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제126회 대한화학회 학술발표회 및 총회 Internal Quantum Efficiency of Solar Cells with Organic and Quantum Dot Absorbers through Optical Simulation

2020년 9월 10일 21시 42분 13초
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화 16시 : 00분
Materials Chemistry - Recent Trend in Next-Generation Optoelectronics
저자 및
Hyeok Kim
University of Seoul, Korea
The internal quantum efficiency (IQE) of a solar cell is the ratio of the number of charge carriers extracted from the cell to the number of photons absorbed in the active layer of the solar cell. The IQE value of a solar cell can provide us useful information about electrical properties of the solar cell because IQE measurements normalize the current generation efficiency by photon generation efficiency and separates the electrical properties from optical properties of the solar cells. In a solar cell the magnitude of the IQE is inversely proportional to the probability of charge carrier recombination in the cell. The wavelength dependent IQE spectra of a solar cell can also provide information about exciton harvesting efficiency of the cell and spatial dependence of charge recombination [1]. Presence of many other interesting effects such as multiple exciton generation, singlet exciton fission, and bias-dependent photoconductivity within a solar cell can also be detected by measuring IQEs greater than 100% [2-3]. Despite its usefulness as a characterization tool, IQE is rarely reported due to the unavailability of its estimation method. For the accurate estimation of IQE value of a solar cell, we need to utilize the absorption spectra of active layer of the cell. The active layer exists within the cell so it is not possible to record the absorption spectra of the active layer of the solar cell directly [4]. When IQE is reported, absorption is frequently not measured in actual devices; this can lead to errors since reflective electrodes induce strong interference effects that substantially affect absorption. When absorption is measured in actual devices, parasitic absorptions are almost never taken into account. Therefore, here, we have utilized optical simulation as a tool to estimate the absorption spectra of the active layer of different solar cells (organic and quantum dot) more precisely. To describe the optical properties of different layers of those solar cells we have incorporated frequency dependent refractive index (n) and extinction coefficient (k) values of those layers in the software interface. Afterwards, we have used the estimated absorption spectra of active layers of different solar cells and experimentally measured external quantum efficiency (EQE) of those cells to estimate their IQE spectra. We believe that this straightforward method of measuring IQE will help the community to understand the underlying mechanism behind high performance solar cells. References 1. G. F. Burkhard, E. T. Hoke, M. D. McGehee, Nano Lett. 9, 4037 (2009). 2. R. D. Schaller, V. I. Klimov, Phys. Rev. Lett. 92, 186601 (2004). 3. A. J. Nozik, Physica E. 14, 115 (2002). 4. M. Law et al., Nano Letters. 8(11), 3904 (2008).