to improve the molecular packing of acceptors, while devices processed with different additives exhibit different photovoltaic performances due to the different volatilities. The working mechanism and basic design rules of solid additives are revealed, and a feasible method for achieving high‐efficiency polymer solar cells is established.

Abstract

Fine‐tuning of the nanoscale morphologies of the active layers in polymer solar cells (PSCs) through various techniques plays a vital role in improving the photovoltaic performance. However, for emerging nonfullerene (NF) PSCs, the morphology optimization of the active‐layer films empirically follows the methods originally developed in fullerene‐based blends and lacks systematic studies. In this work, two solid additives with different volatilities, SA‐4 and SA‐7, are applied to investigate their influence on the morphologies and photovoltaic performances of NF‐PSCs. Although both solid additives effectively promote the molecular packing of the NF acceptors, due to the higher volatility of SA‐4, the devices processed with SA‐4 exhibit a power conversion efficiency of 13.5%, higher than that of the control devices, and the devices processed with SA‐7 exhibit poor performances. Through a series of detailed morphological analyses, it is found that the volatilization of SA‐4 after thermal annealing is beneficial for the self‐assembly packing of acceptors, while the residuals due to the incomplete volatilization of SA‐7 have a negative effect on the film morphology. The results delineate the feasibility of applying volatilizable solid additives and provide deeper insights into the working mechanism, establishing guidelines for further material design of solid additives.

A facile and eco‐friendly approach is introduced to greatly promote the molecular order of nominally amorphous polymers and thus realize high‐efficiency in sequentially deposited (SD) nonfullerene solar cells. Applying a green solvent, (R)‐(+)‐limonene, enhances the polymer order and yields the best efficiency. Additionally, strong relationships between solvent, interaction parameter, and long period are observed for these new SD devices.

Abstract

Casting of a donor:acceptor bulk‐heterojunction structure from a single ink has been the predominant fabrication method of organic photovoltaics (OPVs). Despite the success of such bulk heterojunctions, the task ofcontrolling the microstructure in a single casting process has been arduous and alternative approaches are desired. To achieve OPVs with a desirable microstructure, a facile and eco‐compatible sequential deposition approach is demonstrated for polymer/small‐molecule pairs. Using a nominally amorphous polymer as the model material, the profound influence of casting solvent is shown on the molecular ordering of the film, and thus the device performance and mesoscale morphology of sequentially deposited OPVs can be tuned. Static and in situ X‐ray scattering indicate that applying (R)‐(+)‐limonene is able to greatly promote the molecular order of weakly crystalline polymers and form the largest domain spacing exclusively, which correlates well with the best efficiency of 12.5% in sequentially deposited devices. The sequentially cast device generally outperforms its control device based on traditional single‐ink bulk‐heterojunction structure. More crucially, a simple polymer:solvent interaction parameter χ is positively correlated with domain spacing in these sequentially deposited devices. These findings shed light on innovative approaches to rationally create environmentally friendly and highly efficient electronics.

3D chiral hybrid organic–inorganic perovskites are both kinetically and thermodynamically stable based on theoretical calculation, and chirality is transferred from chiral cations to the perovskite framework, which is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics.

Abstract

Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics.

Halide perovskites are a promising platform for the construction of nonlinear optical materials in light of their structural diversity, high hyperpolarizability, and bandgap tunability. The current state of the art in purely inorganic and organic–inorganic hybrid halide perovskites as nonlinear optical materials is reviewed and their potential in various nonlinear photonic applications is discussed.

Abstract

Halide perovskites provide an ideal platform for engineering highly promising semiconductor materials for a wide range of applications in optoelectronic devices, such as photovoltaics, light‐emitting diodes, photodetectors, and lasers. More recently, increasing research efforts have been directed toward the nonlinear optical properties of halide perovskites because of their unique chemical and electronic properties, which are of crucial importance for advancing their applications in next‐generation photonic devices. Here, the current state of the art in the field of nonlinear optics (NLO) in halide perovskite materials is reviewed. Halide perovskites are categorized into hybrid organic/inorganic and pure inorganic ones, and their second‐, third‐, and higher‐order NLO properties are summarized. The performance of halide perovskite materials in NLO devices such as upconversion lasers and ultrafast laser modulators is analyzed. Several potential perspectives and research directions of these promising materials for nonlinear optics are presented.

Employing an electron‐deficient‐core‐based fused structure instead of a fused donor unit represents a new strategy to adjust the optoelectronic properties of acceptor–donor–acceptor‐type n‐type organic semiconductors. The electron‐deficient‐core based on benzothiadiazole together with dicyanomethylene derivative realizes a low bandgap, high electron mobility, and suitable energy level simultaneously, affording universal and high performances when blending with different donor polymers.

Abstract

Narrow bandgap n‐type organic semiconductors (n‐OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n‐OS acceptor, Y5, with an electron‐deficient‐core‐based fused structure is designed and synthesized, which exhibits a strong absorption in the 600–900 nm region with an extinction coefficient of 1.24 × 10⁵ cm⁻¹, and an electron mobility of 2.11 × 10⁻⁴ cm² V⁻¹ s⁻¹. By blending Y5 with three types of common medium‐bandgap polymers (J61, PBDB‐T, and TTFQx‐T1) as donors, all devices exhibit high short‐circuit current densities over 20 mA cm⁻². As a result, the power conversion efficiency of the Y5‐based OSCs with J61, TTFQx‐T1, and PBDB‐T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n‐OS acceptor for applications in organic solar cells.

First‐principles calculations are used to investigate the possibilities of spinel compounds AB₂X₄, which combine tetrahedral and octahedral coordination, as alternatives to perovskites and conventional semiconductors for potential photovoltaic applications. The idea of materials design for solar cell absorbers via polyhedral building blocks lies in the revealed complementary properties of octahedral (e.g. perovskite CH₃NH₃PbI₃, CsPbI₃) and tetrahedral coordinated structures (e.g. Si, GaAs, CdTe).

Abstract

Tetrahedral coordination structures, e.g. crystalline Si, GaAs, CdTe, and octahedral coordination structures, e.g. perovskites, represent two classes of successful crystal structures hitherto for solar cell absorbers. Here, via first‐principles calculations and crystal symmetry analysis, the two classes of semiconductors are shown exhibiting complementary properties in terms of bond covalency/ionicity, optical property, defect tolerance, and stability, which are correlated with their respective coordination number. Therefore, a spinel structure is proposed, which combines tetrahedral and octahedral coordination into a single crystal structure, as an alternative to perovskite and conventional semiconductors for potential photovoltaic applications. The case studies of a class of 105 spinel AB₂X₄ systems identify five spinel compounds HgAl₂Se₄, HgIn₂S₄, CdIn₂Se₄, HgSc₂S₄, and HgY₂S₄ as promising solar cell absorbers. In particular, HgAl₂Se₄ has suitable bandgap (1.36 eV by GW0 calculation), small direct–indirect bandgap difference (24 meV), appropriate carrier effective mass (m_e = 0.08 m₀, and m_h = 0.69 m₀), strong optical absorption, and high dynamic stability. This study suggests that crystal systems with mixed tetrahedral and octahedral coordination may open a viable route for emerging solar cell absorbers.

A highly efficient, stable, and ductile nonfullerene ternary organic solar cell by integrating two polymer donors and one acceptor is achieved. The enhanced performance and stability are mainly attributed to the suppressed crystallization of the nonfullerene acceptor by introducing a stiff donor that shows low miscibility with the acceptor and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer.

Abstract

Organic solar cells (OSCs) are one of the most promising cost‐effective options for utilizing solar energy, and, while the field of OSCs has progressed rapidly in device performance in the past few years, the stability of nonfullerene OSCs has received less attention. Developing devices with both high performance and long‐term stability remains challenging, particularly if the material choice is restricted by roll‐to‐roll and benign solvent processing requirements and desirable mechanical durability. Building upon the ink (toluene:FTAZ:IT‐M) that broke the 10% benchmark when blade‐coated in air, a second donor material (PBDB‐T) is introduced to stabilize and enhance performance with power conversion efficiency over 13% while keeping toluene as the solvent. More importantly, the ternary OSCs exhibit excellent thermal stability and storage stability while retaining high ductility. The excellent performance and stability are mainly attributed to the inhibition of the crystallization of nonfullerene small‐molecular acceptors (SMAs) by introducing a stiff donor that also shows low miscibility with the nonfullerene SMA and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer. The study indicates that improved stability and performance can be achieved in a synergistic way without significant embrittlement, which will accelerate the future development and application of nonfullerene OSCs.

Nonfullerene‐based small‐molecule organic solar cells with a new record efficiency of 12.08% are achieved by first incorporation of near‐infrared absorbing molecules and by tuning the sequentially evolved crystalline morphology. The improved crystallinity of both donor and acceptor materials facilitates the formation of multilength scale morphologies, which further enhance charge mobility and extraction, and reduce the nongeminate recombination.

Abstract

In this paper, two near‐infrared absorbing molecules are successfully incorporated into nonfullerene‐based small‐molecule organic solar cells (NFSM‐OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP‐TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP‐TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J _sc. These result in a very respectable PCE, which is the highest among all NFSM‐OSCs and all small‐molecule binary solar cells reported so far.

An effective but simple approach to rationally tune the crystallinity and miscibility of small‐molecular acceptors is reported. With a phenyl introduced at the tail of alkyl side chains, the morphology and molecular orientations of heterojunction are greatly improved. Outstanding efficiencies of 13.23% and 14.04% are detected from the as‐cast and annealed devices, promoted by the fairly high fill factors.

Abstract

Research on fused‐ring small‐molecular‐acceptors (SMAs) has deeply advanced the development of organic solar cells (OSCs). Compared to fruitful studies of ladder‐type cores and end‐caps of SMAs, the exploration of side chains is monotonous. The widely utilized alkyl and aryl side chains usually produce a conflicting association between SMAs' crystallinity and miscibility. Herein, a fresh idea about the modification of side chains is reported to explore the subtle balance between the crystallinity and miscibility. Specifically, a phenyl is introduced to the tail of the alkyl side chain whereby a new acceptor IDIC‐C4Ph is reported. Moderately weakened crystallinity is observed, while maintaining preferred absorption profiles and face‐on orientations. Concurrently, remarkably improved heterojunction morphologies and stacking orientations are detected. PBDB‐T:IDIC‐C4Ph devices exhibit greater efficiency of 11.50% than devices from alky and aryl modified acceptors. Notably, the as‐cast OSCs of PBDB‐TF:IDIC‐C4Ph reveal outstanding FF over 76% with the best efficiency up to 13.23%. The annealed devices reveal further increased efficiency exceeding 14% with the state of the art FF of 78.32%. Overall, an effective but easily navigable approach is demonstrated to modulate the crystallinity of SMAs toward synergistically improved morphologies and molecular orientations of bulk heterojunction enabling highly efficient OSCs.

3D chiral hybrid organic–inorganic perovskites are both kinetically and thermodynamically stable based on theoretical calculation, and chirality is transferred from chiral cations to the perovskite framework, which is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics.

Abstract

Hybrid organic–inorganic perovskites (HOIPs), in particular 3D HOIPs, have demonstrated remarkable properties, including ultralong charge‐carrier diffusion lengths, high dielectric constants, low trap densities, tunable absorption and emission wavelengths, strong spin–orbit coupling, and large Rashba splitting. These superior properties have generated intensive research interest in HOIPs for high‐performance optoelectronics and spintronics. Here, 3D hybrid organic–inorganic perovskites that implant chirality through introducing the chiral methylammonium cation are demonstrated. Based on structural optimization, phonon spectra, formation energy, and ab initio molecular dynamics simulations, it is found that the chirality of the chiral cations can be successfully transferred to the framework of 3D HOIPs, and the resulting 3D chiral HOIPs are both kinetically and thermodynamically stable. Combining chirality with the impressive optical, electrical, and spintronic properties of 3D perovskites, 3D chiral perovskites is of great interest in the fields of piezoelectricity, pyroelectricity, ferroelectricity, topological quantum engineering, circularly polarized optoelectronics, and spintronics.

Employing an electron‐deficient‐core‐based fused structure instead of a fused donor unit represents a new strategy to adjust the optoelectronic properties of acceptor–donor–acceptor‐type n‐type organic semiconductors. The electron‐deficient‐core based on benzothiadiazole together with dicyanomethylene derivative realizes a low bandgap, high electron mobility, and suitable energy level simultaneously, affording universal and high performances when blending with different donor polymers.

Abstract

Narrow bandgap n‐type organic semiconductors (n‐OS) have attracted great attention in recent years as acceptors in organic solar cells (OSCs), due to their easily tuned absorption and electronic energy levels in comparison with fullerene acceptors. Herein, a new n‐OS acceptor, Y5, with an electron‐deficient‐core‐based fused structure is designed and synthesized, which exhibits a strong absorption in the 600–900 nm region with an extinction coefficient of 1.24 × 10⁵ cm⁻¹, and an electron mobility of 2.11 × 10⁻⁴ cm² V⁻¹ s⁻¹. By blending Y5 with three types of common medium‐bandgap polymers (J61, PBDB‐T, and TTFQx‐T1) as donors, all devices exhibit high short‐circuit current densities over 20 mA cm⁻². As a result, the power conversion efficiency of the Y5‐based OSCs with J61, TTFQx‐T1, and PBDB‐T reaches 11.0%, 13.1%, and 14.1%, respectively. This indicates that Y5 is a universal and highly efficient n‐OS acceptor for applications in organic solar cells.

A highly efficient, stable, and ductile nonfullerene ternary organic solar cell by integrating two polymer donors and one acceptor is achieved. The enhanced performance and stability are mainly attributed to the suppressed crystallization of the nonfullerene acceptor by introducing a stiff donor that shows low miscibility with the acceptor and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer.

Abstract

Organic solar cells (OSCs) are one of the most promising cost‐effective options for utilizing solar energy, and, while the field of OSCs has progressed rapidly in device performance in the past few years, the stability of nonfullerene OSCs has received less attention. Developing devices with both high performance and long‐term stability remains challenging, particularly if the material choice is restricted by roll‐to‐roll and benign solvent processing requirements and desirable mechanical durability. Building upon the ink (toluene:FTAZ:IT‐M) that broke the 10% benchmark when blade‐coated in air, a second donor material (PBDB‐T) is introduced to stabilize and enhance performance with power conversion efficiency over 13% while keeping toluene as the solvent. More importantly, the ternary OSCs exhibit excellent thermal stability and storage stability while retaining high ductility. The excellent performance and stability are mainly attributed to the inhibition of the crystallization of nonfullerene small‐molecular acceptors (SMAs) by introducing a stiff donor that also shows low miscibility with the nonfullerene SMA and a slightly higher highest occupied molecular orbital (HOMO) than the host polymer. The study indicates that improved stability and performance can be achieved in a synergistic way without significant embrittlement, which will accelerate the future development and application of nonfullerene OSCs.

An effective but simple approach to rationally tune the crystallinity and miscibility of small‐molecular acceptors is reported. With a phenyl introduced at the tail of alkyl side chains, the morphology and molecular orientations of heterojunction are greatly improved. Outstanding efficiencies of 13.23% and 14.04% are detected from the as‐cast and annealed devices, promoted by the fairly high fill factors.

Abstract

Research on fused‐ring small‐molecular‐acceptors (SMAs) has deeply advanced the development of organic solar cells (OSCs). Compared to fruitful studies of ladder‐type cores and end‐caps of SMAs, the exploration of side chains is monotonous. The widely utilized alkyl and aryl side chains usually produce a conflicting association between SMAs' crystallinity and miscibility. Herein, a fresh idea about the modification of side chains is reported to explore the subtle balance between the crystallinity and miscibility. Specifically, a phenyl is introduced to the tail of the alkyl side chain whereby a new acceptor IDIC‐C4Ph is reported. Moderately weakened crystallinity is observed, while maintaining preferred absorption profiles and face‐on orientations. Concurrently, remarkably improved heterojunction morphologies and stacking orientations are detected. PBDB‐T:IDIC‐C4Ph devices exhibit greater efficiency of 11.50% than devices from alky and aryl modified acceptors. Notably, the as‐cast OSCs of PBDB‐TF:IDIC‐C4Ph reveal outstanding FF over 76% with the best efficiency up to 13.23%. The annealed devices reveal further increased efficiency exceeding 14% with the state of the art FF of 78.32%. Overall, an effective but easily navigable approach is demonstrated to modulate the crystallinity of SMAs toward synergistically improved morphologies and molecular orientations of bulk heterojunction enabling highly efficient OSCs.

Nonfullerene‐based small‐molecule organic solar cells with a new record efficiency of 12.08% are achieved by first incorporation of near‐infrared absorbing molecules and by tuning the sequentially evolved crystalline morphology. The improved crystallinity of both donor and acceptor materials facilitates the formation of multilength scale morphologies, which further enhance charge mobility and extraction, and reduce the nongeminate recombination.

Abstract

In this paper, two near‐infrared absorbing molecules are successfully incorporated into nonfullerene‐based small‐molecule organic solar cells (NFSM‐OSCs) to achieve a very high power conversion efficiency (PCE) of 12.08%. This is achieved by tuning the sequentially evolved crystalline morphology through combined solvent additive and solvent vapor annealing, which mainly work on ZnP‐TBO and 6TIC, respectively. It not only helps improve the crystallinity of the ZnP‐TBO and 6TIC blend, but also forms multilength scale morphology to enhance charge mobility and charge extraction. Moreover, it simultaneously reduces the nongeminate recombination by effective charge delocalization. The resultant device performance shows remarkably enhanced fill factor and J _sc. These result in a very respectable PCE, which is the highest among all NFSM‐OSCs and all small‐molecule binary solar cells reported so far.