Chen Weijie

Herein, four different types of bilayer organic solar cell (OSC) structures using sequential processing (SP) with an additive bilayer are investigated and considerably enhanced device performance is demonstrated. As a result, remarkable power conversion efficiencies of 8.78% and 15.16% for PTB7-Th/PCBM and PM6/Y6 bilayer OSCs, respectively, using the SP with additive bilayer method are achieved.

Despite the research value of bilayer organic solar cells (OSCs) for commercialization in the future, the bulk-heterojunction (BHJ) structure dominates the fabrication of OSCs because of its higher power conversion efficiency (PCE) compared with bilayer OSCs. Herein, four different types of bilayer OSC structures using sequential processing (SP) with an additive bilayer are investigated and considerably enhanced device performance is demonstrated. The performance of our bilayer devices based on a wide bandgap (PBDT-DPPD-TPD; P2) polymer and [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) is improved from 2.88% for the conventional bilayer structure to 6.62%. More importantly, remarkable PCEs of 8.78% and 15.16% for PTB7-Th/PCBM and PM6/Y6 bilayer OSCs, respectively, using the SP with additive bilayer method are achieved and the inhomogeneity issues of the BHJ structure are successfully addressed. Herein, a novel way to overcome the low efficiency of bilayer OSCs is suggested and an unprecedented possibility of renovation, breaking the standardization of OSC research, is presented.

The nanoarchitectonic concept is applied to the design of photoelectrodes built on two types of cluster core building blocks based on {Re₆Sⁱ ₈} and {Re₆Seⁱ ₈} cluster cores. Mixing the two types of building blocks leads to the formation of p–n nanoheterojunctions that enhances the generation of photocurrent, thanks to band bending phenomena.

This study deals with the nanoarchitectonic concept applied to the design of photoelectrodes built on two types of cluster core building blocks, namely, {Re₆Sⁱ ₈} and {Re₆Seⁱ ₈}. The effect of the nature of the metal/ligand on photoinduced conductivity properties is thus investigated through an in-depth photoelectrochemical study and it is rationalized by the establishment of an energy diagram using a set of complementary optical (ultraviolet–vis–near infrared), electrochemical and spectroscopic (X-ray photoelectron spectroscopy) characterization techniques. The optical and electronic properties of {Re₆Qⁱ ₈}-based films (Q = S or Se) are drastically dependent on the composition. The sulfide-based photoelectrodes exhibit ambipolar behavior with an n-type domination whereas the selenide-based photoelectrodes have a p-type semiconducting behavior. Such electronic properties can be exalted by increasing the interactions between the cluster building blocks by heating. The design of mixed {Re₆Qⁱ ₈}-based photoelectrodes combining the two n-{Re₆Sⁱ ₈} and p-{Re₆Seⁱ ₈} cluster core-based building blocks is explored. The physical properties of the heterostructures can be tuned by controlling the {Re₆Sⁱ ₈}:{Re₆Seⁱ ₈} ratio and the interaction between the clusters. The creation of such nanoarchitectonic p–n junctions allows the optimization of the photocurrents generated by increasing the separated charge state lifetime that turns out to be attractive for solar cell applications.

Wide-bandgap perovskite (FA_0.8Cs_0.2Pb(I_0.7Br_0.3)₃ shows significant potential in perovskite-based tandem solar cells. Nevertheless, photoinduced phase segregation is an obstacle that needs to be resolved urgently. It is revealed that the potassium chloride additive can suppress phase segregation optimally by pairing the excess iodide ions around the grain boundaries. Consequently, the efficiency of KCl-modified wide-bandgap devices is improved from 17.18% to 19.34%.

Wide-bandgap perovskites have attracted much attention due to their potential application in perovskite-based tandem solar cells, which can surpass the theoretical efficiency up-limit of single-junction solar cells. However, photoinduced phase segregation remains one of the most intractable impediments that deteriorate the operational stability of wide-bandgap perovskites solar cells. Herein, the effect of a series of alkali halides additives on the photoinduced phase segregation of wide-bandgap perovskites with the composition of FA_0.8Cs_0.2Pb(I_0.7Br_0.3)₃ (FA is formamidinium) is systematically studied. By coupling in situ time-dependent photoluminescence technique, potassium chloride (KCl) is demonstrated to be the best in suppressing the photoinduced phase segregation. The reduced iodine vacancy defects owing to supplemented chloride ions and the coupling of potassium ions with the accumulated iodide ions at the grain boundaries lead to effective suppression phase segregation. As a consequence, the KCl-modified wide-bandgap perovskite solar cells present a champion efficiency of 19.34%, and the devices can maintain 93% of the initial efficiency after light soaking for 500 h with maximum power point tracking under 1 sun equivalent white light-emitting diode illumination, much superior to the reference device without KCl modification only retaining 72% of its initial efficiency.

Herein, dimethyldichlorosilane (DMDCS) is used to passivate the grain boundaries and surfaces of MAPbI₃ perovskite films during its fabricating in air, achieving an excellent power conversion efficiency of 20.69%. The perovskite solar cells with the DMDCS modification retain 80% of the initial efficiency after 1000 h in ambient without encapsulation (air environment at relative humidity of 40%–50%).

As perovskite solar cells (PSCs) are sensitive to moisture, they cannot be prepared in the open air, which increases manufacturing costs. To address this issue, bifunctional dimethyldichlorosilane (DMDCS) is employed as both an additive and capping layer to passivate the grain boundaries and surfaces of MAPbI₃ perovskite films, thus inhibiting water erosion. Accordingly, the preparation of highly efficient PSCs in an air atmosphere is realized. Herein, the passivation mechanism of DMDCS on the perovskite film and the interface is analyzed by investigating photoexcited carrier mobility and ultrafast transient adsorption spectroscopy (TAS). An improvement of charge-carrier diffusion, featuring an enhanced lifetime from 7.62 to 11.22 ps by the precursor doping, is exhibited in the results of TAS. The charge-carrier extraction at the interface is also greatly promoted, with the decreased decay time from 0.29 to 0.16 ns by surface passivation, consistent with the carrier mobility via space charge-limited current. Finally, the modified devices achieve an exceptional efficiency of 20.69%, and demonstrate long-term environmental stability, maintaining more than 80% of the initial efficiency after 1000 h in ambient at a relative humidity of 40% without encapsulation.

A novel green solid additive, 1,8,9-trihydroxyanthracene (TOHA), is utilized to effectively improve both the power conversion efficiency and stability of a highly efficient organic solar cell. The D18-Cl: N3 device achieves a power conversion efficiency of 17.91%, and it maintains 68% of the initial efficiency after 1400 h operation stability.

A novel green solid additive, 1,8,9-Trihydroxyanthracene (TOHA), is demonstrated to effectively improve both efficiency and stability of a highly efficient organic solar cell (OSC), comprising D18-Cl as polymer donor and N3 as small-molecule acceptor. The D18-Cl:N3 device achieves an elevated power conversion efficiency of 17.91%, compared to 17.15% of that processed without TOHA. The enhanced performance is attributed to the addition of TOHA, leading to more refined phase separation and stronger molecular packing in D18-Cl:N3 blend films, and improves the charge generation, exciton dissociation, charge transport, and collection, which contribute to higher photocurrent and fill factor for D18-Cl:N3 OSCs. Meanwhile, TOHA-treated D18-Cl:N3 induces lower ΔE _loss. Remarkably, it can simultaneously enhance the operational stability, with the TOHA-treated OSC maintaining 68% of the initial efficiency after 1400 h operation. Morphology measurement (atomic force microscopy, 2D grazing-incidence wide-angle X-ray scattering, and time-of-flight–secondary-ion mass spectrometry) also illustrates that TOHA improves the stability of the film with smaller Urban energy value of device after aging. TOHA-treated D18-Cl:N3 cell after aging shows smaller reduction on exciton dissociation, charge transport, charge collection, and nonradiative recombination. This work demonstrates the significance of processing condition-controlled additive pathways for the realization of stability, leading to superior OSC devices.

Herein, the intrinsic role of CH₃NH₃Cl doping for efficient enhancement of perovskite solar cells from fine insight by ultrafast charge-transfer dynamics is unraveled. The modifications of molecular-level photophysical processes, which is the origin of the excellent optoelectronic properties of the resulted device, are found out by constructing a diffusion-coupled charge-transport model via ultrafast transient absorption technology.

The addition of CH₃NH₃Cl (MACl) in perovskite precursor has become one of the most effective strategies for enhancing the photovoltaic performance of perovskite solar cells (PSCs). To further determine its relevant intrinsic modification mechanism, a series of PSCs with variant MACl contents are prepared. Apart from the analysis of crystal morphology and defect states, molecular-level photophysical processes related closely to photovoltaic performance are systematically investigated by transient absorption (TA) and time-resolved photoluminescence spectroscopy. Promisingly, by a diffusion-coupled charge-transport model via global fitting of TA spectra, the kinetic of perovskite/SnO₂ heterojunction films is resolved into four distinct photophysical processes. Among the processes, as the MACl concentrations increase, the charge carriers’ bulk diffusion in perovskite and interfacial transfer in perovskite/SnO₂ heterojunction accelerate simultaneously, while the back charge recombination from SnO₂ to perovskite decelerates, which correlates closely with larger grains featuring fewer grain boundaries and defect sites of perovskite induced by MACl doping. The aforementioned modified charge dynamics constitute the origin of the excellent optoelectronic properties in the resultant device, which exhibits an optimal conversion efficiency of 23.6%.

Free charge recombination in disordered organic solar cells proceeds through the formation and decay of charge transfer states. The recombination of free carriers and the non-radiative voltage loss is investigated, to come up with a consistent picture that energetic disorder negatively influences both recombination of free carriers and the voltage loss through the non-radiative decay of the charge transfer state.

Abstract

Reducing non-radiative recombination is key to achieve high fill factors (FFs) in organic solar cells. While it is generally accepted that recombination proceeds via charge transfer (CT) states at the donor:acceptor interface, the underlying principles that dictate the decay kinetics of these CT states are not yet well understood. Here, a study on the effect of energetic disorder is presented. Based on a data set of 10 representative donor:acceptor blends, clear correlations between disorder, the recombination coefficient of free charge carriers, and the non-radiative voltage loss are found. It is suggested that a narrower distribution of CT energies leads to a longer CT decay time and thus reduces non-radiative losses. This leads to a simultaneous improvement of the FF and open circuit voltage and highlights the importance of having materials with low energetic disorder on the way to the commercialisation of organic photovoltaics.

Y-type non-fullerene acceptors with outer branched side chains and inner cyclohexane side chains are designed for polymer solar cells with the power conversion efficiencies of 18.52% and 19.36% achieved in the binary and ternary blend devices, respectively, which are among the highest values for single-junction solar cells at present.

Abstract

Raising the lowest unoccupied molecular orbital (LUMO) energy level of Y-type non-fullerene acceptors can increase the open-circuit voltage (V _oc) and thus the photovoltaic performance of the current top performing polymer solar cells (PSCs). One of the viable routes is demonstrated by the successful Y6 derivative of L8-BO with the branched alkyl chains at the outer side. This will introduce steric hindrance and reduce intermolecular aggregation, thus open up the bandgap and raise the LUMO energy level. To take further advantages of the steric hindrance influence on optoelectronic properties of Y6 derivatives, two Y-type non-fullerene acceptors of BTP-Cy-4F and BTP-Cy-4Cl are designed and synthesized by adopting outer branched side chains and inner cyclohexane side chains. An outstanding V _oc of 0.937 V is achieved in the D18:BTP-Cy-4F binary blend devices along with a power conversion efficiency (PCE) of 18.52%. With the addition of BTP-eC9 to extend the absorption spectral coverage, a remarkable PCE of 19.36% is realized finally in the related ternary blend devices, which is one of the highest values for single-junction PSCs at present. The results illustrate the great potential of cyclohexane side chains in constructing high-performance non-fullerene acceptors and their PSCs.

Deposition of hole transport layers that utilize self-assembled monolayers (SAM-HTLs) has thus far been limited to solution-based methods. Development of alternative scalable deposition methods, such as vacuum-based evaporation techniques, is crucial to improve process flexibility. For the first time, physical vapor deposition (PVD) via thermal evaporation of widely known SAM-HTLs (2PACz, MeO-2PACz, and Me-4PACz) is reported and incorporated into p-i-n perovskite solar cells.

Abstract

Engineering of the interface between perovskite absorber thin films and charge transport layers has fueled the development of perovskite solar cells (PSCs) over the past decade. For p-i-n PSCs, the development and adoption of hole transport layers utilizing self-assembled monolayers (SAM-HTLs) based on carbazole functional groups with phosphonic acid anchoring groups has enabled almost lossless contacts, minimizing interfacial recombination to advance power conversion efficiency in single-junction and tandem solar cells. However, so far these materials have been deposited exclusively via solution-based methods. Here, for the first time, vacuum-based evaporation of the most common carbazole-based SAM-HTLs (2PACz, MeO-2PACz, and Me-4PACz) is reported. X-ray photoelectron spectroscopy and infrared spectroscopy demonstrate no observable chemical differences in the evaporated SAMs compared to solution-processed counterparts. Consequently, the near lossless interfacial properties are either preserved or even slightly improved as demonstrated via photoluminescence measurements and an enhancement in open-circuit voltage. Strikingly, applying evaporated SAM-HTLs to complete PSCs demonstrates comparable performance to their solution-processed counterparts. Furthermore, vacuum deposition is found to improve perovskite wetting and fabrication yield on previously non-ideal materials (namely Me-4PACz) and to display conformal and high-quality coating of micrometer-sized textured surfaces, improving the versatility of these materials without sacrificing their beneficial properties.

Publication date: March 2023

Source: Journal of Energy Chemistry, Volume 78

Author(s): Guibin Shen, Hongye Dong, Fan Yang, Xin Ren Ng, Xin Li, Fen Lin, Cheng Mu

Publication date: April 2023

Source: Journal of Energy Chemistry, Volume 79

Author(s): Dongyang Li, Yulan Huang, Zhiwei Ren, Abbas Amini, Aleksandra B. Djurišić, Chun Cheng, Gang Li

Straying from commonly investigated two- and four-terminal tandem approaches, an alternative monolithically integrated three-terminal perovskite/silicon heterojunction device architecture with a combined efficiency of 24.9% is presented where the additional terminal functions as a current regulator. Thus, current matching is not necessary, and these devices are more stable against spectral variations, which are tested both by simulations and experimentally.

Research on perovskite/silicon tandem solar cells is chiefly focused on devices in either two- or four-terminal configurations (2T and 4T, respectively). Straying from these commonly investigated approaches, an alternative monolithically integrated device architecture using three terminals (3T) by combining a semi-transparent perovskite top cell with a silicon heterojunction bottom cell featuring interdigitated rear contacts is presented. In the presence of a p/n recombination junction between subcells, a quasi-2T configuration is obtained where the additional terminal functions as a current regulator. Thus, in contrast to 2T tandems, current matching between subcells is not necessary. Therefore, these devices are more stable against spectral variations, especially their voltages at maximum power point, as surplus current can be either injected into or extracted from the additional terminal. This is tested both by simulations and for the first time experimentally. Interestingly, the highest power conversion efficiency is not achieved by current matching but by maximizing current generation in the top cell. An experimental realization of a 3T tandem with p/n recombination junction and a power conversion efficiency of 24.9% is presented, thus confirming the general viability of the concept.

A new Cu(II)porphyrin-based acceptor (A)–π–donor–π–A, denoted as VC11, proves to be an excellent third component in ternary organic solar cells with PBDB-T and Y6 affording a power conversion efficiency as high as 15.25% owing to the additional charge separation offered by a cascaded energy-level alignment and a fast charge transfer, due the ambipolarity of VC11.

Ternary architecture is a promising strategy to achieve high efficiency in organic solar cells. The alignment of third-component frontier orbitals with those of donor and acceptor (D and A) is of essential importance. Herein, a new molecule VC11, consisting of a Cu(II)–porphyrin core linked to dicyanovinylene terminal acceptor units through (E)-1,2-di(thiophen-2-yl) ethene bridges, is described. The highest occupied molecular orbital and lowest unoccupied molecular orbital values of VC11 are −5.52 and −3.74 eV, respectively, lying between the corresponding values of PBDB-T donor and Y6 acceptor, compounds used in the construction of the studied devices. The measured electron and hole mobilities reveal similar values, in the order of 10⁻⁴ cm² Vs⁻¹, indicating the ambipolarity of VC11, that can be used as donor or acceptor. The organic solar cells (OSCs) based on PBDB-T:VC11, VC11:Y6, and PBDB-T:Y6 show power conversion efficiencies (PCEs) of 10.84%, 7.89%, and 11.98%, respectively. VC11 is utilized along with PBDB-T and Y6 to form a ternary active layer for assembling bulk heterojunction OSCs affording a remarkable PCE of 15.25%, significantly higher than those obtained for the corresponding binary devices. This enhancement of PCE originates from the additional charge separation offered by a cascaded energy-level alignment and a fast charge transfer, due the ambipolarity of VC11.

Herein, an anion-engineered additive strategy is reported to modify the crystallization process of perovskite films on industrially feasible double-side textured silicon, which enables conformal deposition with improved film crystallinity and reduced trap density. This allows the fabrication of perovskite/silicon tandem solar cells with efficiencies of 28.9% (certified efficiency of 27.9%) and 25.1% for areas of 1 and 16 cm², respectively.

Abstract

Monolithic perovskite/silicon tandem solar cells promise power-conversion efficiencies (PCEs) exceeding the Shockley-Queisser limit of single-junction solar cells. The conformal deposition of perovskites on industrially feasible textured silicon solar cells allows for both lowered manufacturing costs and a higher matched photocurrent density, compared to state-of-the-art tandems using front-side flat or mildly textured silicon. However, the inferior crystal quality of perovskite films grown on fully-textured silicon compromises the photovoltaic performance. Here, an anion-engineered additive strategy is developed to control the crystallization process of wide-bandgap perovskite films, which enables improved film crystallinity, reduced trap density, and conformal deposition on industrially textured silicon. This strategy allows the fabrication of 28.6%-efficient perovskite/silicon heterojunction tandem solar cells (certified 27.9%, 1 cm²). This approach is compatible with the scalable fabrication of tandems on industrially textured silicon, demonstrating an efficiency of 25.1% for an aperture area of 16 cm². The anion-engineered additive significantly improves the operating stability of wide-bandgap perovskite solar cells, and the encapsulated tandem solar cells retain over 80% of their initial performance following 2000 h of operation under full 1-sun illumination in ambient conditions.

Nature Communications, Published online: 04 January 2023; doi:10.1038/s41467-022-35702-7

The study introduces an amorphous F-TiO_x caulked crystalline SnO₂ composite ETL. The F-TiO_x provides more electron transport channels, passivates oxygen vacancies, and fine-tunes the energy level arrangement, thus enhancing the electron mobility of ETL and reducing the charge transport losses. The composite ETL-based f-PSCs achieve a high PCE of 22.70%, together with enhanced operational stability and mechanical reliability.

Abstract

Flexible perovskite solar cells (f-PSCs) show great promise in portable-power applications (e.g., chargers, drones) and low-cost, scalable productions (e.g., roll-to-roll). However, in conventional n–i–p architecture f-PSCs, the low-temperature processed metal oxide electron transport layers (ETLs) usually suffer from high resistance and severe defects that limit the power conversion efficiency (PCE) improvement of f-PSCs. Besides the enhancement in the mobility of metal oxide and passivation for perovskite/ETL interfacial defects reported in previous literature, herein, the electron transport loss between the metal oxide nanocrystallines within the ETL is studied by introducing an amorphous F-doped TiO_x (F-TiO_x) caulked crystalline SnO₂ composite ETL. The F-TiO_x in this novel composite ETL acts as an interstitial medium between adjacent SnO₂ nanocrystallines, which can provide more electron transport channels, effectively passivate oxygen vacancies, and optimize the energy level arrangement, thus significantly enhancing the electron mobility of ETL and reducing the charge transport losses. The composite ETL-based f-PSCs achieve a high PCE of 22.70% and good operational stability. Furthermore, a moderate roughness of the composite ETL endows f-PSCs with superior mechanical reliability by virtue of a strong coupling at the ETL/perovskite interface, by which the f-PSCs can maintain 82.11% of their initial PCE after 4000 bending cycles.

The influence of two isomeric A′-site ligands, linear-shaped n-butylammonium (n-BA⁺) and branched iso-butylammonium (iso-BA⁺), on 2D perovskites is studied from precursor to device. With the aid of dynamic light scattering, in situ grazing-incidence wide-angle X-ray scattering, and density functional theory calculations, the crucial role of organic A′-site ligand structure in the crystal growth of 2D perovskites is unveiled.

Abstract

Organic A′-site ligand structure plays a crucial role in the crystal growth of 2D perovskites, but the underlying mechanism has not been adequately understood. This problem is tackled by studying the influence of two isomeric A′-site ligands, linear-shaped n-butylammonium (n-BA⁺) and branched iso-butylammonium (iso-BA⁺), on 2D perovskites from precursor to device, with a combination of in situ grazing-incidence wide-angle X-ray scattering and density functional theory. It is found that branched iso-BA⁺, due to the lower aggregation enthalpies, tends to form large-size clusters in the precursor solution, which can act as pre-nucleation sites to expedite the crystallization of vertically oriented 2D perovskites. Furthermore, iso-BA⁺ is less likely to be incorporated into the MAPbI₃ lattice than n-BA⁺, suppressing the formation of unwanted multi-oriented perovskites. These findings well explain the better device performance of 2D perovskite solar cells based on iso-BA⁺ and elucidate the fundamental mechanism of ligand structural impact on 2D perovskite crystallization.

Here, a unique and effective hybrid side chain strategy is adopted for synthesizing symmetric/asymmetric small molecular acceptors and enables organic photovoltaic to exhibit a high efficiency of 19.1%. It endows the acceptors with planar skeleton and compact 3D network packing, contributing to optimal donor/acceptor interfacial energetics and accelerated exciton dissociation.

Abstract

Hybrid cycloalkyl-alkyl side chains are considered a unique composite side-chain system for the construction of novel organic semiconductor materials. However, there is a lack of fundamental understanding of the variations in the single-crystal structures as well as the optoelectronic and energetic properties generated by the introduction of hybrid side chains in electron acceptors. Herein, symmetric/asymmetric acceptors (Y-C10ch and A-C10ch) bearing bilateral and unilateral 10-cyclohexyldecyl are designed, synthesized, and compared with the symmetric acceptor 2,2′-((2Z,2′Z)-((12,13-bis(2-butyloctyl)-3,9 bis(ethylhexyl)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″′:4′,5′]thieno[2′,3′:4,5] pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10- diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (L8-BO). The stepwise introduction of 10-cyclohexyldecyl side chains decreases the optical bandgap, deepens the energy level, and enables the acceptor molecules to pack closely in a regular manner. Crystallographic analysis demonstrates that the 10-cyclohexyldecyl chain endows the acceptor with a more planar skeleton and enforces more compact 3D network packing, resulting in an active layer with higher domain purity. Moreover, the 10-cyclohexyldecyl chain affects the donor/acceptor interfacial energetics and accelerates exciton dissociation, enabling a power conversion efficiency (PCE) of >18% in the 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2″,3″′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile (Y6) (PM6):A-C10ch-based organic solar cells (OSCs). Importantly, the incorporation of Y-C10ch as the third component of the PM6:L8-BO blend results in a higher PCE of 19.1%. The superior molecular packing behavior of the 10-cyclohexyldecyl side chain is highlighted here for the fabrication of high-performance OSCs.

Two isomeric A-D₁A′D₂-A type double asymmetric selenophene-based small molecule acceptors (SMAs) were synthesized by a n-nonyl/undecyl regioisomeric strategy to optimize single-crystal packing, improve film morphology, and boost device performance. PM6 : AYT9Se11-Cl achieved a superior PCE of 18.12 % compared to PM6 : AYT11Se9-Cl.

Abstract

Side-chain tailoring is a promising method to optimize the performance of organic solar cells (OSCs). However, asymmetric alkyl chain-based small molecular acceptors (SMAs) are still difficult to afford. Herein, we adopted a novel asymmetric n-nonyl/undecyl substitution strategy and synthesized two A-D₁A′D₂-A double asymmetric isomeric SMAs with asymmetric selenophene-based central core for OSCs. Crystallographic analysis indicates that AYT9Se11-Cl forms a more compact and order intermolecular packing compared to AYT11Se9-Cl, which contributed to higher electron mobility in neat AYT9Se11-Cl film. Moreover, the PM6 : AYT9Se11-Cl blend film shows a better morphology with appropriate phase separation and distinct face-on orientation than PM6 : AYT11Se9-Cl. The OSCs with PM6 : AYT9Se11-Cl obtain a superior PCE of 18.12 % compared to PM6 : AYT11Se9-Cl (17.52 %), which is the best efficiency for the selenium-incorporated SMAs in binary BHJ OSCs. Our findings elucidate that the promising double asymmetric strategy with isomeric alkyl chains precisely modulates the crystal packing and enhances the photovoltaic efficiency of selenophene-incorporated SMAs.

Publication date: February 2023

Source: Journal of Energy Chemistry, Volume 77

Author(s): Tai Wu, Rongjun Zhao, Donglin Jia, Linqin Wang, Xiaoliang Zhang, Licheng Sun, Yong Hua