Jiang Huang

Highly Efficient Organic Solar Cells with Improved Vertical Donor-Acceptor Compositional Gradient Via an Inverted Off-Center Spinning Method.

A novel, yet simple solution fabrication technique to address the trade-off between photocurrent and fill factor in thick bulk heterojunction organic solar cells is described. The inverted off-center spinning technique promotes a vertical gradient of the donor-acceptor phase-separated morphology, enabling devices with near 100% internal quantum efficiency and a high power conversion efficiency of 10.95%.

Nonfullerene Tandem Organic Solar Cells with High Open‐Circuit Voltage of 1.97 V

Small-molecule nonfullerene-based tandem organic solar cells (OSCs) are fabricated for the first time by utilizing P3HT:SF(DPPB)4 and PTB7-Th:IEIC bulk heterojunctions as the front and back subcells, respectively. A power conversion efficiency of 8.48% is achieved with an ultrahigh open-circuit voltage of 1.97 V, which is the highest voltage value reported to date among efficient tandem OSCs.

Highly Efficient Organic Solar Cells Consisting of Double Bulk Heterojunction Layers

An organic solar cell (OSCs) containing double bulk heterojunction (BHJ) layers, namely, double-BHJ OSCs is constructed via stamp transferring of low bandgap BHJ atop of mediate bandgap active layers. Such devices allow a large gain in photocurrent to be obtained due to enhanced photoharvest, without suffering much from the fill factor drop usually seen in thick-layer-based devices. Overall, double-BHJ OSC with optimal ≈50 nm near-infrared PDPP3T:PC71 BM layer atop of ≈200 nm PTB7-Th:PC71 BM BHJ results in high power conversion efficiencies over 12%.

Achieving 12.8% Efficiency by Simultaneously Improving Open-Circuit Voltage and Short-Circuit Current Density in Tandem Organic Solar Cells

Tandem organic solar cells (TOSCs), which integrate multiple organic photovoltaic layers with complementary absorption in series, have been proved to be a strong contender in organic photovoltaic depending on their advantages in harvesting a greater part of the solar spectrum and more efficient photon utilization than traditional single-junction organic solar cells. However, simultaneously improving open circuit voltage (Voc ) and short current density (Jsc ) is a still particularly tricky issue for highly efficient TOSCs. In this work, by employing the low-bandgap nonfullerene acceptor, IEICO, into the rear cell to extend absorption, and meanwhile introducing PBDD4T-2F into the front cell for improving Voc , an impressive efficiency of 12.8% has been achieved in well-designed TOSC. This result is also one of the highest efficiencies reported in state-of-the-art organic solar cells.

Preparation of Reduced Graphene Oxide:ZnO Hybrid Cathode Interlayer Using In Situ Thermal Reduction/Annealing for Interconnecting Nanostructure and Its Effect on Organic Solar Cell

A novel hybrid cathode interlayer (CIL) consisting of reduced graphene oxide and zinc oxide (ZnO) is realized in the inverted organic solar cells (OSCs). A dual-nozzle spray coating system and facile one-step in situ thermal reduction/annealing (ITR/ITA) method are introduced to precisely control the components of the CIL, assemble ZnO with graphene oxide, and reduce graphene oxide into in situ thermal reduced graphene oxide (IT-RGO), simultaneously. The ZnO:IT-RGO hybrid CIL shows high electric conductivity, interconnecting nanostructure, and matched energy level, which leads to a significant enhancement in the power conversion efficiency from 6.16% to 8.04% for PTB7:PC71BM and from 8.02% to 9.49% for PTB7-Th:PC71BM-based OSCs, respectively. This newly developed spray-coated ZnO:IT-RGO hybrid CIL based on one-step ITR/ITA treatment has the high potential to provide a facile pathway to fabricate the large-scale, fast fabrication, and high performance OSCs.

Three-dimensional molecular donors combined with polymeric acceptors for high performance fullerene-free organic photovoltaic devices

Non-fullerene acceptor based organic photovoltaic devices (OPVs) reported so far are inferior to those derived from fullerenes. This increases the speculation on whether donors need to be tailored for advancing non-fullerene OPVs. We explored herein two direct arylation-derived diketopyrrolopyrrole (DPP)-based three-dimensional (3D) donors that can deliver respectable power conversion efficiencies (PCEs) of 4.64% and 4.02% with polymeric acceptor N2200 blends, surpassing those obtained from PC71BM (3.56% and 3.22%, respectively). It is found that these 3D-shaped molecular donors can yield improved photo-to-current conversion and balanced charge transport when blending with the linear N2200 polymer. This finding suggests that engineering molecular geometry can be a promising approach for developing high-performance materials.

Color-tunable and high-efficiency organic light-emitting diode by adjusting exciton bilateral migration zone

A voltage-controlled color-tunable and high-efficiency organic light-emitting diode (OLED) by inserting 16-nm N,N′-dicarbazolyl-3,5-benzene (mCP) interlayer between two complementary emitting layers (EMLs) was fabricated. The OLED emitted multicolor ranging from blue (77.4 cd/A @ 6 V), white (70.4 cd/A @ 7 V), to yellow (33.7 cd/A @ 9 V) with voltage variation. An equivalent model was proposed to reveal the color-tunable and high-efficiency emission of OLEDs, resulting from the swing of exciton bilateral migration zone near mCP/blue-EML interface. Also, the model was verified with a theoretical arithmetic using single-EML OLEDs to disclose the crucial role of mCP exciton adjusting layer.

Modulate Organic-Metal Oxide Heterojunction via [1,6] Azafulleroid for Highly Efficient Organic Solar Cells.

By creating an effective π-orbital hybridization between the fullerene cage and the aromatic anchor (addend), the azafulleroid interfacial modifiers exhibit enhanced electronic coupling to the underneath metal oxides. High power conversion efficiency of 10.3% can be achieved in organic solar cells using open-cage phenyl C61 butyric acid methyl ester (PCBM)-modified zinc oxide layer.

Effect of Hole Transport Layers on the Performance of Organic Optoelectronic Devices based on PBDB-T:ITIC Bulk Heterojunction

In this work, the organic optoelectronic devices with both photovoltaic and detection performance were fabricated based on a blend of the polymer poly[(2,6-(4,8-bis(5-(2ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl-5’,7’-bis(2ethylhexyl)benzo [1’,2’-c:4’,5’-c’]dithiophene-4,8-dione))] (PBDB-T) with the non-fullerene acceptor of 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4hexylphenyl)-dithieno [2,3-d:2’,3’-d’]s-indaceno[1,2-b:5,6-b’] dithio-phene) (ITIC). Meanwhile, the different hole transport layers (HTL) materials of N,N’-bis-(1-naphthyl)-N,N’-diphenyl-1,1’biphenyl-4,4’-diamine (NPB) and N,N’-diphenyl-N,N’-bis(3-methyllphenyl)-(1,1’-biphen-yl)-4,4’diamine (TPD) were adopted to modify the interface of organic active layer and Ag/MoO3 electrode. The result showed that without thermal annealing of PBDB-T:ITIC, the photovoltaic device with TPD HTL exhibited an improvement in power conversion efficiency (PCE) from 4.45% to 5.26% compared with the control device without HTL. Moreover, by analyzing the dark current behavior after thermal annealing, it was found that the TPD HTL could effectively suppress the leakage current from Ag/MoO3 electrode to the active layer. As a result, an efficient organic photo detector with a detectivity of 3.87×10 10 Jones was achieved. Introduction Over the past decades, most bulk-heterojunction (BHJ) organic optoelectronic devices use fullerene derivative materials as the electron acceptors and yield high photovoltaic and detective performance with advantages of light weight, flexibility and low-cost [1-3]. However, fullerene materials have disadvantages such as weak absorption of sunlight and low tunability of electronic energy levels. Those limitations offer a rapid developmental opportunity of non-fullerene acceptor materials in organic optoelectronic device [4-6]. Based on the non-fullerene material ITIC, an outstanding power conversion efficiencies (PCEs) higher than 11% was achieved by S. Li in the organic photovoltaic (OPV) [7]. Zhan and co-workers had reported organic photo detector (OPD) with a high detectivity (D*) of 10 12 Jones at ±15V, because the band bending decreases the tunneling-injection barriers of the oppositely charged carriers under light illumination [8]. However, the OPD based on photovoltaic effect using the PBDB-T : ITIC active layer has not been reported. In this work, we fabricated organic optoelectronic devices with photovoltaic and detective performance based on the active layer of PBDB-T:ITIC. Also, the NPB and TPD were employed as hole transport layers (HTL) to improve the PCE of OPV and reduce the dark current of OPD. Experimental The molecular structures of ITIC, PBDB-T, TPD and NPB are shown in Fig. 1(a), and the schematic device structure is indium tin oxide (ITO)/ZnO (40 nm)/PBDB-T:ITIC (100 nm)/HTL (10 nm)/ MoO3 (15 nm) /Ag (100 nm) as depicted in Fig. 1(b). The ITO-coated glass substrates with a 10 Ω/sq sheet resistance were cleaned successively in an ultrasonic bath containing detergent, acetone, deionized water, and isopropyl alcohol each step for 15 min, and dried in an oven for 2h at 3rd Annual International Conference on Advanced Material Engineering (AME 2017) Copyright

Estimation of exciton reverse transfer for variable spectra and high efficiency in interlayer-based organic light-emitting devices

Organic light-emitting devices (OLEDs) with three different exciton adjusting interlayers (EALs), which are inserted between two complementary blue and yellow emitting layers, are fabricated to demonstrate the relationship between the EAL and device performance. The results show that the variations of type and thickness of EAL have different adjusting capability and distribution control on excitons. However, we also find that the reverse Dexter transfer of triplet exciton from the light-emitting layer to the EAL is an energy loss path, which detrimentally affects electroluminescent (EL) spectral performance and device efficiency in different EAL-based devices. Based on exciton distribution and integration, an estimation of exciton reverse transfer is developed through a triplet energy level barrier to simulate the exciton behavior. Meanwhile, the estimation results also demonstrate the relationship between the EAL and device efficiency by a parameter of exciton reverse transfer probability. The estimation of exciton reverse transfer discloses a crucial role of the EALs in the interlayer-based OLEDs to achieve variable EL spectra and high efficiency.