Insights into solvent vapor annealing on the performance of bulk heterojunction solar cells by a quantitative nanomorphology study

Liao, Hsin-Ya; Tsao, Cheng‐Si; Huang, Yu‐Ching; Jao, Meng‐Huan; Tien, Kai-Ying; Chuang, Chih-Min; Chen, C.-Y.; Su, Chi‐Cheung; Jeng, U‐Ser; Chen, Y.-F.; Su, Wei‐Fang

doi:10.1039/c3ra45619f

Cited by 28 publications

(17 citation statements)

References 34 publications

(62 reference statements)

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“…On the other side, after treated by SVA, hole mobility increased to 9.4  10 -5 cm 2 /Vs, which corresponds to approximately an order of magnitude enhancement, while electron mobility remained nearly unchanged (~3.6  10 -4 cm 2 /Vs). As a result of improved charge balance, the overall device performance was dramatically improved except that V OC decreased slightly to 0.77 V, similar with the results in many other literature [11], [22]- [24]. The reduction of V OC can be attributed to the lowering in quasi-Fermi levels for electron and hole transport due to a depleted steady carrier density [25], [26].…”

Section: Resultssupporting

confidence: 87%

Improving Organic Solar Cells Efficiency Through a Two-Step Method Consisting of Solvent Vapor Annealing and Thermal Annealing

Cai

Miao

Yan

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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Abstract-The realization of high efficiency organic small molecule: fullerene solar cells is challenging but become more and more feasible due to the rapid development in donor materials and device fabrication techniques. In the past several years, the optimization in the processing techniques, such as, solvent vapor annealing the use of solvent additives had lead to superior improvement in device performance of organic solar cells from different donor systems, but at an expense of reduction in open-circuit voltage (V OC ). In this paper, we report the overall device performance of organic small molecule solar cells (SMSCs) can be significantly enhanced through a two-step process consisting of solvent vapor annealing (SVA) and thermal annealing (TA) (short for SVA+TA), especially the reduction in V OC can be effectively avoided in case of exclusive use of solvent vapor annealing. The carrier dynamics is determined by transient photovoltage (TPV) and transient photocurrent (TPC) measurements, which can provide information on the origin of enhanced device performance upon the two-step annealing. The observed V OC recovery is attributed to preferable change in charge dynamic, thus leading to a superior overall device performance. Furthermore, the SVA and the consequential TA are complementary to each other, thus the two-step annealing method represents a feasible route to simultaneously improve the V OC , J SC , FF and PCE of small molecule solar cells. Index Terms-small molecule solar cells (SMSCs), solvent vapor annealing (SVA), thermal annealing (TA), transient photovoltage (TPV), transient photocurrent (TPC), and bimolecular recombination 1077-260X (c)

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Section: Resultssupporting

confidence: 87%

Improving Organic Solar Cells Efficiency Through a Two-Step Method Consisting of Solvent Vapor Annealing and Thermal Annealing

Cai

Miao

Yan

et al. 2016

IEEE J. Select. Topics Quantum Electron.

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“…On the other hand, mobility of electron of approximately 3.6 × 10 -4 cm 2 / Vs does not change. In summary, the overall performance of device was dramatically improved whereby a slight decrease in V oc of 0.77 V was observed, as previously reported [11,[22][23][24]. The cause of decrease in V oc is linked with the decrease in Quasi-Fermi levels for the transport of hole and electron [25,26].…”

Section: Resultssupporting

confidence: 60%

Efficiency Improvement of Organic Solar Cells Using Two-step Annealing Technique

Masood¹,

Haider²,

Nawaz³

2016

Transactions on Electrical and Electronic Materials

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The fullerene solar cells are becoming a feasible choice due to the advanced developments in donor materials and improved fabrication techniques of devices. Recently, sufficient optimization and improvements in the processing techniques like incorporation of solvent vapor annealing (SVA) with additives in solvents has become a major cause of prominent improvements in the performance of organic solar cell-based devices . On the other hand, the challenge of reduced open circuit voltage (V oc ) remains. This study presents an approach for significant performance improvement of overall device based on organic small molecular solar cells (SMSCs) by following a two step technique that comprises thermal annealing (TA) and SVA (abbreviated as SVA+TA). In case of exclusive use of SVA, reduction in V oc can be eliminated in an effective way. The characteristics of charge carriers can be determined by the measurement of transient photo-voltage (TPV) and transient photo-current (TPC) that determines the scope for improvement in the performance of device by two step annealing. The recovery of reduced V oc is linked with the necessary change in the dynamics of charge that lead to increased overall performance of device. Moreover, SVA and TA complement each other; therefore, two step annealing technique is an appropriate way to simultaneously improve the parameters such as V oc , fill factor (FF), short circuit current density (J sc ) and PCE of small molecular solar cells.

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“…SVA in controlling the nanomorphology of block copolymers has been well established in the past decade . Most recently, it has been applied to OPVs . In SVA, solvent vapor can penetrate into the blend and drastically lower the glass transition temperature of the materials, and thus polymers/molecules in blends gain high mobility to organize into a lower energy state.…”

Section: Solvent Properties Used In Sva and Opv Performance Parametermentioning

confidence: 99%

“…When applying SVA into small‐molecule BHJ blends, phase separation and nucleation and growth will be two processes that dominate the kinetics of morphology evolution. Thus, a systematic study of the morphology change during SVA treatment, and correlating the morphology details with device performance are of high importance. In this study, we performed a systematic SVA study on a BHJ photoactive layer based on the DR3TBDTT molecule ( Figure a) (DR3TBDTT:[6,6]‐phenyl‐C 71 ‐butyric acid methyl ester (PC 71 BM)) and elucidated the morphology reasons for device performance improvement.…”

Section: Solvent Properties Used In Sva and Opv Performance Parametermentioning

confidence: 99%

Subtle Balance Between Length Scale of Phase Separation and Domain Purification in Small‐Molecule Bulk‐Heterojunction Blends under Solvent Vapor Treatment

et al. 2015

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A series of solvents with different solubilities for DR3TBDTT and PC71 BM, and different boiling points, is used for solvent vapor annealing (SVA) treatment to systematically investigate the solvent-morphology-performance relationship. The presence of solvent molecules inside bulk-heterojunction (BHJ) thin films promotes the mobility of both donor and acceptor molecules, leading to crystallization and aggregation, which are important in modulating morphology.

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Insights into solvent vapor annealing on the performance of bulk heterojunction solar cells by a quantitative nanomorphology study

Cited by 28 publications

References 34 publications

Improving Organic Solar Cells Efficiency Through a Two-Step Method Consisting of Solvent Vapor Annealing and Thermal Annealing

Improving Organic Solar Cells Efficiency Through a Two-Step Method Consisting of Solvent Vapor Annealing and Thermal Annealing

Efficiency Improvement of Organic Solar Cells Using Two-step Annealing Technique

Subtle Balance Between Length Scale of Phase Separation and Domain Purification in Small‐Molecule Bulk‐Heterojunction Blends under Solvent Vapor Treatment

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