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Triplet acceptors have been developed to construct high‐performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T1) are close to those of charge‐transfer states (3CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π‐conjugated core and D‐A structure, were confirmed to be triplet materials, leading to high‐performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D‐A structures result in large spin–orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3CT, facilitating the split of triplet exciton to free charges., Triplet materials are designed by introducing heavy atoms to enhance spin–orbit coupling or constructing donor and acceptor units with a twisted conformation to reduce ΔE ST. However, the twisted materials have not been applied in solar cells due to weak absorption and low charge‐transport mobilities. Now two nonplanar acceptors with large π‐conjugated core were constructed that achieved over 15 % efficiency.

The development of efficient organic sonosensitizers is crucial for sonodynamic therapy (SDT) in the field of cancer treatment. Herein, a new strategy for the development of efficient organic sonosensitizers based on triarylboron-doped acenethiophene scaffolds is presented. The attachment of boron to the linear acenethiophenes lowers the lowest unoccupied molecular orbital (LUMO) energy, resulting in redshifted absorptions and emissions. After encapsulation with the amphiphilic polymer DSPE-mPEG

Broad response organic photodetectors (OPDs) with a photomultiplication (PM) effect are achieved with one absorber layer and one multiplication layer. The response range of the PM-OPDs is primarily determined by materials in the absorber layer, and the external quantum efficiency (EQE) of the PM-OPDs is mainly controlled by the multiplication layer. Here, double-layered PM-OPDs were designed with an ITO/ZnO/PM6:Y6/PC71BM:P3HT (100:5, w/w)/Au structure, where PM6:Y6 is employed as an absorber layer and PC71BM:P3HT is used as a multiplication layer. The optimal PM-OPDs exhibit a broad response covering 350-950 nm. Meanwhile, the optimal PM-OPDs exhibit the largest EQE value of ∼1200% and a maximum specific detectivity (D*) of ∼6.8 × 10-12 cm Hz1/2 W-1 under a 10 V bias. This double-layered approach may be a smart strategy for realizing PM-OPDs with an easily adjustable response range.

A highly electron-deficient dicyanomethylene-bridged triarylborane, FMesB-TCN, was reported with a low-lying LUMO and crystallization-induced emission enhancement in its block-shape crystal. DFT calculations revealed lower re-organization energy of the block crystal than that of the weakly emissive acicular crystal. This work explored a novel boron-containing skeleton with interesting optical properties.

The use of steric hindrance in blue thermally activated delayed fluorophores shows empirically the improvement of operational lifetime for organic light-emitting diodes (OLEDs). Nevertheless, the intrinsic mechanism of this strategy remains unclear and elusive. Here, the steric effects on rate coefficient and degradation probability of bimolecular quenching processes are decoupled by magnetic field effects and quantum-chemical calculation. The respective dependence of magnetoelectroluminescence on triplet density and charge-carrier density indicates that triplet-charge quenching (TCQ) is the dominant degradation mechanism over that of triplet-triplet annihilation, where steric hindrance effectively prevents the occurrence of Dexter-type TCQ and significantly reduces the TCQ rate coefficient. On the contrary, only a slight increase in degradation probability is generated by the steric effect from bulk inert groups. These findings will provide unambiguous guidance for the design of functional materials for OLEDs.

Organic-inorganic hybrid perovskites have attracted great attentions for photovoltaic applications due to impressive energy conversion efficiency and low cost fabrication. This article reports the effect of photogenerated dipoles in the electron transport layer (ETL) on the photovoltaic actions in perovskite solar cells (PSCs). A nonfullerene material ITIC with optically induced dipoles was doped into PCBM acting as ETL in inverted planar structure PSCs (ITO/PEDOT:PSS/MAPbI3-xClx/ETL/PEI/Ag). The power conversion efficiency (PCE) of PSCs increases from 13.48% to 14.52% with introducing ITIC into ETL. The capacitance measurements indicate that optically induced dipoles can decrease interfacial charge accumulation. Furthermore, impedance spectroscopy suggests the charge recombination as well as ionic migration are reduced with ITIC doped ETL. Steady and transient PL spectra reveal that the electron extraction is more efficient with optically induced dipoles in the ETL. These results provide unique design of ETL in perovskite solar cells.

Recent studies have shown that introductions of some organic additives are beneficial for optimizing organic–inorganic hybrid perovskite (OIHP) optoelectronic properties to promote their industrial...

Recent studies have shown that organic-inorganic hybrid perovskites (OIHPs) exhibit unprecedented optoelectronic properties for photovoltaic applications. Complete realizations of photo- and electrically induced surface polarization and recombination are critically important for extensively upgrading solar cell performance. We have explored such effects in a planar solar cell comprising ITO(glass)/PEDOT:PSS/CH3NH3PbI3-xClx/PC60BM/PEI/Ag with a maximum power conversion efficiency (PCE) of 15.4%. A remarkable frequency-dependence of surface polarization was observed for the operating device under illumination (i.e. short-circuit current J s c condition) and at steady state (i.e. open-circuit voltage V o c condition). A sign reversal of the capacitance (i.e. negative capacitance) associated with the surface polarization and recombination was detected at some specific steady states. Based on capacitance-voltage (C-V) spectroscopic measurements and theoretical fittings, they can be understood that, (i) a naturally formed surface depletion region due to energy mismatch can be fully suppressed at a very low fluence and moderate forward bias voltage; (ii) a surface capacitance ( C s ) appears at lower ac-modulation frequencies only; (iii) remarkable trap-assist and band to band surface recombination may play the dominant roles for generating the negative capacitive effect in the CH3NH3PbI3-xClx based photovoltaic system.

The utilization of interfacial transport layers is critically important for extensively elaborating organic photovoltaic efficiencies. Despite some fundamental knowledge regarding their electrical and optical properties, a full realization of their impact on photoactive layers is still lacking. In this work, we report a new insight into the impact of the interfacial transport layers on physical properties of an organic bulk heterojunction (BHJ) system comprising ITO(glass)/PEDOT:PSS/PIDTDTQx:PC70BM/PFN/Al. A combination of multiple measurements was performed either at steady states or at working conditions aiming to deeply understand the role of the interfacial transport layers in the organic BHJ photovoltaics. Experimental results validated our assumption that the optoelectronic properties of the organic blends, such as PIDTDTQx:PC70BM, can be remarkably influenced due to the presence of the electron/hole transport layers. We have looked into this issue by examining the organic blend PIDTDTQx:PC70BM-base...

These days, organic-inorganic hybrid perovskites (OIHP) and non-fullerene acceptor (NFA) molecules are all at the frontiers of research and development in the domain of photovoltaics. A careful design and use of inorganic transparent metal oxides with wide band gaps as electron and hole transport layers are critically important for highly efficient and stable solar cells. As one of the most favorable electron transport materials, tin oxide (SnO

The effect of low-temperature dynamic vacuum annealing (DVA) of sol–gel ZnO films on inverted polymer solar cells (IPSCs), which are composed of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PC61BM), was systematically investigated. The results show that IPSCs with low-temperature DVA-based ZnO films exhibit 15.9% enhancement within a power-conversion efficiency (PCE) of 4.01%, compared with IPSCs with conventional annealing-process-based ZnO films. The surface morphology measurement of ZnO films, light intensity dependent solar cell behaviors, and impedance spectroscopy of devices were investigated to study the performance of IPSCs. The dramatic enhancement of PCE was attributed to the improved surface morphology, optimized carrier transport characteristics, prolonged charge carrier lifetime, and reduced recombination rate. These results indicate that the low-temperature DVA process could be a promising method for producing high-quality ZnO films and high-performance IPSCs.

Organic nonfullerene acceptors (NFA) have received tremendous research interests due to the efficient interfacial charge transfer (CT) when they combine with polymeric donors. It is of critical importance to unravel, to which extent, spin-dependent excited states, energetic disorder and photo-induced polarization are essentially correlated, and eventually contribute for the photovoltaic action. Herein, we explore them in a polymer-NFA ITTC based organic bulk heterojunction (BHJ) solar cell. With assist of magneto-photocurrent measurements at the short-circuit current density (Jsc) condition and steady state impedance spectroscopic measurements, the dominant mechanism for the Jsc generation is governed by the triplet-charge reaction. We postulate that long lived triplets are more likely to interact with trapped charges at excited states, giving rise to Jsc. It turns out that the trap states may not always act as passive role for the energy loss in the organic photovoltaic system. More importantly, both applied bias voltage and light can effectively manipulate the magnitude and sign of the magneto-photocurrent. By quenching the photo-generated build-in field, the bias-dependent magneto-photocurrent evidently proves the efficient dissociation of polaron pairs at CT states. In particular, the photo-excitation wavelength has strong impact on the hyperfine field. Lastly, we demonstrate that the double beam photo-excitation generated dipole-dipole interaction assists for the electron-hole dissociation. Our work may pave the way for understanding the inside spin- and photo-physical phenomena in the NFA based organic photovoltaic system.

The broadband organic photodetectors (OPDs) with photomultiplication (PM) phenomenon are fabricated by using Y6 doped with rather less PBDB-T as active layers having electron-only transport characteristic. The PM-OPDs with PBDB-T:Y6 (3:100, wt/wt) as active layers exhibit the external quantum efficiency (EQE) of 18,000% at 350 nm and 15,000% at 870 nm under 1 V bias. The PM-OPDs exhibits a broad spectral response range from 320 to 950 nm, which is mainly determined by the trapped hole distribution near Al electrode. The working mechanism of PM-OPDs should be attributed to interfacial trap-assisted electron tunneling injection, which can be further confirmed from the EQE spectral shape of PM-OPDs with different active layer thickness. The n-type polymer PZ1 was selected as interfacial layer to be inserted between PEDOT:PSS and active layers, which makes PM-OPDs with PZ1 interfacial layer work well under forward and reverse bias. This work may provide a smart strategy to achieve broadband PM-OPDs by adjusting the distribution of trapped charge near electrode.

Methylammonium lead iodide (CH

Methylammonium lead iodide (CH3NH3PbI3), with the organic-inorganic hybrid perovskite (OIHP) structure, has gained tremendous research interest due to its excellent photo-electron conversion ability in the application of photovoltaics. Despite its solution processed polycrystalline thin film form in solar cells, the single crystalline counterpart may offer some incredibly novel optoelectronic functionalities. In this work, a sizable (>5 mm) and high quality CH3NH3PbI3 single crystal has been synthesized by the inverse temperature crystallization method, and a white-light photodetector of the structure glass/ITO/Ga/ CH3NH3PbI3/Au was fabricated. Overbroad photo-excitation intensities ranging from 0.1 mW/cm2 to 100 mW/cm2 using a sun-light simulator, the on-off ratio is tunable in a wide-range from 65 to 2250 at zero bias voltage. The responsivity (R) and detectivity (D*) are 36.2 mA/W and 2.68×1011 Jones respectively at a weak white-light intensity such as 0.1 mW/cm2. Both the photodetective parameters decrease with the increase of the illumination intensity. Based on impedance spectra obtained at working condition and light intensity dependent Jsc measurements, the surface trap-assist recombination may play a dominating role. The corresponding lifetime (τsurf) and resistance (Rsurf_trap) exhibit fast decays at higher illumination intensities. This fundamental study may pave the way for exploring the contribution of the surface trap-assist recombination in the CH3NH3PbI3 single crystal based photodetector. We believe it is applicable for integration in micro-photonics for sensitive and weak white-light photo-detection.