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A series of wide bandgap terpolymers are designed and synthesized, which exhibit low energetic disorders. Based on the terpolymers, outstanding PCEs of over 31% (1000 lux) for an indoor OPV cell and over 18.2% (one-sun) for an OPV cell are achieved.

By designing new terpolymers, we tuned the molecular orientation to obtain an ordered morphology with suppressed energetic disorder. Thus, we boost the PCE of all-PSCs to over 18%.

Large voltage losses are the main obstacle for achieving high efficiency in organic solar cells (OSCs). Here we construct ternary OSCs by introducing an asymmetric small molecule acceptor AITC into PBDB-TCl: BTP-eC9 system and demonstrate the effectiveness in simultaneously decreasing energy disorder and non-radiative voltage losses. It is found that the introduction of AITC can modify domain size and increase degree of crystallinity, which enhances the open circuit voltage and power conversion efficiency (19.1%, certified as 18.9%). Inspiringly, the constructed tandem OSCs based on PBDB-TCl: AITC: BTP-eC9 ternary active layer output a recorded efficiency of 20.6% (certified as 20.3%), which is the highest value in OSCs field till now. This work demonstrates that decreasing the voltage losses by ternary strategy and constructing of tandem architecture are effective approaches towards improving the photovoltaic performance.

An asymmetric wide-bandgap acceptor, namely AITC, is synthesized. The large dipole moment of AITC reinforces the molecular packing in ternary blends. Single-junction and tandem OSCs yielded a remarkable PCE of 18.8% and 19.4%, respectively.

Summary Reducing non-radiative charge recombination is of critical importance to achieving high-performance organic photovoltaic (OPV) cells. The correlation between the exciton behaviors and non-radiative charge recombination is rarely studied. In this work, we achieved an increase in the exciton diffusion length (LD) in the acceptor phase via introducing HDO-4Cl to the PBDB-TF:eC9-based system. Compared with the eC9-based film, the exciton LD in the HDO-4Cl:eC9-based film is increased from 12.2 to 16.3 nm. The enlarged exciton LD can obviously decrease the non-radiative charge recombination and increase the efficiency of photon utilization in the PBDB-TF:eC9-based OPV cell. Finally, we not only obtained an outstanding power conversion efficiency (PCE) of 18.86% but also demonstrated the correlations between the non-radiative energy loss and exciton behaviors. The results show that regulating the exciton behaviors is an effective way to reduce the non-radiative energy loss and realize high-efficiency OPV cells.

The power conversion efficiencies (PCEs) of organic solar cells (OSCs) have reached 18% recently, which have already met the demand of practical application. However, these outstanding results were generally achieved with donor-acceptor (D-A) type copolymer donors, which can hardly fulfill the low-cost large-scale production due to their complicated synthesis processes. Therefore, developing polymer donors with simple chemical structures is urgent for realizing low-cost OSCs. Polythiophene (PT) derivatives are currently regarded as promising candidates for such kind of donor materials, which has been illustrated in many works. In this work, two new alkylthio substituted PT derivatives, P301 and P302, were synthesized and tested as donors in the OSCs using Y5 as the acceptor. In comparison, the introduction of fluorine atoms on the backbone of P302 can not only downshift the energy levels, but also greatly improve the phase separation morphologies of the active layers, which is ascribed to the enhanced aggregation effect and the reduced miscibility with the non-fullerene acceptor. As a result, the P302:Y5-based OSC exhibits a significantly improved PCE of 9.65% than that of P301:Y5-based one, indicating the important role of fluorination in the construction of efficient PT derivative donors.

Summary At present, PEDOT:PSS and MoO3 are the most widely used hole transport layer (HTL) in organic solar cells (OSCs); however, some drawbacks still limit their practical use. In this study, we developed a facile method to enhance the conductivity of a polyoxometalate-based inorganic cluster (PIC) without sacrificing its high work function nature. An inorganic cluster HPMO:Sn with excellent hole collection ability was prepared and used as an HTL in an OSC achieving a power conversion efficiency (PCE) of 17.3%. To the best of our knowledge, the photovoltaic performances are among the best devices reported in the field. Moreover, HPMO:Sn possesses the merits of a definite and stable chemical structure and is low cost, and HPMO:Sn can be easily prepared without any post-treatment. Besides, we prove that the HPMO:Sn HTL is very compatible with blade coating, i.e., an OSC of 1.0 cm2 was fabricated using a blade-coated HPMO:Sn film to attain an efficiency of 15.1%.

Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated. Favorable vertical phase distribution with donors (acceptors) accumulated (depleted) at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6. In addition, N2200 is gradiently distributed in the vertical direction in the ternary blend film. Various measurements were carried out to study the effects of N2200 on the binary systems. It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films, which is beneficial for the charge transport and collection. All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells (OSCs), and power conversion efficiencies (PCEs) of 12.5% and 16.42% were obtained for the ternary OSCs, respectively. This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.

For all small-molecule-based organic solar cells (SM-OSCs), it is very challenging to obtain a nanoscale bicontinuous network structure in the active layers, so their power conversion efficiencies (PCEs) still lag behind those of the polymer-based OSCs. In this work, highly efficient SM-OSCs based on a ternary bulk heterojunction (BHJ) layer of B1:BO-2Cl:BO-4Cl were constructed. Ternary cells with the three different BO-2Cl:BO-4Cl weight ratios exhibit higher PCEs than those of B1:BO-2Cl- and B1:BO-4Cl-based binary cells. The results obtained from the transient absorption, time-resolved photoluminescence spectroscopy and device physics analysis reveal that the ternary cell with the optimal composition (B1:BO-2Cl:BO-4Cl = 1 : 0.5 : 0.5 in weight ratio) exhibits faster charge transfer processes, suppressed geminate and non-geminate charge recombination, lower energetic disorder, and higher and more symmetric carrier mobilities than the two binary cells. The transmission electron microscopy measurement results reveal that the nanoscale bicontinuous interpenetrating network with a hierarchical branched structure can be fully evolved in the BHJ layer with the optimal ternary composition. As a result, the optimal ternary cell exhibits a PCE of 17.0% (certified to be 16.9%) and a fill factor of 0.78, which are the highest values obtained for SM-OSCs.

The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was used to monitor the charge dynamics within the bulk heterojunction. It is striking to find that there is still charge transfer and charge generation when the energy offset reached -0.10 eV (ultraviolet photoelectron spectroscopy data). This work not only indicates the feasibility of the free carrier generation and the following charge separation under the condition of a negative offset but also elucidates the relationship between the charge transfer and the energy offset in the case of polymer chlorination.

The innovation of photoactive layer materials is crucial for improving the power conversion efficiency (PCE) of polymer solar cells (PSCs). Herein, we report two polymer donors (PBTN-o and PBTN-p), which only differ in alkyl chains substituted at sites (6,7- or 5,8-) of the naphtho[2,3-c]thiophene-4,9-dione (NTD) unit. The single crystals of both NTD monomers demonstrate that NTD with alkyl chains at the 6,7-sites has a planar NTD skeleton, and surprisingly, NTD with alkyl chains at the 5,8-sites produces a bent NTD skeleton. The bent NTD-based polymer (PBTN-p) exhibits a more twisted conjugated backbone than PBTN-o. Our comparative studies show that PBTN-p possesses suitable aggregation properties that can optimize the photoactive layer morphology in NF PSCs. In PSCs, the optimal PBTN-o:BO-4Cl-based device shows a PCE of 11.85% with a VOC of 0.84 V, JSC of 22.41 mA cm−2, and FF of 0.63. In contrast, the optimal PBTN-p:BO-4Cl-based device exhibits a better PCE of 14.10% with the same VOC of 0.84 V, and an enhanced JSC of 24.67 mA cm−2 and FF of 0.68. This work provides a new insight into BHJ morphology optimization by side chain induced polymer main chain twisting in PSCs.

The advantage of low cost makes P3HT one of the most attractive electron donors for photovoltaic applications, but the power conversion efficiency (PCE) of the P3HT-based organic solar cells (OSCs) remains low (7–8%). Herein, to modulate the phase separation morphology so as to enhance the PCE in P3HT-based OSCs, a new NFA, namely ZY-4Cl, is designed and synthesized by modifying the cyano-substituted end groups in BTP-4Cl. The P3HT:ZY-4Cl based OSC exhibits a significantly improved PCE of ∼9.5%, which is a new record for the P3HT-based OSCs. Furthermore, two model compounds, TT-CN and TT-O, are synthesized to simulate the end groups of BTP-4Cl and ZY-4Cl, respectively. The calculated Flory-Huggins interaction parameter, the DSC and the AFM results clearly indicate that the cyano-substituted compound TT-CN shows much stronger miscibility with P3HT compared to TT-O, the one without cyano groups. This molecular design strategy is also verified in the other two representative NFAs. Therefore, this work not only reports an NFA with a high PCE for P3HT-based OSCs, but also suggests guidance for the molecular design of NFAs from the aspect of morphology control.

The development of organic photoactive materials, especially the newly emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells. More crucially, as the optimal NFA has a suitable solubility and thus a desirable morphology, the high efficiencies of spin-coated devices can be maintained when using scalable blade-coating processing technology. Our results suggest that optimization of the chemical structures of the OPV materials can improve device performance. This has great significance in larger-area production technologies that provide important scientific insights for the commercialization of OPV cells.

The performance degradation of organic photovoltaics is one of the main limitations to their commercialization, especially an initial, rapid degradation-period, termed as a burn-in loss. Herein, we demonstrate that burn-in loss is caused by the presence of thermodynamically unstable mixed-amorphous phase in the active layer. By using a combination of grazing incidence small angle X-ray scattering and photophysical process experiments, we observe that [6,6]-Phenyl C61 butyric acid methyl ester (PC61BM) molecules rapidly move from the finely-mixed amorphous regimes into crystalline or ordered regimes under accelerated conditions (ISOS-D-2 protocol), resulting in a fast short circuit current (Jsc) burn-in loss. Following an ultraviolet radiation (UV) light processing to control amorphous phase, the kinetics of thermally induced PC61BM crystallization can be slowed down due to the formation of the photo-induced PC61BM dimers in the active layer leading to a smaller burn-in loss. In the case of UV irradiated films, even if the molecules migrated out of amorphous phase, the PC61BM-rich phase becomes loose, rather than the compact and sphere-shaped aggregation, which has been observed in pristine films. These analyses reveal the evolution of thermodynamically unstable amorphous phases eventually leading to a decline power conversion efficiency within a short period of time. The results provide a further design basis of organic photovoltaic materials with good thermal stability and high efficient simultaneously.

The composition ratio of donor and acceptor materials in organic bulk heterojunction (BHJ) is one of the key parameters to govern the performance in organic solar cells (OSCs). Therefore, high-performance non-fullerene organic bulk heterojunction consisting of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene))-co-(1,3-di(5-thiophene-2-yl)–5,7-bis(2-ethylhexyl) benzo[1,2-c:4,5-c′]dithiophene-4,8-dione)] (PBDB-T) and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))–5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (ITIC) are used to investigate the correlation among various donor: acceptor (D:A) ratios, photophysical properties and photovoltaic performance. Interestingly, the function of short-circuit current (Jsc) and D:A ratios demonstrates an axisymmetric trend. When the blending ratio of D:A deviates from the optimal ratio, the symmetrically decreased Jsc is derived from a reduction in the D:A interface or amorphous region. Research on the steady-state photoluminescence (PL), the time-resolved fluorescence spectroscopy measurements, atomic force microscopic (AFM) and grazing-incidence small angle X-rays scattering (GIWAXS) indicates no significant variation in energy loss in the process of changing D:A ratios in BHJs. With high donor or acceptor content, the domain size improves significantly, but the distance of π-π stacking corresponding to molecular packing has not changed significantly, and the bi-continuous percolation pathways were not obviously influenced.

Recombination energy loss is the main impediment on improving the power conversion efficiency of organic solar cells (OSCs). The pernicious effect is usually induced by two dynamics, that is, the g...

Nonradiative recombination loss (qΔVocnonrad), as a large component of energy loss (Eloss), has become an important factor that limits the power conversion efficiency (PCE) of organic solar cells (...

The donor:acceptor heterojunction has proved as the most successful approach to split strongly bound excitons in organic solar cells (OSCs). Establishing an ideal architecture with selective carrier transport and suppressed recombination is of great importance to improve the photovoltaic efficiency while remains a challenge. Herein, via tailoring a hybrid planar/bulk structure, highly efficient OSCs with reduced energy losses (Eloss s) are fabricated. A p-type benzodithiophene-thiophene alternating polymer and an n-type naphthalene imide are inserted on both sides of a mixed donor:acceptor active layer to construct the hybrid heterojunction, respectively. The tailored structure with the donor near the anode and the acceptor near the cathode is beneficial for obtaining enhanced charge transport, extraction, and suppressed charge recombination. As a result, the photovoltaic characterizations suggest a reduced nonradiative Eloss by 25 meV, and the best OSC records a high efficiency of 18.5% (certified as 18.2%). This study highlights that precisely regulating the structure of donor:acceptor heterojunction has the potential to further improve the efficiencies of OSCs.

The development of polymerized small-molecule acceptors has boosted the power conversion efficiencies (PCEs) of all-polymer organic photovoltaic (OPV) cells to 17%. However, the polymer donors suitable for all-polymer OPV cells are still lacking, restricting the further improvement of their PCEs. Herein, a new polymer donor named PQM-Cl is designed and its photovoltaic performance is explored. The negative electrostatic potential and low average local ionization energy distribution of the PQM-Cl surface enable efficient charge generation and transfer process. When blending with a well-used polymer acceptor, PY-IT, the PQM-Cl-based devices deliver an impressive PCE of 18.0% with a superior fill factor of 80.7%, both of which are the highest values for all-polymer OPV cells. The relevant measurements demonstrate that PQM-Cl-based films possess excellent mechanical and flexible properties. As such, PQM-Cl-based flexible photovoltaic cells are fabricated and an excellent PCE of 16.5% with high mechanical stability is displayed. These results demonstrate that PQM-Cl is a potential candidate for all-polymer OPV cells and provide insights into the design of polymer donors for high-efficient all-polymer OPV cells.

Developing photovoltaic materials with simple chemical structures and easy synthesis still remains a major challenge in the industrialization process of organic solar cells (OSCs). Herein, an ester substituted poly(thiophene vinylene) derivative, PTVT-T, was designed and synthesized in very few steps by adopting commercially available raw materials. The ester groups on the thiophene units enable PTVT-T to have a planar and stable conformation. Moreover, PTVT-T presents a wide absorption band and strong aggregation effect in solution, which are the key characteristics needed to realize high performance in non-fullerene-acceptor (NFA)-based OSCs. We then prepared OSCs by blending PTVT-T with three representative fullerene- and NF-based acceptors, PC71BM, IT-4F and BTP-eC9. It was found that PTVT-T can work well with all the acceptors, showing great potential to match new emerging NFAs. Particularly, a remarkable power conversion efficiency of 16.20% is achieved in a PTVT-T:BTP-eC9-based device, which is the highest value among the counterparts based on PTV derivatives. This work demonstrates that PTVT-T shows great potential for the future commercialization of OSCs.

This study examines the correlation between the structure of four perylenediimide (PDI) derivatives and their optoelectronic behaviors. Three of them with one, two or four PDI moieties conjugated peripherally to porphyrin core by phenylene linker, denoted as nPDI-ZnP (n = 1,2,4), are investigated as acceptors on the charge transport property and device performance in non-fullerene (NF) bulk-heterojunction (BHJ) organic photovoltaic cells with a commercial polymer PTB7-Th as the donor material. Besides, the parent PDI molecule is studied as a control. Detailed charge carrier transport analysis is carried out on these PTB7-Th:Acceptor BHJs. Among all acceptor molecules, PTB7-Th:4PDI-ZnP film possesses the most desirable transport properties among the NF BHJs, and the best device performance with a power conversion efficiency (PCE) of 8.35%. To quantify the transport behaviors, the charge imbalance factor Δ is introduced to describe the global electron and hole balance in different electric fields. We discover that PTB7-Th:4PDI-ZnP has the least Δ and thereby gives rise to a BHJ cells with the highest fill factor and PCE.

To address the intrinsic issue of conventional porphyrin derivatives with a deficient absorption between Soret and Q bands, we designed and synthesized two porphyrin molecules (BDTP-1 and BDTP-2) bearing a meso-alkyl substituted porphyrin core, benzodithiohene (BDT) ethynylene π-bridge and end-capping ethylrhodanine derivatives. Apart from the characteristic Soret and Q bands of porphyrin macrocycle, an extra peak (521 nm for BDTP-1 and 536 nm for BDTP-2) was derived from the BDT units. Using the porphyrin small molecules as electron donors and PC71BM as an electron acceptor, the devices show broad spectral photocurrent generation with a significant contribution from greenlight-harvesting (490–550 nm), resulting in high performances with PCEs up to 7.97%.

Hybrid organic–inorganic metal halide perovskite solar cells (PSCs) have been regarded as a low-cost, high-efficiency photovoltaic technology; however, the device performance seriously depends on interfacial properties between each contact layer. The interface plays an important role in PSCs as it induces defects, trap states, charge recombination sites etc., which are detrimental to the device performance and stability. Herein, a post-treatment of self-assembling large cations of tert-butylammonium (tBA) on the surface of the perovskite layer is demonstrated as an effective strategy to passivate interface and grain boundary defects and thus improve device performance and stability. In particular, a normal hysteresis is turned into an inverted hysteresis by increasing the amount of tert-butylammonium iodide (tBAI), which can be ascribed to modified interface states. An impressive power conversion efficiency (PCE) over 20% with a significantly suppressed hysteresis is achieved via the careful control of post-treatment conditions, which shows great promise for commercialization in the future.

Ternary solar cells have been proven to be an effective way to increase the power conversion efficiency (PCE) of organic solar cells (OSCs). Up to now, research effort has mostly focused on fullerene derivatives and acceptor–donor–acceptor (A–D–A) type non-fullerene acceptor-based ternary solar cells, while perylene diimide (PDI)-based ternary devices have been rarely studied. In this contribution, we introduced a new type of ternary solar cell based on a PDI-based small-molecule acceptor (PBI-Por) and a polymer donor (PTB7-Th) with a third PDI-based polymer acceptor (PDI-V). The introduction of PDI-V into the ternary blends not only broadens the absorption of blend films but also increases the electron mobilities. As a result, a high efficiency of 9.43% was obtained for the ternary OSC, which is 20% higher than that of the binary OSC. Detailed studies indicate that PDI-V showed good compatibility with PBI-Por in the blend films, which demonstrates a promising way to fabricate high-performance PDI-based OSCs.

Erbium (III) tris(8-hydroxyquinoline) ErQ complex is emerging as a class of novel luminescent material for interfacial engineering to improve the performance of organic solar cells (OSCs). In the present work, ErQ doped ZnO solution has successfully been prepared by the sol-gel route at room temperature as an electron transport layer for high efficient OSCs. The modified ErQ:ZnO films can yield not only higher electron mobility, good surface quality by the passivation of ZnO defects, but also slightly higher work-function and thereby shortening in the leakage current, which subsequently enhanced power conversion efficiency (PCE). As a result, the remarkable PCE increasing from 3.62% to 4.26% for poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) and from 6.84% to 7.95% for polymer thieno [3,4-b] thiophene/benzodithiophene: [6,6] phenyl-C71-butyric acid methyl ester (PTB7:PCB71M) devices could be achieved upon an incorporating ErQ:ZnO interfacial layer.

Among all tandem photovoltaic (PV) techniques, the perovskite/Si tandem is of particular interest as it capitalizes the mature silicon industry with decades of experience. Photo-current matching between two sub-cells is a prerequisite to achieve high efficiency in monolithic tandem cells. Here we report a low-temperature solution process for efficient perovskite/Si tandem solar cell. A highly-efficient perovskite/Si monolithic tandem cell is constructed by adjusting the electrical and optical properties of electron transport layer, and optimizing the bandgap and the optical density of perovskite absorber. With the optimized condition, the tandem cell with 1.69 eV bandgap of the perovskite absorber delivers a power conversion efficiency (PCE) of 22.22%. The steady state efficiency output at 1.42 V could reach over 20.6% over 200 s illumination. In addition, the stability of perovskite/Si two-terminal tandem devices is promising, which retains more than 85% of its original efficiency after 500 h stability test.

The crystallinity of non-fullerene acceptors as the third component has an important role on nanomorphology optimization and charge transfer dynamics of ternary organic solar cells (OSCs). Herein, efficient ternary OSCs were fabricated by incorporating two typical non-fullerene acceptors with different crystallinity, (Z)-5-{[5-(15-{5-[(Z)-(3-Ethyl-4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-8-thia-7.9-diazabicyclo [4.3.0] nona-1 (9),2,4,6-tetraen-2-yl}-9,9,18,18-tetrakis (2-ethylhexyl)-5.14-dithiapentacyclo [10.6.0.03,10.04,8.013,17]octadeca-1(12),2,4(8),6,10,13 (17),15-heptaen-6-yl)-8-thia-7.9-diazabicyclo [4.3.0]nona-1 (9),2,4,6-tetraen-2-yl]methylidene}-3-ethyl-2-thioxo-1,3-thiazolidin-4-one (EH-IDTBR) or (5Z, 5′Z)-5,5'-((7,7'-(4,4,9,9-tetraoctyl-4,9-dihydro-s-indaceno [1,2-b:5,6-b']dithiophene-2,7-diyl)bis (benzo [c][1,2,5]thiadiazole7,4diyl)) bis(methanylylidene))bis (3-ethyl-2-thioxothiazolidin-4-one) (O-IDTBR), into the host donor/acceptor active layers comprising of poly (3-hexythiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C71-butyric acid methylester (PC71BM). As a result, the 21.5% and 22.7% increase of the power conversion efficiency (PCE) for the two ternary systems were achieved, respectively, which was attributed to the enhanced light harvesting capability, optimized bulk-heterojunction morphology and the formation of cascade energy level alignments that could introduce an additional pathway for efficient charge transfer. Although both the short-circuit current density (Jsc) and fill factor (FF) values were increased significantly by regulating the weight ratios of non-fullerene acceptors of two ternary systems, the O-IDTBR-based ternary OSCs showed the higher Jsc while P3HT:EH-IDTBR:PC71BM system exhibited the higher FF values. The main difference of improved photovoltaic performance in the two ternary systems could be associated with the different blend morphology and charge carrier mobilities. In addition, nanomorphology studies suggested that lamellar stacking coherence lengths of P3HT in face-on orientation for EH-IDTBR- and O-IDTBR-based systems can be increased from 18.48 nm to 20.94 nm and 21.67 nm respectively, resulting from the stronger crystallinity of O-IDTBR than that of EH-IDTBR, which was beneficial for charge transport in the vertical direction. These results indicate that selecting the appropriate crystalline non-fullerene acceptors may be an effective strategy to optimize nanomorphology to further achieve high efficiency ternary OSCs.

Binary and ternary organic nanoparticles (NPs) comprising 7,7-(4,4-bis(2-Ethylhexyl)-4H-silolo [3,2-b:4,5-b′]dithiophene-2,6-diyl)bis (6-fluoro-4-(5′-hexyl-[2,2′-bithiophen]-5-yl)benzo-[c] [1,2,5]thiadiazole) (p-DTS(FBTTH2)2), poly (3-hexylthiophene) (P3HT) or/and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) were prepared by precipitation method. The formation of the organic NPs is confirmed by the atomic force microscope (AFM). The absorption spectra show that the blended organic NPs display increased interchain interactions compared to the polymer blends dissolved in the solution. The processes of exciton separation and charge transfer in the organic NPs have been investigated using time-resolved photoluminescence (TRPL) spectroscopy and anisotropy measurements. The results demonstrate that the charge transfer efficiency is improved in the NPs in comparison with that in solution, due to the enhanced interchain interactions and intimate contact between the donor and acceptor materials in NPs. Due to Forster resonance energy transfer (FRET) between P3HT and p-DTS(FBTTH2)2, the photodetectors with ternary NPs in the active layers exhibit improved on/off ratios and enhanced detectivity compared with the binary system, demonstrating the promising applications of organic NPs in the ecofriendly fabrication of organic optoelectronic devices.

Thermally induced fullerene aggregation restricts the long-term stability in organic solar cells. Herein, we demonstrate an effective method of incorporating cross-linkable small-molecule ethoxylated (2) bisphenol-A dimethacrylate (BPA2EODMA) into poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) blends to form an insoluble framework and inhibit fullerene aggregation. The BPA2EODMA exhibits excellent heat and flexural endurance characteristics, which enhance the thermal and morphological stabilities of the active layer. By systematic research with time-resolved optical spectroscopy and microscopy, the morphological changes and charge-transfer dynamics in P3HT:PCBM blends are explored to unravel the underlying mechanisms for improved photovoltaic efficiency by incorporating the cross-linker. The power conversion efficiency (PCE) increased from 3.6 to 4.2% due to the BPA2EODMA incorporation into the active layer, which is ascribed to the enhancement of exciton dissociati...

The vertical phase distribution of components in bulk heterojunction is diversified in organic solar cells (OSCs). The electron donors (acceptors) can be accumulated (depleted) at the interface of active layer and charge extraction layer. The variation of vertical phase distribution significantly influences device performance because of its impact on the charge transport and charge recombination. In order to achieve favorable vertical phase distribution in OSCs based on poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene))-co-(1,3-di(5-thiophene-2-yl)–5,7-bis(2-ethylhexyl) benzo[1,2-c:4,5-c′]dithiophene-4,8-dione)] (PBDB-T):3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))−5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]-dithiophene (ITIC), phenyl-C71-butyric-acid-methyl ester (PC71BM) was incorporated into the binary system to fabricate ternary OSCs. In the ternary blend, PC71BM can effectively regulate the phase distribution of PBDB-T and ITIC in vertical direction, which provides favorable vertical phase distribution for charge transport. Moreover, the addition of PC71BM can also effectively increase the π-π stacking coherence length of both donor and acceptor, which facilitates charge transport and reduces the bimolecular recombination. The addition of an appropriate quantity of PC71BM can obviously improve both fill factor and short-circuit current density of the OSC based on PBDB-T:ITIC while open-circuit voltage reduces only about 0.01 V, which indicates a rational low energy loss. Consequently, the ternary OSC exhibits a best PCE of 11.0% compared to the 9.6% PCE of the binary counterpart.

Wide bandgap non-fullerene acceptors with non-fused conjugated structures play a critical role in organic photovoltaic cells. Here, the non-fullerene acceptors named GS-OEH, GS-OC6 and GS-ISO with the optical bandgaps larger than 1.70 eV are synthesized without using the fused ring structures. Compared with GS-OEH and GS-OC6, GS-ISO exhibits much stronger crystallinity, leading to a smaller energetic disorder and a larger exciton diffusion coefficient. GS-ISO also possesses a higher electroluminescence external quantum efficiency of 1.0×10-2 . The organic photovoltaic cell based on PBDB-TF:GS-ISO demonstrates a power conversion efficiency of 11.62% under the standard one sun illumination. Besides, the PBDB-TF:GS-ISO-based cell with the effective area of 1.0 cm2 exhibits a power conversion efficiency of 28.37% under the 2700 K illumination of 500 lux. The tandem organic photovoltaic cell using PBDB-TF:GS-ISO as the front sub-cell shows an outstanding efficiency of 19.10%. Importantly, the GS-ISO-based organic photovoltaic cell exhibits promising stability under the continuous illumination of the simulated sunlight. This study indicates that the molecular design strategy demonstrated in this work has great superiority in developing non-fused non-fullerene acceptors and also GS-ISO is a promising wide bandgap acceptor for versatile photovoltaic applications. This article is protected by copyright. All rights reserved.

A facile method is proposed to obtain modified shorn graphene oxide (DDAB-sGO) with improved dispersion in organic solvents. Didodecyl dimethylammonium bromide (DDAB)-sGO, which exhibits good dispersibility in the nonpolar solvent o-dichlorobenzene, was obtained via the sono-Fenton reaction and DDAB ionic functionalization. DDAB-sGO was used in the preparation of conjugated polymer:fullerene blend composites. UV–visible absorption spectra, steady-state photoluminescence spectra, fluorescence decay, and grazing incidence X-ray scattering measurements were applied to characterize morphologies, structural features, and charge-transport characteristics of the composites. Doped into poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) conjugated polymer blends, DDAB-sGO is shown to facilitate increased crystallinity and phase separation of PTB7 and PC71BM to achieve a m...

Supramolecular self-assembly of a novel acceptor–π–porphyrin–π–acceptor compound driven by intermolecular sulfur–sulfur interactions leads to the formation of J-aggregates composed of helical nanowire structures. These nanowires have exhibited interesting optical activity, and when utilized as a molecular electron donor with a fullerene acceptor in bulk heterojunction organic solar cells, a high photovoltaic power conversion efficiency of over 8% has been achieved.

Perovskite microplates have important implications in the fields of functional electronics and optoelectronics. We report a facile strategy, antisolvent treatment for the growth of perovskite microplates. The morphology and crystalline quality of the microplates could be controlled by the amount of the chlorobenzene antisolvent used. An appropriate amount of antisolvent facilitates the formation of high-quality perovskite microplates with no residual precursor remaining. Spatially and temporally resolved fluorescence measurements demonstrate the heterogeneity of defect-state density and recombination processes in various perovskite microplate regions. The body center shows higher defect state density when compared with that at the edge or the corner of the microplate. Excessive antisolvent degrades the microplates into smaller particles. The results of this study reveal the factors that influence the crystallization process and photophysical dynamics of perovskite microplates.