Query: efficient solution-processed bulk heterojunction solar cells

Candidate papers:

abstract: Research on small molecule based organic semiconductors has undoubtedly been strongly influenced by xerographic photoconductors like triarylamines, the first important organic electronic materials in market products. Their development was strongly influenced by the B ssler model, which provided a rationale for the design of amorphous organic photoand semiconductors. According to this model, only compounds that lack dipole moments are considered promising for charge carrier transport because the increased energetic disorder associated with dipole moments is thought to impede charge hopping. Recently, we questioned this paradigm in the field of organic photovoltaics (OPV) and successfully implemented highly dipolar merocyanine dyes as active components for light harvesting as well as exciton and hole transport in solution cast bulk heterojunction (BHJ) solar cells. The rationale behind our concept was that highly dipolar donor acceptor (D A) substituted p systems (also called push pull dyes) self assemble into centrosymmetric dimers, thus effectively eliminating molecular dipole moments on the supramolecular and material levels. Two drawbacks of our BHJ materials, however, limited the acceptance of our concept so far. Firstly, the best solar cells were obtained for merocyanine dyes whose molecular scaffolds were equipped with rather bulky substituents that interfere with close face to face antiparallel dimerization. Secondly, the power conversion efficiencies (h) under standard AM1.5, 100 mW cm 2 simulated solar illumination conditions for solution cast BHJ cells with fullerenes although significantly advanced by more sophisticated vacuum processing could not be improved beyond 2.6% which is significantly lower than the best solutionprocessed small molecule based BHJ devices fabricated with A D A and D A D chromophores, for example, acceptorsubstituted oligothiophenes (up to 3.7% and triarylamines (up to 4.3% diketopyrrolopyrroles (up to 4.4% and squaraines (up to 5.2 Herein, we introduce dipolar D A dyes with flat structures that undoubtedly form centrosymmetric dimers with perfectly cancelled dipole moments in the solid state. Solution processed BHJ solar cells derived thereof exhibit power conversion efficiencies up to 4.5 5.1% (dependent on light intensity) clearly placing D A dyes now among the top performing small molecules in the field of organic photovoltaics. Scheme 1 outlines the synthetic route that follows our earlier work on merocyanine dyes for photorefractive materials and the simple access to 5 dialkylamino thiophene 2carbaldehydes by Hartmann. Detailed synthetic procedures and characterization data are described in the Supporting Information.
author_names: Hannah Burckstummer

Elena V Tulyakova

Manuela Deppisch

Martin R Lenze

Nils M Kronenberg

Marcel Gsanger

Matthias Stolte

Klaus Meerholz

Frank Wurthner
title: Efficient solution processed bulk heterojunction solar cells by antiparallel supramolecular arrangement of dipolar donor acceptor dyes.
venue: Angewandte Chemie
year: 2011

abstract: A solution processed small molecule with low band gap, dicyanovinyl substituted oligothiophene (DCN7T) was used as the donor in bulk heterojunctions solar cells and a power conversion efficiency of 2.45% has been obtained for the device using simply spin coating without special treatment.
author_names: Yongsheng Liu

Xiangjian Wan

Bin Yin

Jiaoyan Zhou

Guankui Long

Shougen Yin

Yongsheng Chen
title: Efficient solution processed bulk heterojunction solar cells based a donor acceptor oligothiophene
year: 2010

abstract: A conjugated acceptor donor acceptor (A p D p A) with the Zn porphyrin core and the di cyanovinyl substituted thiophene (A) connected at meso positions denoted as was designed and synthesized. The optical and electrochemical properties of were investigated. This new porphyrin exhibits a broad and intense absorption in the visible and near infrared regions. Bulk heterojunction (BHJ) solution processed organic solar cells based on this porphyrin, as electron donor material, and PC71BM [6,6] phenyl C71 butyric acid methyl ester) as electron acceptor material, were fabricated using THF and a pyridine THF solvent exhibiting a power conversion efficiency of 3.65% and 5.24% respectively. The difference in efficiencies is due to the enhancement of the short circuit current J(sc) and FF of the solar cell, which is ascribed to a stronger and broader incident photon to current efficiency (IPCE) response and a better balanced charge transport in the device processed with the pyridine THF solvent.
author_names: Challuri Vijay Kumar

Lydia Cabau

Emmanuel N Koukaras

Ganesh D Sharma

Emilio Jose Palomares
title: Synthesis, optical and electrochemical properties of the A p D p A porphyrin and its application as an electron donor in efficient solution processed bulk heterojunction solar cells.
venue: Nanoscale
year: 2015

abstract: Efficient conventional bulk heterojunction (BHJ) perovskite hybrid solar cells (pero HSCs) solution processed from a composite of CH3NH3PbI3 mixed with PC61BM [6,6] phenyl C61 butyric acid methyl ester) where CH3NH3PbI3 acts as the electron donor and PC61BM acts as the electron acceptor, are reported for the first time. The efficiency of 12.78% is twofold enhancement in comparison with the conventional planar heterojunction pero HSCs (6.90% fabricated by pristine CH3NH3PbI3. The BHJ pero HSCs are further optimized by using PC61BM/TiO2 bi electron extraction layer (EEL) which are both solution processed and then followed with low temperature thermal annealing. Due to higher electrical conductivity of PC61BM over that of TiO2, an efficiency of 14.98% the highest reported efficiency for the pero HSCs without incorporating high temperature processed mesoporous TiO2 and Al2O3 as the EEL and insulating scaffold, is observed from PC61BM modified BHJ pero HSCs. Thus, the findings provide a simple way to approach high efficiency low cost pero HSCs.
author_names: Chang Liu

Kai Wang

Pengcheng Du

Chao Yi

Tianyu Meng

Xiong Gong
title: Efficient Solution Processed Bulk Heterojunction Perovskite Hybrid Solar Cells
year: 2015

abstract: Abstract Two molecules denoted as VC96 and VC97 have been synthesized for efficient e 6.13% 100 mW/cm 2 sun simulated light) small molecule solution processed organic solar cells. These molecules have been designed with the D 1 A D 2 A D 1 structure bearing different central donor unit, same benzothiadiazole (BT) as p acceptor and end capping triphenylamine. Moreover, the optical and electrochemical properties (both experimental and theoretical) of these molecules have been systematically investigated. The solar cells prepared from VC96 :PC 71 BM and VC97 :PC 71 BM (1:2) processed from CF (chloroform) exhibit a PCE (power conversion efficiency) of e 4.06% J sc 8.36 mA/cm 2 V oc 0.90 V and FF 0.54) and e 3.12% J sc 6.78 mA/cm 2 V oc 0.92 V and FF 0.50) respectively. The higher PCE of the device with VC96 as compared to VC97 is demonstrated to be due to the higher hole mobility and broader IPCE spectra. The devices based on VC96 :PC 71 BM and VC97 :PC 71 BM processed with solvent additive (3 v% DIO, 1,8 diiodooctane) showed PCE of e 5.44% and e 4.72% respectively. The PCE device of optimized VC96 :PC 71 BM processed with DIO/CF (thermal annealed) has been improved up to 6.13% J sc 10.72 mA/cm 2 V oc 0.88 V and FF 0.61) The device optimization results from the improvement of the balanced charge transport and better nanoscale morphology induced by the solvent additive plus the thermal annealing.
author_names: Challuri Vijay Kumar

Lydia Cabau

Emmanuel N Koukaras

Ganesh D Sharma

Emilio Jose Palomares
title: Efficient solution processed D1 A D2 A D1 small molecules bulk heterojunction solar cells based on alkoxy triphenylamine and benzo[1,2 b:4,5 b']thiophene units
year: 2015

abstract: The work reported here was supported by the King Abdullah University of Science and Technology (KAUST)
author_names: Flurin D Eisner

Akmaral Seitkhan

Yang Han

Dongyoon Khim

Emre Yengel

Ahmad R Kirmani

Jixian Xu

F Pelayo Garcia Arquer

Edward H Sargent

Aram Amassian

Zhuping Fei

Martin Heeney

Thomas D Anthopoulos
title: Solution Processed In2O3/ZnO Heterojunction Electron Transport Layers for Efficient Organic Bulk Heterojunction and Inorganic Colloidal Quantum Dot Solar Cells
year: 2018

abstract: In this study, we employed polyethylenimine doped sol gel processed zinc oxide composites (ZnO:PEI) as efficient electron transport layers (ETL) for facilitating electron extraction in inverted polymer solar cells. Using ultraviolet photoelectron spectroscopy, synchrotron grazing incidence small angle X ray scattering and transmission electron microscopy, we observed that ZnO:PEI composite films' energy bands could be tuned considerably by varying the content of PEI up to 7 wt the conduction band ranged from 4.32 to 4.0 eV and the structural order of ZnO in the ZnO:PEI thin films would be enhanced to align perpendicular to the ITO electrode, particularly at 7 wt PEI, facilitating electron transport vertically. We then prepared two types of bulk heterojunction systems based on poly(3 hexylthiophene) (P3HT):phenyl C61 butryric acid methyl ester (PC61BM) and benzo[1,2 b:4,5 b]dithiophene thiophene 2,1,3 benzooxadiazole (PBDTTBO):phenyl C71 butryric acid methyl ester (PC71BM) that incorporated the ZnO:PEI composite layers. When using a composite of ZnO:PEI (93:7, w/w) as the ETL, the power conversion efficiency (PCE) of the P3HT:PC61BM (1:1, w/w) device improved to 4.6% from a value of 3.7% for the corresponding device that incorporated pristine ZnO as the ETL a relative increase of 24% For the PBDTTBO:PC71BM (1:2, w/w) device featuring the same amount of PEI blended in the ETL, the PCE improved to 8.7% from a value of 7.3% for the corresponding device that featured pure ZnO as its ETL a relative increase of 20% Accordingly, ZnO:PEI composites can be effective ETLs within organic photovoltaics.
author_names: Hsiu-Cheng Chen

Shu-Wei Lin

Jian-ming Jiang

Yu-Wei Su

Kung-Hwa Wei
title: Solution processed zinc oxide/polyethylenimine nanocomposites as tunable electron transport layers for highly efficient bulk heterojunction polymer solar cells.
venue: ACS applied materials interfaces
year: 2015

abstract: In this study we used simultaneous grazing incidence small and wide angle X ray scattering (GISAXS and GIWAXS, respectively) to probe the multilength scale structures of thin active layers comprising the linear A D A type p conjugated donor molecule TBDTCNR and the fullerene acceptor molecule PC61BM for use in solution processed small molecule based organic solar cells (SMOSCs) We found that the pseudo two dimensional fractal like networks in the bulk heterojunction (BHJ) structure were determined by mutual interactions between the small molecule (SM) crystallites and the nanoscale PC61BM clusters during their formation and phase separation, and deduced quantitatively, at multiple length scales, the BHJ structures comprising these SM crystallites and PC61BM clusters. We also conducted in situ GIWAXS measurements to study the temporal behavior and kinetics of SM crystallization from solution to the solid film state. Our GISAXS/GIWAXS study revealed that the multilength scale BHJ structures in the thin fi.
author_names: Yu-Ching Huang

Cheng-Si Tsao

Tzu-Yen Huang

Hou-Chin Cha

Dhananjaya Patra

Chun-Jen Su

U-Ser Jeng

Kuo-Chuan Ho

Kung-Hwa Wei

Chih-Wei Chu
title: Quantitative Characterization and Mechanism of Formation of Multilength scale Bulk Heterojunction Structures in Highly Efficient Solution Processed Small Molecule Organic Solar Cells
year: 2015

abstract: We report the synthesis, characterization, and optical and electrochemical of properties of two novel molecules DRT3 BDT (1) and DTT3 BDT (2) comprising the same BDT central core (donor) and different end capped acceptor units, i.e. rhodanine with ethyl hexyl and thiazolidione with ethylhexyl, respectively, linked via an alkyl substituted terthiophene (3 T) p conjugation bridge. The electrochemical properties of these small molecules indicate that their energy levels are compatible with energy levels of PC71BM for efficient exciton dissociation. These molecules have been used as electron donors along with PC71BM as an electron acceptor, for the fabrication of solution processed "small molecule" bulk heterojunction (BHJ) solar cells (smOPV) The device prepared from optimized 1:PC71BM(1:1) processed cast from DIO (3%v)/CF solvent exhibited a power conversion efficiency of 6.76% with Jsc 11.92 mA cm( 2) Voc 0.90 and FF 0.63. The device with 2:PC71BM under the same conditions showed a lower PCE of 5.25% with Jsc 10.52 mA cm( 2) Voc 0.86 and FF 0.56. The AFM, TEM and PL quenching measurements revealed that the high Jsc is a result of the appropriate morphology and exciton dissociation. The performances were compared for the devices based on two small molecules. The higher Jsc for device 1 was attributed to its better nanoscale phase separation, smooth surface and higher carrier mobility in the 1:PC71BM blend film. Moreover, the higher value of FF for the 1:PC71BM based device was ascribed to a good balance between the electron and hole mobilities.
author_names: Challuri Vijay Kumar

Lydia Cabau

Emmanuel N Koukaras

Shahbaz Ahmed Siddiqui

Ganesh D Sharma

Emilio Jose Palomares
title: Efficient bulk heterojunction solar cells based on solution processed small molecules based on the same benzo[1,2 b:4, 5 b']thiophene unit as core donor and different terminal units.
venue: Nanoscale
year: 2015

abstract: We demonstrate the efficiency enhancement and efficient hole extraction achieved by undoped Si nanocrystals (NCs) and p type Si (p Si) NCs in solution processed bulk heterojunction (BHJ) organic solar cells (OSCs) and planar heterojunction (PHJ) perovskite solar cells (PrSCs) We observed that the surface coverage of Si NCs on the substrate significantly affected the photovoltaic performance of the BHJ OSCs and PHJ PrSCs. The undoped Si NCs and p Si NCs enhanced the power conversion efficiencies (PCEs) of the BHJ OSCs by ~6% and ~11% respectively, and those of PHJ PrSCs by ~22% and ~23% correspondingly, compared with the PCEs of devices without Si NCs. The p Si NCs had a highest occupied molecular orbital (HOMO) energy level ~0.16 eV higher than that of undoped Si NCs and showed better balances with the HOMO energy levels of the PTB7 Th and MAPbI3 perovskite materials, achieving an increase in the hole mobility of the BHJ system, and thus demonstrating their key role as hole extracting materials.
author_names: Hanbin Jeong

Hansol Kim

Won-Il Song

Kyung-Hoon Yoo

Jason Eric Rama

Jae Kwan Lee
title: Improved efficiency of solution processed bulk heterojunction organic solar cells and planar heterojunction perovskite solar cells with efficient hole extracting Si nanocrystals
year: 2016