June 2014 - August 2014
Publisher: Chairman Gong-Ru Lin  Editors: Professor Chao-Hsin Wu, Ms. Hsiao-wen Lin  October 30, 2014

Congratulations to Professor Chi-Kuang Sun, GIPO, on his being elected the Y. Z. Hsu Scientific Award’s 12th scientific chair professor!

Award Category Name

Y. Z. Hsu Scientific Award,12th Scientific Chair Professor

Optoelectronics Technology Professor Chi-Kuang Sun

Congratulations to Professor Ching-Fuh Lin, GIPO, on his being awarded the Y. Z. Hsu Scientific Award’s 6th technology invention award!

Award Invention patent Name

Y. Z. Hsu Scientific Award, 6th Technology Invention Award

Mixed-typed heterojunction thin-film solar cell structure and method for fabrication the same

Professor Ching-Fuh Lin

Congratulations to Professor Gong-Ru Lin, GIPO, on his paper, “All-optical modulation based on silicon quantum dot doped SiOx:Si-QD waveguide”, being published on the journal “Laser and Photonics Review”! For more information, please refer to the following NTU website: http://host.cc.ntu.edu.tw/sec/schinfo/schinfo_asp/ShowContent.asp?num=1180&sn=12524

Congratulations to Tsung-Jui Yang, a GIPO graduate student, on his being awarded, under the instruction of GIPO professor Yuh-Renn Wu, the “2014 ISNE Best Student Paper Award (oral presentation)”!



May “GIPO Colloquium” Highlights (Compiled by Li-Chi Yao)


3:30 pm, May 2 (Fri.), 2014
Speaker: Dr. Rick Shen (President, eMemory Technology Inc.)
Topic: From technology exploitation to it being given authorization to industries

President Rick Shen visited GIPO on May 2nd (Fri.) and delivered the speech “From technology exploitation to it being given authorization to industries” at lecture theater 101, Barry Lam Hall. His speech was fascinating and content-rich, and the professor interacted well with students. GIPO teachers and students participated in this event with enthusiasm and benefited greatly.


President Rick Shen (right), and the host of the speech, Professor Way-Seen Wang (left)



3:30 pm, May 9 (Fri.), 2014
Speaker: Kenneth Tai (Chairman, InveStar Corporation)
Topic: Blue Ocean Strategy

InveStar Chairman Kenneth Tai visited GIPO on May 9th (Fri.) and delivered a speech concerning “Blue Ocean Strategy” at lecture theater 101, Barry Lam Hall. His speech was excellent, and the professor interacted well with his audience. GIPO teachers and students participated enthusiastically and learned a great deal.


Chairman Kenneth Tai (right), and GIPO chairman, Professor Gong-Ru Lin (left)



3:30 pm, May 16 (Fri.), 2014
Speaker: Professor Daw-Wei Wang (Department of Physics, National Tsing Hua University)
Topic: Taiwanese youths’ future predicaments and challenges

Professor Daw-Wei Wang visited GIPO on May 16th (Fri.) and delivered a speech concerning “Taiwanese youths’ future predicaments and challenges” at lecture theater 105, EE-Ⅱ Building. His speech was fascinating, and the professor interacted well with students. GIPO teachers and students attended the speech with enthusiasm and learned a great deal.


Professor Daw-Wei Wang (left), and the host of this speech, Professor Way-Seen Wang (right)



3:30 pm, May 23 (Fri.), 2014
Speaker: Ming-Zen Chien (Chairman, First Financial Assets Management Co., Ltd.)
Topic: Practical ways of financing new businesses

Chairman Ming-Zen Chien visited GIPO on May 23rd (Fri.) and delivered a speech concerning “Practical ways of financing new businesses” at lecture theater 101, Barry Lam Hall. His speech was fascinating and covered a wide-range of issues, and the chairman interacted well with students. GIPO teachers and students found the event to be an interesting and educational experience.


Chairman Ming-Zen Chien (left), and the host of this speech, Professor Way-Seen Wang (right)



3:30 pm, May 30 (Fri.), 2014
Speaker: Chun-Ting Liu (General Director, Electronics and Optoelectronics Research Laboratories, Industrial Technology Research Institute of Taiwan, R.O.C.)
Topic: The prospective development trend of electronics and optoelectronics’ industries
  General Director Chun-Ting Liu visited GIPO on May 30 (Fri.) and delivered a speech concerning “The prospective development trend of electronics and optoelectronics’ industries” at lecture theater 105, EE-Ⅱ Building. His speech was fascinating, and the speaker interacted well with students. GIPO teachers and students learned a great deal for the event.



~ Sidelights on the GIPO Cup sports games, 2014 ~

(Time: May 4, 2014;Location: NTU Gymnasium)

Composed by Ting-Hao Chen, the President of GIPO Student Association

The 2014 GIPO Cup sports games took place on a sunny Sunday afternoon at NTU Gymnasium. There were 3 types of games this year, which were the 3-vs-3 street basketball, the magic free-throw, and the badminton tournament respectively. In order to give participants some sort of surprise, the organizer had refused to divulge anything about the details of the magic free-throw to anyone, regardless of constant inquiries. In addition to grand prizes for all the top 3 winners, there are also trophies this year, and so the number of students registered for these games was extremely high.

3-vs-3 street basketball was the first event to take place. There were 14 teams registered for the game this year, which was played according to elimination rules. To win the shiny and glorious cup, every young player gave it his/her all on the basketball court. Even when the contestants were knocked down, they stood up immediately; their fighting bravery was worth great admiration.


The top 3 teams in 3-vs-3 street basketball:
The champion: Liang Liao, Yen-An Chen, Wei-Chih Hsu, Po-Han Fu
The 1st runner-up: Yin-Jie Huang, Gong-Sheng Cheng, Sin-Yi Yin, Li-Cheng Chang
The 2nd runner-up: Ming-Chun Lee, Charng-Gan Tu, Danny Weng, Chun-Han Lin

The next was the magic free-throw. Different from other regular free-throws, which only involve basketballs, this one includes basketballs, volleyballs, soccer balls, shuttlecocks, and tennis balls, for a total of 5 different kinds of balls. Each player threw 3 of each of the 5 kinds of balls, i.e. 15 balls altogether, and the one who threw in the most would win. I also participated in this game, but, unfortunately, threw in merely 4 balls, a number which was far from winning any prize. And, it was really impressive that someone could throw in over 10 balls.


The top 3 players in the magic free-throw:
The champion: Li-Tien Wei
The 1st runner-up: Sin-Yi Yin
The 2nd runner-up: Wei-Fu Chang

The last was the badminton tournament, which was divided into singles and doubles. The game was also played with strict elimination rules, with 7 contestants competing for the singles and 6 teams competing for the doubles. With every player striving to win the prize, there were constant shouts of surprise and support from courtside, and the entire gym was filled with excitement.


The top 3 players in the badminton tournament singles:
The champion: Li-Tien Wei
The 1st runner-up: Cheng-Chieh Lee
The 2nd runner-up: Jeng-Gang Tsai
The top 3 teams in the badminton tournament doubles:
The champion: Meng-Yu Weng, Chien-Ming Lee
The 1st runner-up: Cian-Yi Hong, Po-Han Fu
The 2nd runner-up: Wei-Hsuan Tseng, Jung-Hung Chang

 After the badminton tournament, the 2014 GIPO Cup sports games officially came to a successful close. We would like to thank GIPO teachers and office staff for your encouragement and kind support, and thanks also to participating contestants and all those who came to cheer for the games. We hope these games gave everyone a chance to stretch their limbs, and improved friendships among laboratories. Finally, we would also like to thank our Student Association buddies. It’s so wonderful to have you!




~ Sidelights on the 2014 GIPO undergraduates’ optoelectronics summer camp ~

(Time: August 5-7, 2014;Location: Barry Lam Hall, NTU)

Composed by Ting-Hao Chen, the President of GIPO Student Association

The 2014 NTU optoelectronics summer camp has come on the stage under the brilliant sun in August!

Are you feeling confused about which graduate institute you should attend, what optoelectronics graduate institutes are doing, or how optoelectronics graduates would find jobs in the future? The 2014 NTU optoelectronics summer camp has all the answers for you! In order to let undergraduates know more about optoelectronics and its industry prospects so students can make the right decisions in choosing graduate schools, we have especially organized this 3-day-camp. Participants can find answers to the above questions in lectures, visits and interacting with GIPO students. This year we have undergraduates from many universities, most students majoring in electronics engineering or physics-related subjects, participating in the camp.

The 1st day’s 1st session was Chairman Gong-Ru Lin’s brief introduction to optoelectronics. Next was an interaction session. Participants and GIPO students were divided into 4 groups to discuss the above-mentioned questions face to face. We discovered that participants were more interested in appraisals of applications for graduate schools than anything else. Next was Prof. Hoang-Yan Lin’s lecture on the technology and industry of solid-state lighting. In the afternoon, we had Prof. Chih-I Wu giving us an introduction to light-emitting diode. Next were the laboratory visits and hands-on experiment sessions. Participants got to know how laboratories work by visiting them and also understood a little more about optoelectronics experiments through completing the work.


Students probably felt that the 2nd day was the most fun, because we went on a field trip, visiting Lite-On Technology Corp. and National Applied Research Laboratories’ Instrument Technology Research Center; the latter is Taiwan’s important instrument research organization which develops instrument technology in accordance with our country’s technology policies. In the morning, we visited Lite-on Technology Corp., a big manufacturer of optoelectronics modules. And, in the afternoon, we visited Instrument Technology Research Center in Hsinchu.

The 3rd day’s 1st session was a special secret activity. We provided an entertaining program “super bi-i-bi” for participants to stretch their limbs. Students were inspired to strive to their utmost, in order to win the exquisite gift especially provided by GIPO. Next, Prof. Hoang-Yan Lin, who delivered the technology and industry of solid-state lighting on the 1st day, delivered an introduction to display technology and industry. Next, Prof. Chao-Hsin Wu delivered a speech on the technology of solar cells. And, the popular Prof. Chi-Kuang Sun delivered the introduction of biophotonics technology. It appeared that Prof. Chi-Kuang Sun was very popular among students since they followed him, asking questions even when the session was over.


For our finale, we organized another entertaining program “draw & guess” as our ending session. This program demanded both drawing and guessing capabilities. Each team sent one member on stage to draw a picture concerning a specific topic designated by the organizer, and the rest of the team had to guess what the member is drawing. During the game, the whole conference room was filled with bursts of laughter and boos from time to time. Obviously, it really challenged our guessing capabilities, and we really enjoyed it.

After the last entertaining program, the GIPO Chairman Lin delivered a concluding report and conferred certificates to students. Afterward, we had an afternoon-tea party and everyone was pleasantly surprised by the great bounty of food. The winner of the “draw & guess” game was the 1st team; I was very impressed with their amazing guessing abilities. Congratulations to the 1st team; they really deserved the 1st prize. Finally, this camp came to an end after students exchanged personal information and took a group photo. We appreciated your participation in this camp very much, and look forward to see you again next year!




 2014 International Conference on Trend, Challenges, and Opportunities in Nano Energy

(Time: May 13, 2014;Location: Barry Lam Hall, NTU)

Composed by Hui-Chun Fu

The 2014 International Conference on Trend, Challenges, and Opportunities in Nano Energy, organized by Professor Jr-Hau He, GIPO, NTU, drew to a successful close on May 13th. This conference aggregated top scholars and engineers worldwide, including material scientists, electronics engineers, and physics scholars. It depicted the world’s future nanoenergy-technology cross-field stage, and furnished the academia-industry with a professional, multi-functional interflow platform. Through this conference, we put the most advanced technology forward to the market faster than ever before. Anyone interested in this technology, whether they are students, industrial technicians, or even investors, could use the event to create opportunities for many people, and provide great benefit for the research and development of academia and industry.

We were greatly honored to have Professor Chennupati Jagadish (Deputy Dean and Academician of Australian Research School of Sciences), Professor Paul Yu (ex-Vice President of University of California, San Diego, President of IEEE Electron Device Society), and all other excellent academic leaders with us today to share these advanced research results. Through panel sessions, we met together to discuss the world’s hottest and most advanced subjects, to inspire more creative research ideas, and to expand interactions between fields and countries. We believe that interaction with the world’s top academicians would help us greatly in broadening our horizons, researching newer technologies, and enhancing our related knowledge. Of course, it could also inspire further ideas among nanoenergy industries, and provide young optoelectronic scientists with more knowledge and work interaction opportunities.

We would herewith like to thank EECS, GIPO, and the Office of Research and Development, NTU, for your kind assistance in preparations for this conference and for enabling it to be held successfully.

From left to right, Professor Jr-Hau He, Professor Gong-Ru Lin, Professor Ray-Hua Horng, Professor Paul Yu, Professor Jagadish, Professor Ching-Ting Lee, Professor Hao-Chung Kuo, and Professor Jian-Jang Huang

A group photo of all attending scholars, taken in front of Barry Lam Hall


~ A visit to InnoLux Display Corporation ~

(Time: August 1, 2014)

Composed by Tzu-Yu Chen

Participants: Chairman Gong-Ru Lin, Prof. Hung-Chun Chang, Prof. Ching-Fuh Lin, Prof. Chieh-Hsiung Kuan, Prof. Hoang-Yan Lin, Prof. Chih-I Wu, Prof. Yih-Peng Chiou, Prof. Guo-Dung Su, and Prof. Wing-Kit Choi

We recently visited InnoLux Display Corporation’s TOC factory in Southern Taiwan Science Park, Tainan. InnoLux was one of Taiwan’s most important panel manufacturers, which possessed all-inclusive continuous production lines of all sizes of LCD panel and touchscreens. By virtue of its creative research techniques, InnoLux had sold tons of advanced panels and related products to countries around the world. Our visiting schedule was arranged by Jen-Yung Chang, InnoLux manager, and we were received by Wen-Chih Sa, vice president, himself. We had visited the continuous production line of touchscreens and the demo room of panel and related products. Afterwards, InnoLux’s research team and GIPO professors met to talk about the basic plans for future research cooperation, student scholarships, and academia-industry cooperation. After the meeting, this visit came to its successful conclusion. We anticipate that, through this visit, GIPO’s research cooperation with InnoLux can be firmly established and our research capability can also be effectively promoted.

A group photo of GIPO professors, taken at InnoLux’s factory


Graphene to substrate energy transfer through out-of-plane longitudinal acoustic phonons

Professor Chi-Kuang Sun

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

Graphene is often deposited on substrates for practical purposes. The graphene-substrate interactions have been the focus of many discussions because they induce property modifications and result in considerable energy transfer at the interface. However, the proposed mechanisms were restricted to the 2D plane and interface, while the energy conduction in the third dimension is hardly considered. Herein, we applied nano-ultrasonic spectroscopy with a piezoelectric nano-layer embedded in the substrate to study the energy transfer perpendicular to the interface of the combined system of the 2D graphene and the 3D base. The result revealed energy dissipation of optically excited graphene via emitting out-of-plane longitudinal acoustic phonon into the substrate. We found that, under photo-excitation by a femtosecond laser pulse, graphene can emit longitudinal coherent acoustic phonons (CAPs) with frequency bandwidth over 1 THz into the substrate. In addition, the waveform of the CAP pulse infers that the photo-carriers and sudden lattice heating in graphene caused modification of graphene-substrate bond and consequently generated longitudinal acoustic phonons in the substrate. The direct observation of this unexplored graphene to substrate vertical energy transfer channel brings new insights into the understanding of the energy dissipation and limited transport properties of supported graphene.

Fig. (Left)The schematic of applying femtosecond laser pulses to study energy transfer at the interface of graphene and substrate. (Right) The experimental data of differential transient transmission (T/T) that reveals the generation of out-of-plane longitudinal acoustic phonon in the substrate by the exclusively photo-excited graphene.

Reference: I-Ju Chen, Pierre-Adrien Mante, Cheng-Kai Chang, Szu-Chi Yang, Hui-Yuan Chen, Yu-Ru Huang, Li-Chyong Chen, Kuei-Hsien Chen, Vitalyi Gusev, and Chi-Kuang Sun, “Graphene-to-substrate energy transfer through out-of-plane longitudinal acoustic phonons,” Nano Letters, 1317−1323, 14, 2014


Investigation of designated eye position and viewing zone for a two-view autostereoscopic display

Professor Hoang-Yan Lin

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

Designated eye position (DEP) and viewing zone (VZ) are important optical parameters for designing a two-view autostereoscopic display (Figs. 1 and 2). Although much research has been done to date, little empirical evidence has been found to establish a direct relationship between design and measurement. More rigorous studies and verifications to investigate DEP and to ascertain the VZ criterion will be valuable. We propose evaluation metrics based on equivalent luminance (EL) and binocular luminance (BL) to figure out DEP and VZ for a two-view autostereoscopic display. Simulation and experimental results (Fig. 3) prove that our proposed evaluation metrics can be used to find the DEP and VZ accurately. (Optics Express, Vol. 22, Issue 4, pp.4751-4767, 2014.)

Fig. 1. Schematic diagram for a two-view autostereoscopic display design. The figure is for illustration and not to the scale. In practice, Z>>f and PE >>PD.

Fig. 2. The VZ defined by geometric line plot from side sub-pixels. The figure is for illustration and not to the scale. In practice, Z is much greater than f and PE is much greater than PD.

Fig. 3. Experiment for verifying the reconstruction map based on equivalent luminance. Calcuated peak LReq at the first lobe (+1) is at (x, y, z)= (17.5~17.75, 0, 103~104.5). The observed pictures for (a) a B/W pattern and (b) natural picture are shown at the observation point (17.5, 0, 103) marked at (c). Those for (d) a B/W pattern and (e) natural picture are shown at the observation point (15.5, 0, 103) marked at (f).


Si and SiC quantum dots co-doped Si-rich SiC p-i-n junction diode with enhanced blue-green light emission

Professor Gong-Ru Lin's Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

Si quantum dots (Si-QDs) and SiC quantum dots (SiC-QDs) co-doped Si-rich silicon carbide (SixC1-x) based p-i-n junction light-emitting diodes (LEDs) with blue-green light emission is demonstrated. By growing the SixC1-x with plasma-enhanced chemical vapor deposition (PECVD) at relatively low temperature, the turn-on voltage of Si-rich SixC1-x LEDs can be reduced to 6.1 V when thinning i-SixC1-x layer to 25 nm because of higher tunneling probability and lower series resistance. The electroluminescent (EL) power increases to 136 nW, however, which inversely attenuates due to the reduced SiC-QDs if the i-SixC1-x thickness further shrinks to 25 nm. The principle EL peak at 500 nm with narrower shape and blue-green emission pattern is attributed to the self-trapped excitons at surface states among SiC-QDs. The external quantum efficiency (EQE) of the Si-rich SixC1-x LEDs with i-SixC1-x thickness of 50 nm is up to 1.58×10-1% with enhanced carrier tunneling probability. The carrier injection efficiency is enhanced to 46% by increasing the doping concentration to 1016 cm-3, leading to almost one order of magnitude improvement on the EQE of Si-rich SixC1-x LEDs.


Left: The TEM images (Upper) of the Si-rich SixC1-x films (Left) with co-doped SiC-QDs and Si-QDs in average sizes of 2.5 nm and 4.3 nm, respectively with the size distribution (Lower) of SiC-QDs and Si-QDs in the Si-rich SixC1-x film with the thickness of 50 nm.

Middle: The I-V (Lower) and P-I (Upper) characteristics of the Si-rich SixC1-x p-i-n junction LEDs with different i-SiC thickness grown with the fluence ratio of 60%.

Right: The EL spectra (Upper) of Si-rich SixC1-x p-i-n junction LEDs with the different i-SixC1-x thickness.

Inset: the EL emission pattern. The carrier injection efficiency (Lower) of the Si-rich SixC1-x p-i-n junction LED as a function of n-type dopant concentration under fixed B2H6 doping concentration.

Reference: Hung-Yu Tai, Chih-Hsien Cheng, and Gong-Ru Lin, “Blue-Green Light Emission from Si and SiC quantum dots co-doped Si-rich SiC p-i-n Junction Diode,” IEEE J. Sel. Top. Quantum Electron., Vol. 20, Issue 4, 8200507, Jul.-Aug. 2014.


ITO-free low-index transparent electrodes for enhancing light out-coupling of organic light-emitting devices

Professor Chung-Chih Wu

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

The transparent conductor indium tin oxide (ITO) has been widely used in organic light-emitting devices (OLEDs) and other organic/inorganic optoelectronics as the transparent electrode. ITO, however, is rather expensive and thus not cost-effective due to scarcity of the indium element on earth. ITO is also brittle and usually requires high-temperature processing, limiting its compatibility with flexible plastic substrates and thus its use for flexible devices. Accordingly, in recent years, alternative (ITO-free) transparent conductors/electrodes for replacement of ITO are being intensively pursued. Through our studies, we have developed high-conductivity conducting polymers having excellent mechanical flexibility, good transmittance, solution processing capability, and low cost. Most importantly, they possess high conductivity of up to ~1000 S/cm, similar to that conventional ITO and sufficient to replace ITO as alternative transparent electrodes in various optoelectronic devices. Intriguingly, such high-conductivity conducting polymers also possess an optical refractive index significantly lower than those of ITO and typical organic layers in OLEDs and well matching those of typical OLED substrates. Optical simulation reveals that by replacing ITO with such a low-index transparent electrode, the guided modes trapped within the organic/ITO layers in conventional OLEDs can be substantially suppressed, leading to more light coupled into the substrate than the conventional ITO device (Fig. 1). By applying light out-coupling structures onto outer surfaces of substrates to effectively extract radiation into substrates, OLEDs using such low-index transparent electrodes achieve much enhanced optical out-coupling and electroluminescence efficiencies (EQE up to 45%, luminous efficiency up to185 lm/W) in comparison with conventional OLEDs using ITO (Fig. 2).

Fig. 1. Calculated mode distributions (fraction of radiation coupled into different modes) of OLED internally generated radiation

Fig. 2. External quantum efficiencies and luminous efficiencies of various devices


Role of Cathode Connecting Layers and Energetic Alignment in Organic Photovoltaic Devices

Professor Chih-I Wu

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

Open-circuit voltage is one of the key parameters affecting the performance of organic photovoltaic devices. Several electronic mechanisms originating from energy band alignment within the path of charge transport and carrier extraction are the major factors that limit the Voc. We demonstrated that the influence of energetic disorder due to introduced cathode buffer layers between active layer and metal cathode can contribute to energetic favorable charge transport and extraction, leading to Voc enhancement. To explore the dependence of Voc on the energetic properties of the contacting materials prior to cathode deposition, we proposed a comprehensive model for buffer layers based on molecular materials commonly employed in OLED and OPV cells.

Energy band alignment of various cathode buffer layers in P3HT/PCBM based bulk-heterojunction (BHJ) solar cell are checked via in situ ultra-violet photoemission spectroscopy (UPS) and the results are organized as follows: First, we clarified the correlation between charge transport property and carrier extraction ability at buffer layers with energetic favorable band alignment. This includes a presentation of qualitative models for the dependence of HOMO and LUMO offset between active layer and buffer layer on the shunt resistance and series resistance, and short-circuit current density, or saturated value of Voc based on Shockley’s theory for p-n junctions. Second, the dependence of Voc and OPV operating parameters on the cathode contacting materials with inappropriate energy offset or transport ability, such as narrow band gap and hole transport materials, were obtained. We investigated not only the LUMO offset related to electron transport, but also the influence of HOMO offset on carrier extraction at cathode contact. Experimental details and device performance are provided in our recent publication. As a result, the performance of P3HT/PCBM based BHJ solar cells with various buffer materials can be classified into three class according to the energy offset. Class I contained large HOMO and LUMO offset so the better hole blocking and electron transport ability lead to a saturated value, 0.6 V, of Voc in P3HT/PCBM system. Class II has either large HOMO offset or LUMO offset making a small decrease in Voc and a poor Voc for Class III due to inappropriate energy offset of buffer materials. Finally, we summarize the key findings to propose and verify a new model which gives predictions for the maximum Voc in BHJ solar cells consisting of buffer materials.


Organic solar cell with 95.6% internal quantum efficiency

Professor Jiun-Haw Lee

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

With suitable device and fabrication design, an organic solar cell (OSC) with 95.6% internal quantum efficiency (IQE) was demonstrated with boron subphthalocyanine chloride (SubPc) and C60 as the electron donor and acceptor materials, respectively. To improve the open circuit voltage (VOC), SubPc/C60 heterojunction structure was employed. Suitable deposition rate of SubPc was needed between the tradeoff between VOC and fill factor. 3-nm N,N-dicarbazolyl-3,5-benzene (mCP) was inserted between indium-tin-oxide (ITO) anode and SubPc which served as the exciton and electron blocking layer. Combined with layer thickness optimization, IQE of such an OSC reached 95.6% at the absorption peak 590 nm.

Fig.1. (a) J–V characteristics and (b) IQE of OSC with different mCP thickness



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