Nongeminate Recombination of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>a</mml:mi></mml:math>-Si: H

Mort, J.; Chen, I.; Troup, A.; Morgan, M.; Knights, J. C.; Lujan, R.

doi:10.1103/physrevlett.45.1348

Cited by 45 publications

(7 citation statements)

References 8 publications

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“…The TDCF [38][39][40][41] in a modified setup was used. In a TDCF measurement free charges are generated by a light pulse.…”

Section: Methodsmentioning

confidence: 99%

“…The TDCF technique is a valuable tool to quantify the charge carrier concentrations as a function of voltage and is frequently applied on OSC. [38][39][40][41] The details are described in the Experimental Section. The results which are shown in Table 1 support strongly our findings from the PL measurements that the charge carrier density in the bulk of the device is hardly affected by surface recombination.…”

Section: Charge Carrier Extractionmentioning

confidence: 99%

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On the Impact of Contact Selectivity and Charge Transport on the Open‐Circuit Voltage of Organic Solar Cells

Spies

List

Sarkar

et al. 2016

Advanced Energy Materials

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However, in comparison to established inorganic-based photovoltaic technologies organic solar cells possess still a much lower efficiency. [2,[9][10][11][12] The efficiency η of solar cells is determined bywhere J SC is the short-circuit current density, V OC is the open-circuit voltage, FF is the fill factor, and P in is the incident power density. The relatively poor transport properties (low mobilities) of the disordered organic materials [13,14] applied in OSC lead to a strong accumulation of charge carriers under current flow and thus to an increase in nongeminate recombination. [10] Consequently, the FF is reduced and for cases of extremely low charge carrier mobilities also J SC , which results in a low overall power conversion efficiency. [10,11,15] Further, due to the relatively low permittivity of the organic materials a significant fraction of the absorbed photon energy is required as driving force for the exciton dissociation of the coulombic bound electron-hole pair (offset between the lowest unoccupied molecular orbitals of donor and acceptor) which lowers the achievable power conversion efficiency significantly. [9] In addition to the latter, a key loss mechanism originates from additional nonradiative recombination pathways. Besides the nongeminate recombination via trap states as a first order recombination process, the recombination at the electrodes, i.e., surface recombination, is an additional loss channel. Surface recombination in OSC was investigated intensively in different perspectives which indicates the importance of a thorough understanding of the underlying mechanisms. [16][17][18][19][20] Kirchartz et al. derived the ideality factor differentially by the light intensity dependence of the open-circuit voltage and demonstrated that the presence of surface recombination leads to the occurrence of an ideality factor n id < 1. [18] But also the charge carrier mobility µ dependent efficiency of OSC has been investigated in terms of surface recombination. It seems to be counterintuitive to assume that the device efficiency is maximum at a finite optimum mobility. Yet, this case is in detail discussed by Deibel et al. and Kirchartz et al., who showed that an optimum mobility exists in the presence of not ideally selective contacts and that faster kinetics by mobilities higher than the optimum will result in a reduction of the overall efficiency. [21,22] TressThe selectivity of electrodes of solar cells is a critical factor that can limit the overall efficiency. If the selectivity of an electrode is not sufficient both electrons and holes recombine at its surface. In materials with poor transport properties such as in organic solar cells, these surface recombination currents are accompanied by large gradients of the quasi-Fermi energies as the driving force. Experimental results from current-voltage characteristics, advanced photo-and electroluminescence as well as charge extraction of three different photoactive materials are shown and compared to drift-diffusion simulations. It can be conc...

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“…The TDCF [38][39][40][41] in a modified setup was used. In a TDCF measurement free charges are generated by a light pulse.…”

Section: Methodsmentioning

confidence: 99%

Section: Charge Carrier Extractionmentioning

confidence: 99%

On the Impact of Contact Selectivity and Charge Transport on the Open‐Circuit Voltage of Organic Solar Cells

Spies

List

Sarkar

et al. 2016

Advanced Energy Materials

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show abstract

“…The efficient transport of the charge carriers to the respective electrodes is an important prerequisite for a well performing organic solar cell, which is opposed by recombination as crucial loss mechanism limiting the cell performance 2. There are several experimental techniques probing the charge carrier dynamics in organic bulk heterojunction (BHJ) solar cells, for example the transient photovoltage/photocurrent experiment,3, 4 transient absorption spectroscopy5 and the method of time delayed collection field (TDCF) 6–11. However, these experiments offer no direct access to the charge carrier mobility, which is imperative to understand the origin of the charge carrier recombination in organic bulk heterojunction (BHJ) solar cells.…”

Section: Introductionmentioning

confidence: 99%

A New Approach for Probing the Mobility and Lifetime of Photogenerated Charge Carriers in Organic Solar Cells Under Real Operating Conditions

et al. 2012

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A new transient charge extraction technique is presented, which facilitates simultaneous measurements of mobility and lifetime of photogenerated charge carriers in organic solar cells under real operating conditions. An adaptive field control is implemented keeping the solar cell at open circuit conditions during recombination. The practical benefit of the new technique is demonstrated by determining the mobility-lifetime parameter of solar cells based on PCDTBT:PC(71) BM and P3HT:PC(61) BM.

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“…We apply intermittent contact mode atomic force microscopy (IC-AFM), picosecond time-resolved photoluminescence (PL) and transient absorption (TA) spectroscopy to study the impact of DIO on the topography, the nanomorphology and the efficiency of fast photogeneration. Complementary time delayed collection field (TDCF) 24 and open circuit corrected transient charge extraction (OTRACE) 25 measurements yield information about the field dependence of free charge carrier formation and nongeminate recombination dynamics. We find a morphology of the sample processed without DIO characterized by large acceptor agglomerates embedded within an intermixed D-A phase, resulting in a relatively poor PCE.…”

mentioning

confidence: 99%

The Effect of Diiodooctane on the Charge Carrier Generation in Organic Solar Cells Based on the Copolymer PBDTTT-C

Zusan

Gieseking

Zerson

et al. 2015

Sci Rep

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Microstructural changes and the understanding of their effect on photocurrent generation are key aspects for improving the efficiency of organic photovoltaic devices. We analyze the impact of a systematically increased amount of the solvent additive diiodooctane (DIO) on the morphology of PBDTTT-C:PC71BM blends and related changes in free carrier formation and recombination by combining surface imaging, photophysical and charge extraction techniques. We identify agglomerates visible in AFM images of the 0% DIO blend as PC71BM domains embedded in an intermixed matrix phase. With the addition of DIO, a decrease in the size of fullerene domains along with a demixing of the matrix phase appears for 0.6% and 1% DIO. Surprisingly, transient absorption spectroscopy reveals an efficient photogeneration already for the smallest amount of DIO, although the largest efficiency is found for 3% DIO. It is ascribed to a fine-tuning of the blend morphology in terms of the formation of interpenetrating donor and acceptor phases minimizing geminate and nongeminate recombination as indicated by charge extraction experiments. An increase in the DIO content to 10% adversely affects the photovoltaic performance, most probably due to an inefficient free carrier formation and trapping in a less interconnected donor-acceptor network.

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Nongeminate Recombination ofa-Si: H

Cited by 45 publications

References 8 publications

On the Impact of Contact Selectivity and Charge Transport on the Open‐Circuit Voltage of Organic Solar Cells

On the Impact of Contact Selectivity and Charge Transport on the Open‐Circuit Voltage of Organic Solar Cells

A New Approach for Probing the Mobility and Lifetime of Photogenerated Charge Carriers in Organic Solar Cells Under Real Operating Conditions

The Effect of Diiodooctane on the Charge Carrier Generation in Organic Solar Cells Based on the Copolymer PBDTTT-C

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