Enhanced efficiency of polymer solar cells through synergistic optimization of mobility and tuning donor alloys by adding high-mobility conjugated polymers

A diketopyrrolopyrrole-based small bandgap polymer (DPPT-TT) with high mobility is introduced as an additive to D–A1–D–A2 type thieno[3,4-b]thiophene-based random copolymer (P3):(6,6)-phenyl-C70-butyric acid methyl ester (PC71BM) polymer solar cells (PSCs). The average power conversion efficiencies (PCEs) were improved from 6.15% to 8.30% with the addition of 0.5% DPPT-TT. The photocurrent density versus effective voltage (Jph–Veff) curves, short-circuit current density (JSC) and open circuit voltage (VOC) as functions of incident light intensity, photoluminescence (PL) and time-resolved transient PL (TRTPL) spectra were investigated, and the results certified the effect of DPPT-TT as the third component material in terms of efficient exciton dissociation and weakened charge carrier recombination. The relationship between VOC and the weight ratio of DPPT-TT was explained with density functional theory (DFT) calculations and the electron density of states of unit mass (Ne), indicating the formation of a polymer alloy in ternary blend. With proper addition of DPPT-TT, the mobility of electrons and holes becomes more balanced and the efficiency of exciton utilization is improved due to the existence of Forster resonance energy transfer (FRET), which also contributes to the enhanced JSC and PCEs. Our work demonstrates that appropriate donor polymers forming a polymer alloy in blend is a rational strategy to improve photovoltaic performance.

[1]  Zhaojun Li,et al.  High-performance all-polymer solar cells based on fluorinated naphthalene diimide acceptor polymers with fine-tuned crystallinity and enhanced dielectric constants , 2018 .

[2]  A. Heeger,et al.  Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells , 2016 .

[3]  Juliane Kniepert,et al.  Nongeminate and Geminate Recombination in PTB7:PCBM Solar Cells , 2014, 2106.10101.

[4]  M. Halik,et al.  Morphology analysis of near IR sensitized polymer/fullerene organic solar cells by implementing low bandgap heteroanalogue C-/Si-PCPDTBT , 2014 .

[5]  Wei Zhang,et al.  Ternary Organic Solar Cells with Minimum Voltage Losses , 2017 .

[6]  F. Liu,et al.  Achieving High‐Performance Ternary Organic Solar Cells through Tuning Acceptor Alloy , 2017, Advanced materials.

[7]  Prashant Sonar,et al.  A High Mobility P‐Type DPP‐Thieno[3,2‐b]thiophene Copolymer for Organic Thin‐Film Transistors , 2010, Advanced materials.

[8]  B. Thompson,et al.  Compositional dependence of the open-circuit voltage in ternary blend bulk heterojunction solar cells based on two donor polymers. , 2012, Journal of the American Chemical Society.

[9]  Shi-jian Su,et al.  Ternary Organic Solar Cells with Coumarin7 as the Donor Exhibiting Greater Than 10% Power Conversion Efficiency and a High Fill Factor of 75. , 2017, ACS applied materials & interfaces.

[10]  Renqiang Yang,et al.  Balancing High Open Circuit Voltage over 1.0 V and High Short Circuit Current in Benzodithiophene‐Based Polymer Solar Cells with Low Energy Loss: A Synergistic Effect of Fluorination and Alkylthiolation , 2018 .

[11]  A. Heeger,et al.  Polymer–Polymer Förster Resonance Energy Transfer Significantly Boosts the Power Conversion Efficiency of Bulk‐Heterojunction Solar Cells , 2015, Advanced materials.

[12]  Xuncheng Liu,et al.  Low band gap conjugated polymers combining siloxane-terminated side chains and alkyl side chains: side-chain engineering achieving a large active layer processing window for PCE > 10% in polymer solar cells , 2017 .

[13]  Joshua H. Carpenter,et al.  High‐Efficiency Nonfullerene Organic Solar Cells: Critical Factors that Affect Complex Multi‐Length Scale Morphology and Device Performance , 2017 .

[14]  Christoph J. Brabec,et al.  Performance Enhancement of the P3HT/PCBM Solar Cells through NIR Sensitization Using a Small‐Bandgap Polymer , 2012 .

[15]  Henning Sirringhaus,et al.  Device Physics of Solution‐Processed Organic Field‐Effect Transistors , 2005 .

[16]  Donal D. C. Bradley,et al.  Device annealing effect in organic solar cells with blends of regioregular poly(3-hexylthiophene) and soluble fullerene , 2005 .

[17]  S. Kim,et al.  Selective Electron‐ or Hole‐Transport Enhancement in Bulk‐Heterojunction Organic Solar Cells with N‐ or B‐Doped Carbon Nanotubes , 2011, Advanced materials.

[18]  Luping Yu,et al.  The role of N-doped multiwall carbon nanotubes in achieving highly efficient polymer bulk heterojunction solar cells. , 2013, Nano letters.

[19]  W. Shen,et al.  High-performance ternary polymer solar cells from a structurally similar polymer alloy , 2017 .

[20]  Yufei Wang,et al.  36% Enhanced Efficiency of Ternary Organic Solar Cells by Doping a NT-Based Polymer as an Electron-Cascade Donor , 2018, Polymers.

[21]  Renqiang Yang,et al.  Regulating Molecular Aggregations of Polymers via Ternary Copolymerization Strategy for Efficient Solar Cells. , 2017, ACS applied materials & interfaces.

[22]  H. Ohkita,et al.  Selective Dye Loading at the Heterojunction in Polymer/Fullerene Solar Cells , 2011 .

[23]  Fujun Zhang,et al.  Efficient ternary non-fullerene polymer solar cells with PCE of 11.92% and FF of 76.5% , 2018 .

[24]  Renqiang Yang,et al.  Significantly Enhancing the Efficiency of a New Light‐Harvesting Polymer with Alkylthio naphthyl Substituents Compared to Their Alkoxyl Analogs , 2018 .

[25]  Junbiao Peng,et al.  New insight of molecular interaction, crystallization and phase separation in higher performance small molecular solar cells via solvent vapor annealing , 2016 .

[26]  A. Heeger,et al.  Effects of Solvent Additives on Morphology, Charge Generation, Transport, and Recombination in Solution‐Processed Small‐Molecule Solar Cells , 2014 .

[27]  B. Thompson,et al.  Structural Origins for Tunable Open‐Circuit Voltage in Ternary‐Blend Organic Solar Cells , 2015 .

[28]  Daoben Zhu,et al.  An Electron Acceptor Challenging Fullerenes for Efficient Polymer Solar Cells , 2015, Advanced materials.

[29]  Yongsheng Chen,et al.  Nonfullerene Tandem Organic Solar Cells with High Performance of 14.11% , 2018, Advanced materials.

[30]  Fujun Zhang,et al.  Efficient organic ternary solar cells with the third component as energy acceptor , 2016 .

[31]  Kai Sun,et al.  Solvent‐Annealed Crystalline Squaraine: PC70BM (1:6) Solar Cells , 2011 .

[32]  Feng Liu,et al.  Single-junction polymer solar cells with high efficiency and photovoltage , 2015, Nature Photonics.

[33]  B. Thompson,et al.  Efficient ternary blend bulk heterojunction solar cells with tunable open-circuit voltage. , 2011, Journal of the American Chemical Society.

[34]  Jin Young Kim,et al.  Processing additives for improved efficiency from bulk heterojunction solar cells. , 2008, Journal of the American Chemical Society.

[35]  Shuguang Wen,et al.  Thienothiophene-based copolymers for high-performance solar cells, employing different orientations of the thiazole group as a π bridge , 2017 .

[36]  Hongzheng Chen,et al.  Highly efficient hybrid solar cells with tunable dipole at the donor-acceptor interface. , 2014, Nanoscale.

[37]  Stephen C. Moratti,et al.  EXCITON DIFFUSION AND DISSOCIATION IN A POLY(P-PHENYLENEVINYLENE)/C60 HETEROJUNCTION PHOTOVOLTAIC CELL , 1996 .

[38]  Xiao-Fang Jiang,et al.  Improved Morphology and Efficiency of Polymer Solar Cells by Processing Donor–Acceptor Copolymer Additives , 2016 .

[39]  Liming Ding,et al.  Ternary organic solar cells offer 14% power conversion efficiency. , 2017, Science bulletin.

[40]  Xiong Gong,et al.  Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology , 2005 .

[41]  Shuguang Wen,et al.  Cyclic alkyl chains promote the polymer self-assembly and packing orders for solar cells , 2017 .

[42]  Jun Li,et al.  Enhanced efficiency of polymer solar cells by adding a high-mobility conjugated polymer , 2015 .

[43]  Yun Zhang,et al.  Molecular Optimization Enables over 13% Efficiency in Organic Solar Cells. , 2017, Journal of the American Chemical Society.

[44]  Daoben Zhu,et al.  Small‐Molecule Solar Cells with Fill Factors up to 0.75 via a Layer‐by‐Layer Solution Process , 2014 .

[45]  F. Huang,et al.  Ternary Solar Cells Based on Two Small Molecule Donors with Same Conjugated Backbone: The Role of Good Miscibility and Hole Relay Process. , 2017, ACS applied materials & interfaces.

[46]  Christoph J. Brabec,et al.  Organic Ternary Solar Cells: A Review , 2013, Advanced materials.

[47]  Hongkyu Kang,et al.  Overcoming the Light‐Soaking Problem in Inverted Polymer Solar Cells by Introducing a Heavily Doped Titanium Sub‐Oxide Functional Layer , 2015 .

[48]  Renqiang Yang,et al.  High Extinction Coefficient Thieno[3,4-b]thiophene-Based Copolymer for Efficient Fullerene-Free Solar Cells with Large Current Density , 2017 .

[49]  Yang Yang,et al.  High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends , 2005 .

[50]  Gang Li,et al.  Effect of self-organization in polymer/fullerene bulk heterojunctions on solar cell performance , 2006 .

[51]  Yongfang Li,et al.  Efficient ternary blend polymer solar cells with indene-C60 bisadduct as an electron-cascade acceptor , 2014 .

[52]  Thuc‐Quyen Nguyen,et al.  Monomolecular and Bimolecular Recombination of Electron–Hole Pairs at the Interface of a Bilayer Organic Solar Cell , 2017 .

[53]  Yu-Shan Cheng,et al.  Single Junction Inverted Polymer Solar Cell Reaching Power Conversion Efficiency 10.31% by Employing Dual-Doped Zinc Oxide Nano-Film as Cathode Interlayer , 2014, Scientific Reports.

[54]  Runnan Yu,et al.  Recent Progress in Ternary Organic Solar Cells Based on Nonfullerene Acceptors , 2018 .

[55]  Long Ye,et al.  From Binary to Ternary Solvent: Morphology Fine‐tuning of D/A Blends in PDPP3T‐based Polymer Solar Cells , 2012, Advanced materials.

[56]  Yongfang Li,et al.  Origin of Efficient Inverted Nonfullerene Organic Solar Cells: Enhancement of Charge Extraction and Suppression of Bimolecular Recombination Enabled by Augmented Internal Electric Field. , 2017, The journal of physical chemistry letters.

[57]  Jie Zhu,et al.  Over 14% Efficiency in Organic Solar Cells Enabled by Chlorinated Nonfullerene Small‐Molecule Acceptors , 2018, Advanced materials.