Solution-processed Devices Research Articles

Pyro-phototronic effect in colloidal quantum dots on silicon heterojunction for high-detectivity infrared photodetectors

Solution-processed colloidal quantum dots (CQDs) have attracted significant interest for infrared photodetection, particularly due to their easy integration with silicon-based electronics. Among these, silver sulfide (Ag2S) CQDs stand out as non-toxic infrared semiconductors. However, their application in photodetectors has traditionally shown lower detectivity compared to devices based on lead sulfide and mercury telluride CQDs. Here we demonstrate report Ag2S CQD/silicon p-n heterojunction photodetectors that exhibit substantially enhanced detectivity. This improvement was facilitated by the pyro-phototronic effect (PPE) in Ag2S CQDs, which significantly increases the photocurrent. Consequently, the detectivity of the CQD/silicon photodetector was improved by a factor of 17, reaching 4.1×1010 Jones at 980 nm. These findings pave the way for new opportunities in utilizing CQDs for pyro-phototronic driven, solution-processed optoelectronic devices.

Hybrid Local and Charge Transfer Emitters Utilizing Hyperconjugation Effect Towards Solution-Processed Ultra-Deep-Blue OLEDs with External Quantum Efficiency Approaching 12.

Hybrid local and charge transfer (HLCT) excited state materials, which possess weak donor-acceptor (D-A) pure organic structures, deserve one of the most promising efficient and stable blue emitters. Through high-lying reverse intersystem crossing (hRISC) process, 75% triplet excitons generated by electrical excitation could be harvested and utilized in organic light-emitting diodes (OLEDs). However, there are still significant challenges to achieve high-efficiency ultra-deep-blue HLCT emitters with low Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinate y values. Here, a series of novel blue HLCT emitters based on spiro[1,8-diazafluorene-9,2'-imidazole] structure were designed and synthesized by fine-tuning the spiro[fluorene-9,2'-imidazole] core structure in our previous work through heteroatom substitution and hyperconjugation effect. The target emitters were endowed with excellent photophysical and electrochemical merits, thermal stability and solution processibility. The solution-processed OLED device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[1,8-diazafluorene-9,2'-imidazole] (NFIP-CZ) achieved efficient ultra-deep-blue emission (CIEx,y = 0.1581, 0.0422) with the maximum external quantum efficiency (EQEmax), maximum current efficiency (CEmax) and maximum power efficiency (PEmax) of 11.94%, 4.07 cd·A-1 and 2.56 lm·W-1. The record EQE is a breakthrough in both solution-processed and vacuum vapor deposition ultra-deep-blue HLCT-OLEDs currently.

Molecular Design and Synthetic Approaches for the Realization of Multichannel Radiative Decay Pathways in Gold(III) Complexes and Their Applications in Organic Light-Emitting Devices.

A unique class of tridentate diaryltriazine ligand-containing gold(III) complexes with thermally activated delayed fluorescence (TADF) and/or thermally stimulated delayed phosphorescence (TSDP) properties has been designed and synthesized. With a simple structural modification on the coordination of carbazole moiety in the monodentate ligand, a large spectral shift of ∼160 nm (ca. 4900 cm-1) spanning from sky blue to red emissions has been demonstrated in solid-state thin films. Three-state or four-state models have been employed in fitting the emission lifetimes of the gold(III) complexes at various temperatures. The findings clearly indicate the presence of three emitting states, S1, T1, and T1', suggesting the coexistence of TADF, phosphorescence, and TSDP. Notably, a minor structural change in the donor moiety between phenylcarbazolyl and diphenylaminoaryl has been demonstrated to turn on/off the TSDP, resulting in TADF-TSDP-phosphorescence or TADF-phosphorescence emitters. The TADF and/or TSDP properties have also been supported by temperature-dependent ultrafast transient absorption studies, with the direct observation of reverse intersystem crossing (RISC) and reverse internal conversion (RIC) and the determination of the activation parameters and excited state dynamics. Solution-processed and vacuum-deposited organic light-emitting devices (OLEDs) have been prepared, in which sky blue emitting devices based on 5 exhibit an operational lifetime LT70 ∼ 5 times longer than the previously reported sky blue emitting analogue that shows only TSDP property. These results have provided valuable insights into the manipulation of the excited states via rational molecular design toward the realization of gold(III)-based TSDP and/or TADF materials with multiple radiative decay pathways that show enhanced radiative decay rate constants (kr) for practical OLED applications.

Surface treatment processed electron transport layers for efficient Sb2S3 solar cells

Solution-processed Sb2S3 thin films and solar cell devices have recently gained popularity due to their easy procedure and outstanding final device performance. Nevertheless, although the substrate has a significant influence on thefollowing functional films, the effect of the substrate in the Sb-based solar cells appears to have not been adequately examined. In this study, we performed an interesting thioacetamide (TA)-assisted surface treatment strategy on the electron transport layer (ETL) to achieve high-quality development of Sb2S3 thin films and based solar devices. The surface treatment of ETLs resulted in a uniform surface, Zn(OH)2 impurity reduction, and excellent wettability. The above enhanced the growth of Sb2S3 thin films with features like extremely large crystal sizes (∼8 um), more homogeneous and dense film morphology, preferred crystal orientation, reduced oxygen content, and fewer defects, which benefits carrier transport. Finally, a device structure constructed of FTO/TiO2/Zn(O,S)/Sb2S3/Spiro/Au was created, resulting in an almost 30 % increase in efficiency, from 4.05 % to 5.21 %. The proposed approach not only gives new insights into generating higher-quality Sb2S3 thin films and devices, but it also presents new concepts and methods for future high-quality sulfide thin film preparation.

Optical Applications of CuInSe2 Colloidal Quantum Dots.

The distinctive chemical, physical, electrical, and optical properties of semiconductor quantum dots (QDs) make them a highly fascinating nanomaterial that has been extensively studied. The CuInSe2 (CIS) QDs demonstrates great potential as a nontoxic alternative to CdSe and PbSe QDs for realizing high-performance solution-processed semiconductor devices. The CIS QDs show strong light absorption and bright emission across the visible and infrared spectrum and have been designed to exhibit optical gain. The special characteristics of these properties are of great significance in the fields of solar energy conversion, display, and electronic devices. Here, we present a comprehensive overview of the potential applications of colloidal CIS QDs in various fields, with a particular focus on solar energy conversion (such as QD solar cells, QD-sensitized solar cells, and QD luminescence solar concentrators), solar-to-hydrogen production (such as photocatalytic and photoelectrochemical H2 production), and QD electronics (such as QD transistors, QD light-emitting diodes, and QD photodetectors). Furthermore, we offer our insights into the current challenges and future opportunities associated with CIS QDs for further research.

Optical, Photophysical, and Electroemission Characterization of Blue Emissive Polymers as Active Layer for OLEDs.

Polymers containing π-conjugated segments are a diverse group of large molecules with semiconducting and emissive properties, with strong potential for use as active layers in Organic Light-Emitting Diodes (OLEDs). Stable blue-emitting materials, which are utilized as emissive layers in solution-processed OLED devices, are essential for their commercialization. Achieving balanced charge injection is challenging due to the wide bandgap between the HOMO and LUMO energy levels. This study examines the optical and photophysical characteristics of blue-emitting polymers to contribute to the understanding of the fundamental mechanisms of color purity and its stability during the operation of OLED devices. The investigated materials are a novel synthesized lab scale polymer, namely poly[(2,7-di(p-acetoxystyryl)-9-(2-ethylhexyl)-9H-carbazole-4,4'-diphenylsulfone)-co-poly(2,6-diphenylpyrydine-4,4'-diphenylsulfone] (CzCop), as well as three commercially supplied materials, namely Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), poly[9,9-bis(2'-ethylhexyl) fluorene-2,7-diyl] (PBEHF), and poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (F6PC). The materials were compared to evaluate their properties using Spectroscopic Ellipsometry, Photoluminescence, and Atomic Force Microscopy (AFM). Additionally, the electrical characteristics of the OLED devices were investigated, as well as the stability of the electroluminescence emission spectrum during the device's operation. Finally, the determined optical properties, combined with their photo- and electro-emission characteristics, provided significant insights into the color stability and selectivity of each material.

Symmetry-Broken Electronic State of CsPbBr3 Cubic Perovskite Nanocrystals.

The development of densely packed, self-assembled perovskite nanocrystals (PeNCs) with a favorable transition dipole moment (TDM) orientation is crucial for their application in solution-processable electronic devices. In this study, we fabricated anisotropic CsPbBr3 PeNCs with a symmetry-broken electronic state on quartz substrates modified by 3-aminopropyltrimethoxysilane (APS). Densely packed and self-assembled monolayers of cubic PeNCs were formed on the substrates by using a dip coating technique. The angle-dependent absorption and photoluminescence (PL) spectra confirmed that the PeNC monolayer on the APS-treated substrate exhibited anisotropic electronic states in the in-plane and out-of-plane directions of the substrate. In contrast, when the quartz substrate was modified with the long alkyl silane coupling agent, octadecyltrimethoxysilane, the absorption and PL spectra exhibited no angular dependence, indicating the absence of anisotropy. Experimental and simulated results confirmed the presence of vertical TDMs in the densely packed PeNCs on the APS-treated substrate, which could be attributed to the effect of the amino groups of the APS on the facet of the cubic PeNCs facing the quartz substrate. Hence, surface chemical modifications of the substrate can aid in the precise control of the symmetry of the electronic states and TDM orientation in cubic PeNCs. These findings can promote the development of densely packed, high-coverage PeNC films with a controllable TDM orientation for applications in electronic devices such as solar cells, sensors, and light-emitting diodes.

Cascade Effect of a Dimerized Thermally Activated Delayed Fluorescence Dendrimer.

Thermally activated delayed fluorescence (TADF) emitters with a high horizontal orientation are highly essential for improving the external quantum efficiency (EQE) of organic light-emitting diodes; however, pivotal molecular design strategies to improve the horizontal orientation of solution-processable TADF emitters are still scarce and challenging. Herein, a phenyl bridge is adopted to connect the double TADF units, and generate a dimerized TADF dendrimer, D4CzBNPh-SF. Compared to its counterpart with a single TADF unit, the proof-of-the-concept molecule not only exhibits an improved horizontal dipole ratio (78 %) due to the π-delocalization-induced extended molecular conjugation, but also displays a faster reversed intersystem crossing rate constant (6.08×106 s-1) and a high photoluminescence quantum yield of 95 % in neat film. Consequently, the non-doped solution-processed device with D4CzBNPh-SF as the emitter achieves an ultra-high maximum EQE of 32.6 %, which remains at 26.6 % under a luminance of 1000 cd/m2. Furthermore, when using D4CzBNPh-SF as a sensitizer, the TADF-sensitized fluorescence device exhibits a high maximum EQE of 30.7 % at a luminance of 575 cd/m2 and a full width at half maximum of 36 nm.

Machine Learning-Inspired Molecular Design, Divergent Syntheses, and X-Ray Analyses of Dithienobenzothiazole-Based Semiconductors Controlled by S⋅⋅⋅N and S⋅⋅⋅S Interactions.

Inspired by the previous machine-learning study that the number of hydrogen-bonding acceptor (NHBA) is important index for the hole mobility of organic semiconductors, seven dithienobenzothiazole (DBT) derivatives 1 a-g (NHBA=5) were designed and synthesized by one-step functionalization from a common precursor. X-ray single-crystal structural analyses confirmed that the molecular arrangements of 1b (the diethyl and ethylthienyl derivative) and 1c (the di(n-propyl) and n-propylthienyl derivative) in the crystal are classified into brickwork structures with multidirectional intermolecular charge-transfer integrals, as a result of incorporation of multiple hydrogen-bond acceptors. The solution-processed top-gate bottom-contact devices of 1b and 1c had hole mobilities of 0.16 and 0.029 cm2 V-1s-1, respectively.

Synchrotron Radiation-Based In Situ GIWAXS for Metal Halide Perovskite Solution Spin-Coating Fabrication.

Solution-processable perovskite-based devices are potentially very interesting because of their relatively cheap fabrication cost but outstanding optoelectronic performance. However, the solution spin-coating process involves complicated processes, including perovskite solution droplets, nucleation of perovskite, and formation of intermediate perovskite films, resulting in complicated crystallization pathways for perovskite films under annealing. Understanding and therefore controlling the fabrication process of perovskites is difficult. Recently, synchrotron radiation-based in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) techniques, which possess the advantages of high collimation, high resolution, and high brightness, have enabled to bridge complicated perovskite structure information with device performance by revealing the real-time crystallization pathways of perovskites during the spin-coating process. Herein, the developments of synchrotron radiation-based in situ GIWAXS are discussed in the study of the crystallization process of perovskites, especially revealing the important crystallization mechanisms of state-of-the-art perovskite optoelectronic devices with high performance. At the end, several potential applications and challenges associated with in situ GIWAXS techniques for perovskite-based devices are highlighted.

Emulating Low-Power Synaptic Plasticity in a Solution-Processed Oxide-Based Long Retention Memory Transistor with High Learning Accuracy.

The exploration of synaptic plasticity in metal-oxide-based ferroelectric thin-film transistors has been limited. As a perovskite ferroelectric material, LiNbO3 is widely studied; but its potential use as a neuromorphic device, like synaptic transistors, has not been realized. In this study, a solution-processed ferroelectric thin-film transistor (FeTFT) with an alternating layer of LiNbO3 and Li5AlO4 as a gate dielectric has been fabricated. This configuration reduces the depolarization field by leveraging the large ionic polarization of Li+ ions in the Li5AlO4 layer, while the wide bandgap helps mitigate the leakage current. FeTFT exhibits impressive transistor performance, including a saturation mobility of 0.478 cm2V-1 s-1, an on/off ratio of 3.08 × 103, and a low trap-state density of 1.3 × 1013 cm-2. Moreover, the device demonstrates good memory retention, retaining information for nearly 1 day. It successfully emulates synaptic plasticity, specifically short-term plasticity and long-term plasticity. Besides, a 94% training accuracy has been achieved through artificial neural network simulation. Notably, the FeTFT consumes minimal power, with energy consumption of approximately 3.09 nJ per synaptic event, which is remarkably low compared to other reported solution-processed FeTFT devices.

Narrowband absorption far-red organic photodetector for photoplethysmography.

Narrowband absorption organic semiconductors are highly attractive for spectrally selective photodetection applications requiring lightweight and customizable devices. Although narrowband absorption photodetectors have achieved success in the visible range, far-red (650-750 nm) devices are scarce. The far-red wavelength range is relevant for applications in medical diagnostics, such as photoplethysmography for blood oxygen saturation detection. In this study, a non-fullerene bulk heterojunction organic photodetector with a narrowband response in the far-red spectrum is fabricated. The photodetector exhibits a high detectivity of 5.06 × 1012 Jones at a bias of -2 V. The full-width at half-maximum of the responsivity peak of the photodetector is 85 nm, which is the smallest spectral width among solution-processed devices. The response speed is 11.56 kHz. The photodetector responds within the microsecond range. The potential of the photodetector for blood oxygen saturation measurement is demonstrated.

Impact of the alkyl side-chain length on solubility, interchain packing, and charge-transport properties of amorphous π-conjugated polymers

Increasing the length of alkyl side chains is a typical way to improve the solubility of π-conjugated polymers designed for use in solution-processed devices. However, these modifications have also been reported to alter the film morphology. Given that the mechanism leading to improved solubility is not well documented yet and the nanoscale (local) morphologies of amorphous π-conjugated polymer films are difficult to characterize experimentally, here, we combine molecular dynamics simulations and long-range corrected density functional theory calculations to examine at the molecular scale the impact that the alkyl side-chain length has on polymer solubility and film morphologies. As a representative example, we consider poly(thieno[3,4-c]pyrrole-4,6-dione-alt-3,4-difluorothiophene) (PTPD[2F]T) with two different lengths of the alkyl side chains on the thieno[3,4-c]pyrrole-4,6-dione (TPD) moieties, i.e., 2-hexyldecyl (2HD) and 2-decyltetradecyl (2DT). A detailed analysis of polymer–solvent and polymer–polymer interactions provides a picture that describes the underlying mechanism for improved solubility in going from 2HD to 2DT. We then underline an intrinsic characteristic that decreasing the side-chain length brings a greater extent of backbone planarity and lesser side chain-TPD interactions, which leads to higher interchain π-π packing density and order, while the interchain π-π packing patterns remain similar in the two films. These morphologies are discussed in terms of the charge-transport properties between neighboring PTPD[2F]T chains, which point to a higher electron mobility in the PTPD[2F]T films with shorter alkyl side chains. Overall, our findings offer guidance in the field of solution-processed electronic devices by pointing out that the polymer alkyl side-chain length could be minimized to improve carrier mobility while ensuring polymer solubility.

Polar solvent vapor annealing enhanced optoelectronic properties of solution-processed exciplex organic light-emitting diodes.

Exciplex organic light-emitting diodes (OLEDs) are widely utilized for their high internal quantum efficiency. Although solution-processed devices offer the advantages of simple operation and low cost, few studies have reported on the preparation of exciplex OLED devices using solution methods. This paper presents exciplex OLEDs produced between m-MTDATA and Bphen, fabricated using a solution method and optimized by a polar solvent vapor annealing (PSVA) treatment. Unlike other approaches applied to the transport layer, PSVA treatment was conducted on the exciplex-based light-emitting layer, resulting in successful enhancement of the photoelectric properties of both the light-emitting layer film and OLEDs, thereby achieving the anticipated objective. Optimized performance of exciplex OLEDs was achieved after the emission layer was PSVA treated for 20 min. The maximum luminescence intensity increased by a factor of ∼4 compared to a control device without PSVA treatment. An analysis of charge carrier mobility and impedance spectroscopy also indicated the inevitable presence of interface resistance when PSVA was applied to the exciplex emission layer. However, the total resistance (including interface and bulk resistances) was reduced to a minimum after a 20-minute PSVA treatment. Therefore, higher electron mobility and lower lighting voltage are obtained. The enhanced optoelectronic properties of exciplex OLEDs could be attributed to the PSVA treatment, which induced an alignment of polar molecules and enhanced electron mobility.

(Invited) Assembly of Carbon Nanotubes Heterostructures Down to Single-Particle Control

We will present different chemical strategies for the in-solution assembly of single walled carbon nanotube (SWCNT)-based heterostructures, down to single-particle control and resolution. In particular, we interfaced SWCNTs to inorganic semiconducting nanoparticles and nanocrystals, perovskites, as well as metal nanoparticles and nanowires. We developed various approaches towards this end, from the selective and differential functionalisation of CNTs terminal ends with distinct individual nanomoieties , to the use of nanotubes as templates for the growth of nanomaterials on their sidewall or in their cavity. Solution-processed optoelectronic devices were fabricated employing the aforementioned nanohybrids, displaying various sensitivity to a broad range of illumination wavelengths.

Thermally activated delayed fluorescence dendrimers with strategic dendrons to construct highly efficient solution-processed OLEDs

For the promising merits of the precise molecular structures and the satisfactory dissolvability, Thermally activated delayed fluorescence (TADF) dendrimers are turning into the attractive candidates for fully solution-processed organic light-emitting diodes (OLEDs). However, the rational design of TADF dendrimers with strategic dendrons for improving the efficiency and decreasing efficiency roll-off is still challenging. Here, two TADF dendrimers, (4S,5R)-2,4,5,6-tetrakis(4-((6-((9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)oxy)hexyl)oxy)-9H-carbazol-9-yl)isophthalonitrile (G-O-mCP) and (4S,5R)-2,4,5,6-tetrakis(4-((6-(3,5-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)phenoxy)hexyl)oxy)-9H-carbazol-9-yl)isophthalonitrile (G-O-DPBi) were developed and synthesized by integrating the peripheral strategic dendrons with the emissive core through nonconjugated alkoxy chains. Impressively, the peripheral dendron of G-O-mCP possessing the superior hole-transporting capability belongs to the electron-donor category and the peripheral dendron of G-O-DPBi with the admirable electron-transporting capability belongs to the electron-acceptor category. The elaborate regulation of the different dendrons with solubilizing groups is beneficial for restraining the aggregation-caused quenching (ACQ) effect and balancing the carrier transport capability. Consequently, the fully solution-processed device based on G-O-mCP realized the maximum external quantum efficiency (EQE) of 19.98 %. In addition, the formation of the interfacial exciplex endows the solution-processed device with a extremely low turn-on voltage (Von) of 2.7 V and a high power efficiency (PE) of 43.80 lm/W, which is among the highest power efficiency of the reported TADF-OLEDs.

Arylimidazole-terminated phenylene ethynylene molecules as organic luminescent materials

Three phenylene ethynylene derivatives substituted by arylimidazole groups (benzo[d]imidazole, phenanthro[9,10-d]imidazole and pyreno[4,5-d]imidazole) at both ends were successfully synthesized and characterized for organic electroluminescence devices. The photophysical, electrochemical, and thermal stability of the compounds were systematically investigated to reveal their structure-property relationships. All compounds presented a X-shaped structure, and exhibited excellent thermal stability and intense emission in solution and solid states. Furthermore, the solution-processed doped devices using the blend of tris(4-carbazoyl-9-ylphenyl)amine (TCTA) with the phenylene ethynylene derivatives as emitting layers emitted deep-blue emission with maximum external quantum efficiency (EQEmax) of 0.63 % for the benzo[d]imidazole-terminated derivative and blue emission with EQEmax of 1.93 % and 1.45 % for the phenanthro[9,10-d]imidazole- and pyreno[4,5-d]imidazole-terminated derivatives, respectively, suggesting that these compounds have a great potential as the organic emitters for deep-blue and blue devices.

Manipulating the photophysical properties of multi-donor molecules for fast reverse intersystem crossing in solution-processed OLED devices

The slow reverse intersystem crossing (RISC) rate in thermally activated delayed fluorescence (TADF) emitters result in extended exciton lifetime and pronounced efficiency loss at high luminance level. To address this limitation, we have developed and characterized a series of novel compounds featuring triazine cores substituted with tert-butyl carbazole moieties at various positions and quantities. The objective here is to fine-tune the charge transfer properties, thereby enhancing the efficiency of the RISC process. Our studies reveal that through-space charge transfer is more effective than long-range through-bond charge transfer in minimizing the singlet-triplet energy gap and accelerating RISC. The optimized compound, 4tCzTrz, exhibits an exceptionally fast RISC rate of 1.02 × 107 s−1 and a high photoluminescence quantum yield of up to 100 %. Solution-processed organic light-emitting diodes (OLEDs) incorporating this molecule have achieved outstanding maximum external quantum efficiencies of around 20 %, whether used as an emitter directly or as a sensitizer to boost overall emission efficiency.

Enable strong electrical coupling between the InZnP@PbS collodial quantum dots in films via the two-step ligand exchange method

Colloidal quantum dots (CQDs) are promising materials for building next-generation solution-processed, high-performance, and low-cost optoelectronic devices. The photoelectric properties of the resulting films are not only determined by the intrinsic characteristics of the CQDs but are also significantly affected by the electrical coupling between them. However, enhancing the electrical coupling in CQD-based films is still a big challenge. In this work, a two-step ligand exchange strategy has been conducted to solve the above issue, where the InZnP@PbS CQDs have been used as the case. First, the Meerwein salt (Et3OBF4) solution in N, N-dimethylformamide (DMF) has been employed to peel off the native ligands that are strongly capped on the surface of oil-soluble CQDs, resulting in a neat surface. Second, iodide ions are linked to the neat surface of the CQDs to narrow the distance between them and passivate their defects, establishing strong electrical coupling. Transient surface photovoltage (TSPV) and photo-conductance tests confirm that the resulting InZnP@PbS–I CQDs films possess good photoelectric properties and stability. In the fabricated solid-state solar cells, 3.1 % of the photoelectric conversion efficiency (PCE) has been achieved under 1 sun. The current results are outstanding for III-V group CQD-based all solid-state solar cells.

High-performance solution-processed blue OLEDs based on “hot exciton” materials

“Hot exciton” luminescent materials are being researched as potential candidates for application in OLEDs due to their ability to undergo high-level reverse intersystem crossing (hRISC). While evaporated OLEDs using “hot exciton” luminescent materials have shown impressive efficiency, there is a dearth of information on solution-processed “hot exciton” OLEDs, specifically in the realm of deep blue OLEDs. In this work, we developed novel solution-processed blue OLEDs by employing “hot exciton” material, 2-(4-(10-(3-(9H-carbazol-9-yl)phenyl) anthracen-9-yl)phenyl)-1-phenyl-1H-phenanthro [9,10-d] imidazole (PAC), as the luminescent material and host material (the classical fluorescent material BD as a guest). An improvement to the quantum efficiency of the luminescent layer was achieved by incorporating a hole transport layer (PVK) between the hole injecting layer (PEDOT:PSS:PFI) and the luminescent layer. Finally, the resultant non-doped blue OLED achieved EQEmax and EUEmax of 4.5 % and 56.3 %, respectively, while the doped blue OLED showed EQEmax and EUEmax of 5.3 % and 54.8 %, respectively. The efficiency roll-off at a brightness of 1000 cd m−2 for the doped device was 11.5 %, whereas for the non-doped device was only 4.2 %. Analysis of the magneto-electroluminescence and transient EL decay suggests that the high EUE in the solution-processed devices primarily derives from the “hot exciton” process. This study confirms that “hot exciton” materials can serve as a key factor in achieving efficient solution-processed blue OLEDs through a well-designed device architecture.