Works by Ko, Seo‐Jin

Results: 34

Dithieno[3,2- b:2′,3′- d]pyrrole and Benzothiadiazole-Based Semicrystalline Copolymer for Photovoltaic Devices with Indene-C60 Bisadduct.

Published in:

Macromolecular Chemistry & Physics, 2013, v. 214, n. 18, p. 2083, doi. 10.1002/macp.201300303

By:

Lee, Wonho;
Kim, Gi‐Hwan;
Jeong, Eunjae;
Wang, Xiaowei;
Yum, Seungjib;
Ko, Seo‐Jin;
Hwang, Sungu;
Kim, Jin Young;
Woo, Han Young

Publication type:

Article

Photocurrent Extraction Efficiency near Unity in a Thick Polymer Bulk Heterojunction.

Published in:

Advanced Functional Materials, 2016, v. 26, n. 19, p. 3324, doi. 10.1002/adfm.201505556

By:

Ko, Seo‐Jin;
Walker, Bright;
Nguyen, Thanh Luan;
Choi, Hyosung;
Seifter, Jason;
Uddin, Mohammad Afsar;
Kim, Taehyo;
Kim, Seongbeom;
Heo, Jungwoo;
Kim, Gi‐Hwan;
Cho, Shinuk;
Heeger, Alan J.;
Woo, Han Young;
Kim, Jin Young

Publication type:

Article

New 3,8‐difluoro indoloindole‐based copolymers for organic solar cell.

Published in:

International Journal of Energy Research, 2021, v. 45, n. 5, p. 7806, doi. 10.1002/er.6365

By:

Lee, Gyeong Seok;
Shin, Hee Jeong;
Shome, Sanchari;
Park, Ji‐Hyun;
Ko, Seo‐Jin;
Choi, Hyosung;
Kim, Yun‐Hi

Publication type:

Article

Achieving Highly Sensitive Near‐Infrared Organic Photodetectors using Asymmetric Non‐Fullerene Acceptor.

Published in:

Advanced Optical Materials, 2023, v. 11, n. 17, p. 1, doi. 10.1002/adom.202300312

By:

Lee, Un‐Hak;
Park, Byoungwook;
Rhee, Seunghyun;
Ha, Jong‐Woon;
Whang, Dong Ryeol;
Eun, Hyeong Ju;
Kim, Jong H.;
Shim, Yeongseok;
Heo, Junseok;
Lee, Changjin;
Kim, Bumjoon J.;
Yoon, Sung Cheol;
Lee, Jaewon;
Ko, Seo‐Jin

Publication type:

Article

Crystallization‐Driven Optimization of Morphology and Performance in Near‐Infrared Organic Photodetectors via Alkyl Side Chain Tuning of Narrow Bandgap Non‐Fullerene Acceptors.

Published in:

Advanced Functional Materials, 2024, v. 34, n. 34, p. 1, doi. 10.1002/adfm.202400676

By:

Cho, Kyounguk;
Ha, Jong‐Woon;
Nam, Minwoo;
Lee, Chihyung;
You, Seung Ju;
Lee, Ah Young;
Yoon, Sung Cheol;
Han, Mijeong;
Kim, Jong H.;
Ko, Seo‐Jin;
Ko, Doo‐Hyun

Publication type:

Article

Low Voltage‐Loss Organic Solar Cells Light the Way for Efficient Semitransparent Photovoltaics.

Published in:

Solar RRL, 2022, v. 6, n. 8, p. 1, doi. 10.1002/solr.202200135

By:

Luginbuhl, Benjamin R.;
Ko, Seo-Jin;
Ran, Niva A.;
Hu, Huawei;
Becwar, Shona M.;
Karki, Akchheta;
Seifrid, Martin;
Okubo, Takashi;
Wang, Ming;
Ade, Harald W.;
Chmelka, Bradley F.;
Bazan, Guillermo C.;
Manjunatha Reddy, G. N.;
Nguyen, Thuc-Quyen

Publication type:

Article

Organic X‐Ray Image Sensors Using a Medium Bandgap Polymer Donor with Low Dark Current.

Published in:

Energy & Environmental Materials, 2024, v. 7, n. 6, p. 1, doi. 10.1002/eem2.12750

By:

Ha, Jong‐Woon;
Eom, Seung Hun;
Cha, Bo Kyung;
Song, Seyeong;
Eun, Hyeong Ju;
Kim, Jong H.;
Park, Jong Mok;
Kim, BongSoo;
Park, Byoungwook;
Ko, Seo‐Jin;
Yoon, Sung Cheol;
Lee, Changjin;
Jung, In Hwan;
Hwang, Do‐Hoon

Publication type:

Article

Versatile surface plasmon resonance of carbon-dot-supported silver nanoparticles in polymer optoelectronic devices.

Published in:

Nature Photonics, 2013, v. 7, n. 9, p. 732, doi. 10.1038/nphoton.2013.181

By:

Choi, Hyosung;
Ko, Seo-Jin;
Choi, Yuri;
Joo, Piljae;
Kim, Taehyo;
Lee, Bo Ram;
Jung, Jae-Woo;
Choi, Hee Joo;
Cha, Myoungsik;
Jeong, Jong-Ryul;
Hwang, In-Wook;
Song, Myoung Hoon;
Kim, Byeong-Su;
Kim, Jin Young

Publication type:

Article

Effect of Cyano Substitution on Non‐Fullerene Acceptor for Near‐Infrared Organic Photodetectors above 1000 nm (Adv. Funct. Mater. 8/2023).

Published in:

Advanced Functional Materials, 2023, v. 33, n. 8, p. 1, doi. 10.1002/adfm.202370042

By:

Ha, Jong‐Woon;
Eun, Hyeong Ju;
Park, Byoungwook;
Ahn, Hyungju;
Hwang, Dong Ryeol;
Shim, Yeong Seok;
Heo, Junseok;
Lee, Changjin;
Yoon, Sung Cheol;
Kim, Jong H.;
Ko, Seo‐Jin

Publication type:

Article

Effect of Cyano Substitution on Non‐Fullerene Acceptor for Near‐Infrared Organic Photodetectors above 1000 nm.

Published in:

Advanced Functional Materials, 2023, v. 33, n. 8, p. 1, doi. 10.1002/adfm.202211486

By:

Ha, Jong‐Woon;
Eun, Hyeong Ju;
Park, Byoungwook;
Ahn, Hyungju;
Hwang, Dong Ryeol;
Shim, Yeong Seok;
Heo, Junseok;
Lee, Changjin;
Yoon, Sung Cheol;
Kim, Jong H.;
Ko, Seo‐Jin

Publication type:

Article

Significant Dark Current Suppression in Organic Photodetectors Using Side Chain Fluorination of Conjugated Polymer (Adv. Funct. Mater. 4/2022).

Published in:

Advanced Functional Materials, 2022, v. 32, n. 4, p. 1, doi. 10.1002/adfm.202270025

By:

Park, Byoungwook;
Jung, Juhyoung;
Lim, Dae‐Hee;
Lee, Hanbee;
Park, Sungjun;
Kyeong, Minju;
Ko, Seo‐Jin;
Eom, Seung Hun;
Lee, Seung‐Hoon;
Lee, Changjin;
Yoon, Sung Cheol

Publication type:

Article

Significant Dark Current Suppression in Organic Photodetectors Using Side Chain Fluorination of Conjugated Polymer.

Published in:

Advanced Functional Materials, 2022, v. 32, n. 4, p. 1, doi. 10.1002/adfm.202108026

By:

Park, Byoungwook;
Jung, Juhyoung;
Lim, Dae‐Hee;
Lee, Hanbee;
Park, Sungjun;
Kyeong, Minju;
Ko, Seo‐Jin;
Eom, Seung Hun;
Lee, Seung‐Hoon;
Lee, Changjin;
Yoon, Sung Cheol

Publication type:

Article

Conjugated Polymers: Exploring Wholly Doped Conjugated Polymer Films Based on Hybrid Doping: Strategic Approach for Optimizing Electrical Conductivity and Related Thermoelectric Properties (Adv. Funct. Mater. 42/2020).

Published in:

Advanced Functional Materials, 2020, v. 30, n. 42, p. 1, doi. 10.1002/adfm.202070276

By:

Yoon, Sang Eun;
Kang, Yeongkwon;
Jeon, Gyeong G.;
Jeon, Dohyeon;
Lee, Sang Yeon;
Ko, Seo‐Jin;
Kim, Taekyeong;
Seo, Hyungtak;
Kim, Bong‐Gi;
Kim, Jong H.

Publication type:

Article

Exploring Wholly Doped Conjugated Polymer Films Based on Hybrid Doping: Strategic Approach for Optimizing Electrical Conductivity and Related Thermoelectric Properties.

Published in:

Advanced Functional Materials, 2020, v. 30, n. 42, p. 1, doi. 10.1002/adfm.202004598

By:

Yoon, Sang Eun;
Kang, Yeongkwon;
Jeon, Gyeong G.;
Jeon, Dohyeon;
Lee, Sang Yeon;
Ko, Seo‐Jin;
Kim, Taekyeong;
Seo, Hyungtak;
Kim, Bong‐Gi;
Kim, Jong H.

Publication type:

Article

Synthesis of the Copolymer Based on Diketopyrrolopyrrole with Didecyl Chain for OPVs.

Published in:

Molecular Crystals & Liquid Crystals, 2014, v. 600, n. 1, p. 88, doi. 10.1080/15421406.2014.936791

By:

Song, Suhee;
Ko, Seo-Jin;
Kim, Taehyo;
Shin, Hyunmin;
Kim, Il;
Kim, Jin Young;
Suh, Hongsuk

Publication type:

Article

Structurally Driven Ultrafast Charge Funneling in Organic Bulk Heterojunction Hole Transport Layer for Efficient Colloidal Quantum Dot Photovoltaics (Adv. Energy Mater. 20/2023).

Published in:

Advanced Energy Materials, 2023, v. 13, n. 20, p. 1, doi. 10.1002/aenm.202370081

By:

Yang, Jonghee;
Sharma, Ashish;
Yoon, Jung Won;
Paritmongkol, Watcharaphol;
Lee, Seungjin;
Ahn, Hyungju;
Lee, Wooseop;
Song, Hochan;
Jeong, Woo Hyeon;
Lee, Bo Ram;
Ko, Seo‐Jin;
Ahmadi, Mahshid;
Sargent, Edward H.;
Choi, Hyosung

Publication type:

Article

Structurally Driven Ultrafast Charge Funneling in Organic Bulk Heterojunction Hole Transport Layer for Efficient Colloidal Quantum Dot Photovoltaics.

Published in:

Advanced Energy Materials, 2023, v. 13, n. 20, p. 1, doi. 10.1002/aenm.202203749

By:

Yang, Jonghee;
Sharma, Ashish;
Yoon, Jung Won;
Paritmongkol, Watcharaphol;
Lee, Seungjin;
Ahn, Hyungju;
Lee, Wooseop;
Song, Hochan;
Jeong, Woo Hyeon;
Lee, Bo Ram;
Ko, Seo‐Jin;
Ahmadi, Mahshid;
Sargent, Edward H.;
Choi, Hyosung

Publication type:

Article

Rational Design of Highly Efficient Semi‐Transparent Organic Photovoltaics with Silver Nanowire Top Electrode via 3D Optical Simulation Study.

Published in:

Advanced Energy Materials, 2021, v. 11, n. 47, p. 1, doi. 10.1002/aenm.202102397

By:

Jeong, Hong In;
Biswas, Swarup;
Yoon, Sung Cheol;
Ko, Seo‐Jin;
Kim, Hyeok;
Choi, Hyosung

Publication type:

Article

Temperature and Light Modulated Open‐Circuit Voltage in Nonfullerene Organic Solar Cells with Different Effective Bandgaps.

Published in:

Advanced Energy Materials, 2021, v. 11, n. 4, p. 1, doi. 10.1002/aenm.202003091

By:

Brus, Viktor V.;
Schopp, Nora;
Ko, Seo‐Jin;
Vollbrecht, Joachim;
Lee, Jaewon;
Karki, Akchheta;
Bazan, Guillermo C.;
Nguyen, Thuc‐Quyen

Publication type:

Article

Quantifying the Nongeminate Recombination Dynamics in Nonfullerene Bulk Heterojunction Organic Solar Cells.

Published in:

Advanced Energy Materials, 2019, v. 9, n. 32, p. N.PAG, doi. 10.1002/aenm.201901438

By:

Vollbrecht, Joachim;
Brus, Viktor V.;
Ko, Seo‐Jin;
Lee, Jaewon;
Karki, Akchheta;
Cao, David Xi;
Cho, Kilwon;
Bazan, Guillermo C.;
Nguyen, Thuc‐Quyen

Publication type:

Article

Quantifying and Understanding Voltage Losses Due to Nonradiative Recombination in Bulk Heterojunction Organic Solar Cells with Low Energetic Offsets.

Published in:

Advanced Energy Materials, 2019, v. 9, n. 27, p. N.PAG, doi. 10.1002/aenm.201901077

By:

Rosenthal, Katie D.;
Hughes, Michael P.;
Luginbuhl, Benjamin R.;
Ran, Niva A.;
Karki, Akchheta;
Ko, Seo‐Jin;
Hu, Huawei;
Wang, Ming;
Ade, Harald;
Nguyen, Thuc‐Quyen

Publication type:

Article

Design of Nonfullerene Acceptors with Near‐Infrared Light Absorption Capabilities.

Published in:

Advanced Energy Materials, 2018, v. 8, n. 26, p. 1, doi. 10.1002/aenm.201801209

By:

Lee, Jaewon;
Ko, Seo‐Jin;
Seifrid, Martin;
Lee, Hansol;
McDowell, Caitlin;
Luginbuhl, Benjamin R.;
Karki, Akchheta;
Cho, Kilwon;
Nguyen, Thuc‐Quyen;
Bazan, Guillermo C.

Publication type:

Article

Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm.

Published in:

Advanced Energy Materials, 2018, v. 8, n. 24, p. 1, doi. 10.1002/aenm.201801212

By:

Lee, Jaewon;
Ko, Seo‐Jin;
Seifrid, Martin;
Lee, Hansol;
Luginbuhl, Benjamin R.;
Karki, Akchheta;
Ford, Michael;
Rosenthal, Katie;
Cho, Kilwon;
Nguyen, Thuc‐Quyen;
Bazan, Guillermo C.

Publication type:

Article

Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells.

Published in:

Advanced Energy Materials, 2016, v. 6, n. 19, p. n/a, doi. 10.1002/aenm.201600637

By:

Lee, Tack Ho;
Uddin, Mohammad Afsar;
Zhong, Chengmei;
Ko, Seo‐Jin;
Walker, Bright;
Kim, Taehyo;
Yoon, Yung Jin;
Park, Song Yi;
Heeger, Alan J.;
Woo, Han Young;
Kim, Jin Young

Publication type:

Article

Solar Cells: Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells (Adv. Energy Mater. 19/2016).

Published in:

Advanced Energy Materials, 2016, v. 6, n. 19, p. n/a, doi. 10.1002/aenm.201670113

By:

Lee, Tack Ho;
Uddin, Mohammad Afsar;
Zhong, Chengmei;
Ko, Seo‐Jin;
Walker, Bright;
Kim, Taehyo;
Yoon, Yung Jin;
Park, Song Yi;
Heeger, Alan J.;
Woo, Han Young;
Kim, Jin Young

Publication type:

Article

Small-Bandgap Polymer Solar Cells with Unprecedented Short-Circuit Current Density and High Fill Factor.

Published in:

Advanced Materials, 2015, v. 27, n. 21, p. 3318, doi. 10.1002/adma.201501132

By:

Choi, Hyosung;
Ko, Seo-Jin;
Kim, Taehyo;
Morin, Pierre-Olivier;
Walker, Bright;
Lee, Byoung Hoon;
Leclerc, Mario;
Kim, Jin Young;
Heeger, Alan J.

Publication type:

Article

An Organic Surface Modifier to Produce a High Work Function Transparent Electrode for High Performance Polymer Solar Cells.

Published in:

Advanced Materials, 2015, v. 27, n. 5, p. 892, doi. 10.1002/adma.201404172

By:

Choi, Hyosung;
Kim, Hak-Beom;
Ko, Seo-Jin;
Kim, Jin Young;
Heeger, Alan J.

Publication type:

Article

Amine-Based Polar Solvent Treatment for Highly Efficient Inverted Polymer Solar Cells.

Published in:

Advanced Materials, 2014, v. 26, n. 3, p. 494, doi. 10.1002/adma.201302991

By:

Lee, Bo Ram;
Jung, Eui Dae;
Nam, Yun Seok;
Jung, Minbok;
Park, Ji Sun;
Lee, Seungjin;
Choi, Hyosung;
Ko, Seo-Jin;
Shin, Na Ra;
Kim, Young-Kuk;
Kim, Sang Ouk;
Kim, Jin Young;
Shin, Hyung-Joon;
Cho, Shinuk;
Song, Myoung Hoon

Publication type:

Article

Multifunctional Conjugated Polymers with Main-Chain Donors and Side-Chain Acceptors for Dye Sensitized Solar Cells (DSSCs) and Organic Photovoltaic Cells (OPVs).

Published in:

Macromolecular Rapid Communications, 2011, v. 32, n. 22, p. 1809, doi. 10.1002/marc.201100447

By:

Chang, Dong Wook;
Ko, Seo-Jin;
Kim, Jin Young;
Park, Su-Moon;
Lee, Hyo Joong;
Dai, Liming;
Baek, Jong-Beom

Publication type:

Article

Hall of Fame Article: Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance (Adv. Mater. 30/2019).

Published in:

Advanced Materials, 2019, v. 31, n. 30, p. N.PAG, doi. 10.1002/adma.201970219

By:

Brus, Viktor V.;
Lee, Jaewon;
Luginbuhl, Benjamin R.;
Ko, Seo‐Jin;
Bazan, Guillermo C.;
Nguyen, Thuc‐Quyen

Publication type:

Article

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance.

Published in:

Advanced Materials, 2019, v. 31, n. 30, p. N.PAG, doi. 10.1002/adma.201900904

By:

Brus, Viktor V.;
Lee, Jaewon;
Luginbuhl, Benjamin R.;
Ko, Seo‐Jin;
Bazan, Guillermo C.;
Nguyen, Thuc‐Quyen

Publication type:

Article

Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells.

Published in:

Carbon Energy, 2020, v. 2, n. 1, p. 131, doi. 10.1002/cey2.20

By:

Ko, Seo‐Jin;
Choi, Hyosung;
Hoang, Quoc Viet;
Song, Chang Eun;
Morin, Pierre‐Olivier;
Heo, Jungwoo;
Leclerc, Mario;
Yoon, Sung Cheol;
Woo, Han Young;
Shin, Won Suk;
Walker, Bright;
Kim, Jin Young

Publication type:

Article

Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells.

Published in:

Carbon Energy, 2020, v. 2, n. 1, p. 131, doi. 10.1002/cey2.20

By:

Ko, Seo‐Jin;
Choi, Hyosung;
Hoang, Quoc Viet;
Song, Chang Eun;
Morin, Pierre‐Olivier;
Heo, Jungwoo;
Leclerc, Mario;
Yoon, Sung Cheol;
Woo, Han Young;
Shin, Won Suk;
Walker, Bright;
Kim, Jin Young

Publication type:

Article

Improved Performance in Polymer Solar Cells Using Mixed PC61BM/PC71BM Acceptors.

Published in:

Advanced Energy Materials, 2015, v. 5, n. 5, p. n/a, doi. 10.1002/aenm.201401687

By:

Ko, Seo‐Jin;
Lee, Wonho;
Choi, Hyosung;
Walker, Bright;
Yum, Seungjib;
Kim, Seongbeom;
Shin, Tae Joo;
Woo, Han Young;
Kim, Jin Young

Publication type:

Article

Works by Ko, Seo‐Jin

Dithieno[3,2- b:2′,3′- d]pyrrole and Benzothiadiazole-Based Semicrystalline Copolymer for Photovoltaic Devices with Indene-C<sub>60</sub> Bisadduct.

Photocurrent Extraction Efficiency near Unity in a Thick Polymer Bulk Heterojunction.

New 3,8‐difluoro indoloindole‐based copolymers for organic solar cell.

Achieving Highly Sensitive Near‐Infrared Organic Photodetectors using Asymmetric Non‐Fullerene Acceptor.

Crystallization‐Driven Optimization of Morphology and Performance in Near‐Infrared Organic Photodetectors via Alkyl Side Chain Tuning of Narrow Bandgap Non‐Fullerene Acceptors.

Low Voltage‐Loss Organic Solar Cells Light the Way for Efficient Semitransparent Photovoltaics.

Organic X‐Ray Image Sensors Using a Medium Bandgap Polymer Donor with Low Dark Current.

Versatile surface plasmon resonance of carbon-dot-supported silver nanoparticles in polymer optoelectronic devices.

Effect of Cyano Substitution on Non‐Fullerene Acceptor for Near‐Infrared Organic Photodetectors above 1000 nm (Adv. Funct. Mater. 8/2023).

Effect of Cyano Substitution on Non‐Fullerene Acceptor for Near‐Infrared Organic Photodetectors above 1000 nm.

Significant Dark Current Suppression in Organic Photodetectors Using Side Chain Fluorination of Conjugated Polymer (Adv. Funct. Mater. 4/2022).

Significant Dark Current Suppression in Organic Photodetectors Using Side Chain Fluorination of Conjugated Polymer.

Conjugated Polymers: Exploring Wholly Doped Conjugated Polymer Films Based on Hybrid Doping: Strategic Approach for Optimizing Electrical Conductivity and Related Thermoelectric Properties (Adv. Funct. Mater. 42/2020).

Exploring Wholly Doped Conjugated Polymer Films Based on Hybrid Doping: Strategic Approach for Optimizing Electrical Conductivity and Related Thermoelectric Properties.

Synthesis of the Copolymer Based on Diketopyrrolopyrrole with Didecyl Chain for OPVs.

Structurally Driven Ultrafast Charge Funneling in Organic Bulk Heterojunction Hole Transport Layer for Efficient Colloidal Quantum Dot Photovoltaics (Adv. Energy Mater. 20/2023).

Structurally Driven Ultrafast Charge Funneling in Organic Bulk Heterojunction Hole Transport Layer for Efficient Colloidal Quantum Dot Photovoltaics.

Rational Design of Highly Efficient Semi‐Transparent Organic Photovoltaics with Silver Nanowire Top Electrode via 3D Optical Simulation Study.

Temperature and Light Modulated Open‐Circuit Voltage in Nonfullerene Organic Solar Cells with Different Effective Bandgaps.

Quantifying the Nongeminate Recombination Dynamics in Nonfullerene Bulk Heterojunction Organic Solar Cells.

Quantifying and Understanding Voltage Losses Due to Nonradiative Recombination in Bulk Heterojunction Organic Solar Cells with Low Energetic Offsets.

Design of Nonfullerene Acceptors with Near‐Infrared Light Absorption Capabilities.

Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm.

Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells.

Solar Cells: Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells (Adv. Energy Mater. 19/2016).

Small-Bandgap Polymer Solar Cells with Unprecedented Short-Circuit Current Density and High Fill Factor.

An Organic Surface Modifier to Produce a High Work Function Transparent Electrode for High Performance Polymer Solar Cells.

Amine-Based Polar Solvent Treatment for Highly Efficient Inverted Polymer Solar Cells.

Multifunctional Conjugated Polymers with Main-Chain Donors and Side-Chain Acceptors for Dye Sensitized Solar Cells (DSSCs) and Organic Photovoltaic Cells (OPVs).

Hall of Fame Article: Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance (Adv. Mater. 30/2019).

Solution‐Processed Semitransparent Organic Photovoltaics: From Molecular Design to Device Performance.

Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells.

Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells.

Improved Performance in Polymer Solar Cells Using Mixed PC<sub>61</sub>BM/PC<sub>71</sub>BM Acceptors.