Heterojunction Organic Photovoltaic Cells as Molecular Heat Engines: A Simple Model for the Performance Analysis

Einax, Mario; Dierl, Marcel; Nitzan, Abraham

doi:10.1021/jp205856x

Cited by 38 publications

(80 citation statements)

References 23 publications

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“…[2][3][4][5][6][7][8][9] Some other approaches have also been developed to study the efficiency, in particular, on the basis of a thermodynamic detailed balance. [10][11][12][13][14] As a practical approach, limits for solar cells were assessed using criteria based on the short circuit currents, open circuit voltage and other quantities.…”

Section: Introductionmentioning

confidence: 99%

Theoretical limit of power conversion efficiency for organic and hybrid halide perovskite photovoltaics

Seki

Furube

Yoshida

2015

Jpn. J. Appl. Phys.

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We calculated the maximum power conversion efficiency as a function of the optical band gap for organic photovoltaic (PV) cells by assuming that charge separation is accompanied by the energy loss required to dissociate strongly bound charge pairs. The dissociation energy can be estimated from the relationship between the open circuit voltage (V OC ) and the optical band gap (E g ). By analyzing the published data on V OC and E g , the dissociation energy can be estimated. The result could be used as a guide for selecting donor and acceptor materials. We also studied the theoretical limit of power conversion efficiency of hybrid halide perovskite by taking into account the energy loss involved in the carrier transfer from the perovskite phase to the metal oxide charge transport layer.

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Section: Introductionmentioning

confidence: 99%

Theoretical limit of power conversion efficiency for organic and hybrid halide perovskite photovoltaics

Seki

Furube

Yoshida

2015

Jpn. J. Appl. Phys.

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“…Understanding the relationship between system properties that affect exciton dissociation at the D-A interface and consequently U oc is subject of active research [9,19,20]. To study how nonradiative losses at the D-A interface influence the overall device performance, we invoke the minimal model used in our previous publication [21], a solar cell with coupled donor and acceptor molecules, each described as a two-level (HOMO, LUMO) system, in contact with two electrodes, L and R (see Fig. 1).…”

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confidence: 99%

Multiple state representation scheme for organic bulk heterojunction solar cells: A novel analysis perspective

Einax¹,

Dierl²,

Schiff³

et al. 2013

EPL

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Abstract. -The physics of organic bulk heterojunction solar cells is studied within a six state model, which is used to analyze the factors that affect current-voltage characteristics, powervoltage properties and efficiency, and their dependence on nonradiative losses, reorganization of the nuclear environment, and environmental polarization. Both environmental reorganization and polarity is explicitly taken into account by incorporating Marcus heterogeneous and homogeneous electron transfer rates. The environmental polarity is found to have a non-negligible influence both on the stationary current and on the overall solar cell performance. For our organic bulk heterojunction solar cell operating under steady-state open circuit condition, we also find that the open circuit voltage logarithmically decreases with increasing nonradiative electron-hole recombination processes.Considerable progress has been achieved in improving the device efficiency of bulk heterojunction (BHJ) organic solar cells, with a recently set record of 10.7%. [1,2] Much of this success came about by searching for promising electron-donor polymers characterized by low optical gap, using fullerene based electron-acceptor derivatives and optimizing the interpenetrated frozen-in microstructures. Such phase-separated blend morphologies are distinguished by a large interface area between the donor and the acceptor phases, which is a prerequisite to tailor most efficient organic photovoltaic solar cells (OPVs). While material design is one successful strategy to improve the OPV setup, another is to focus on the device physics by developing approaches that take into account physical and chemical features of BHJ organic solar cells in order to improve their dynamical operation. In the last two years there appeared several reviews [3][4][5][6][7] and perspective articles [8, 9] about both material designs and device physics giving an excellent account of the state-of-the-art for organic photovoltaics.In the context of solar energy conversion, device physics aims to identify routes for improved cell performance by studying models that account for both the material prop-(a) E-mail: meinax@uos.de erties and the underlying microscopic principles of the energy conversion processes, i. e. structural and energetics system parameters, in order to identify critical factors that affect the overall OPV performance. Thus, the generated free carriers in a photovoltaic device, which can be harvested at the electrodes, are limited by the complex interplay between charge generation, diffusion, and recombination processes. In BHJ organic solar cells the generation of free charge carriers requires that photoinduced excitons (bounded electron-hole pairs) on the donor material must diffuse to and dissociate at the donor-acceptor (D-A) interface before their recombination takes place. This exciton dissociation at the D-A interface starts with the formation of a charge transfer (CT) state (a geminate pair), where the hole and the electron remain at close proximity on thei...

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“…We previously discussed a similar model [58,59] in a study of the quantum coherence effects on electron transport in DBA junctions. Einax et al [42,44] utilized the model in consideration of a molecular heat engine within a hopping transport regime. Here, we elucidate the effects of intra-molecular quantum coherence (Rabi oscillation between the LUMOs, levels 2 and 3; see Figure 1) on the thermodynamic performance of the engine.…”

Section: Modelmentioning

confidence: 99%

“…This setup is a simple model for a continuous steady-state heat engine [55][56][57], whose thermoelectric efficiency was previously considered in [41,42,44] with the effects of quantum coherence disregarded. The latter were shown to play an important role in the charge and energy transport in similar models of DBA molecular junctions [58,59].…”

Section: Introductionmentioning

confidence: 99%

Molecular Heat Engines: Quantum Coherence Effects

Chen

Gao

Galperin

2017

Entropy

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Recent developments in nanoscale experimental techniques made it possible to utilize single molecule junctions as devices for electronics and energy transfer with quantum coherence playing an important role in their thermoelectric characteristics. Theoretical studies on the efficiency of nanoscale devices usually employ rate (Pauli) equations, which do not account for quantum coherence. Therefore, the question whether quantum coherence could improve the efficiency of a molecular device cannot be fully addressed within such considerations. Here, we employ a nonequilibrium Green function approach to study the effects of quantum coherence and dephasing on the thermoelectric performance of molecular heat engines. Within a generic bichromophoric donor-bridge-acceptor junction model, we show that quantum coherence may increase efficiency compared to quasi-classical (rate equation) predictions and that pure dephasing and dissipation destroy this effect.

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Heterojunction Organic Photovoltaic Cells as Molecular Heat Engines: A Simple Model for the Performance Analysis

Cited by 38 publications

References 23 publications

Theoretical limit of power conversion efficiency for organic and hybrid halide perovskite photovoltaics

Theoretical limit of power conversion efficiency for organic and hybrid halide perovskite photovoltaics

Multiple state representation scheme for organic bulk heterojunction solar cells: A novel analysis perspective

Molecular Heat Engines: Quantum Coherence Effects

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