Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current

doi:10.1007/s11705-020-1976-z

Front. Chem. Sci. Eng.

2021, Vol. 15

Issue (1) : 164-179 https://doi.org/10.1007/s11705-020-1976-z

RESEARCH ARTICLE

Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current

Boa Jin¹, Hyunmin Park¹, Yang Liu², Leijing Liu², Jongdeok An¹, Wenjing Tian², Chan Im¹(

)

¹. Department of Chemistry, Konkuk University, Seoul 05029, Republic of Korea
². State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China

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Abstract

To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells, the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages, and a wide range of excitation intensities are analyzed. For this purpose, conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used. After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current, the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility. By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers, the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained. Subsequently, the charge-carrier concentration-dependent mobility values were obtained, and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.

Keywords charge-carrier photogeneration transient photocurrent polymer solar cells charge-carrier extraction space charge-limited current

Corresponding Author(s): Chan Im

Just Accepted Date: 25 September 2020 Online First Date: 17 December 2020 Issue Date: 12 January 2021

Cite this article:

Boa Jin,Hyunmin Park,Yang Liu, et al. Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime of the space charge-limited current[J]. Front. Chem. Sci. Eng., 2021, 15(1): 164-179.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-020-1976-z
https://academic.hep.com.cn/fcse/EN/Y2021/V15/I1/164

Fig.1 TPC traces of the following devices at the 0 V external-bias voltage with various excitation intensities: (a) PTB7:PC71BM and (b) P3HT:PCBM (Dash lines are demonstrative extrapolating lines that are based on the tangents of the fast exponential-decay parts of the TPC traces of the cases with the highest incident photon densities. These lines were slightly moved to the upside for an improved readability). Inset in the (a), the post-correction maximum photocurrent density at the initial peak is plotted as a function of the incident photon density. The solid lines with a slope of 1 are shown for the eye-guiding purpose.

Fig.2 Dark J?V plots of PTB7 (solid line with rectangles) and P3HT (solid line with open rectangles), and the maximum photocurrent density at the initial peak vs. voltage (V_total) plots of PTB7 (dash line with rectangles) and P3HT (dash line with open rectangles). In the inset, the same dark J?V plots are shown at a linear scale. An additional solid line with a slope of 1 is shown for the eye-guiding purpose.

Tab.1 Overview of the bias convention used in this study

Fig.3 (a) Numbers of the extracted CCs, as calculated from the integration of the TPC traces; (b) the EQE; (c) the ExtQE, as functions of the incident photon density. The solid lines with slopes of 1 and 0.67 are shown for the eye-guiding purpose.

Fig.4 Schema to compare the EQEs and the IQEs under the ss and TPC conditions of the PTB7 case.

Fig.5 Normalized TPC traces of PTB7 at (a) 0.4 V, (b) 0 V, and (c) –2 V, and those of P3HT at (d) 0.4 V, (e) 0 V, and (f) –2 V. The dash-dot lines in (a), (b), (d) and (e) are the calculated RC decays with the 0.45 ms time constant, while the dot lines in (c) and (f) are the experimentally estimated dark charging curves. The dot lines at the initial parts are the eye-guiding lines for the slopes of the first parts of the TPC traces.

Tab.2 Average time constants (t) of the first-decay parts

Fig.6 Plots of (a) t_1/e vs. the incident photon density and (b) t_1/e.2nd vs. the incident photon density. The horizontal dash lines mark the RC time constant of the used device of this study.

Fig.7 Magnification of normalized TPC traces at the following external biases at linear scales: (a) 0.4 V; (b) 0 V; (c) –2 V. The dash lines are the calculated RC decay curves.

Fig.8 Plots of the CC mobility vs. the incident photon density. (a) Native t_1/e CC mobility; (b) CC mobility corrected by the RC-time-constant effect; (c) CC mobility corrected by the RC time constant and the saturation effect. The calculated CC mobilities for which an RC time of 0.45 ms was used at the external biases of 0.4 V (straight line), 0 V (dash line), and –2 V (dot line) are marked in (a). The points marked with arrows in (b) are for the assignment of the CC mobilities that were significantly affected by the RC time.

Fig.9 Two-dimensional energy-level maps of the active layers with the corresponding density of states: (a) for a high electric field and (b) for a low electric field.

1	F C Krebs, N Espinosa, M Hösel, R R Søndergaard, M Jørgensen. Rise to power—OPV-based solar parks. Advanced Materials, 2014, 26(1): 29–39 https://doi.org/10.1002/adma.201302031
2	K Jiang, Q Wei, J Y L Lai, Z Peng, H K Kim, J Yuan, L Ye, H Ade, Y Zou, H Yan. Alkyl Chain tuning of small molecule acceptors for efficient organic solar cells. Joule, 2019, 3(19): 3020–3033 https://doi.org/10.1016/j.joule.2019.09.010
3	Y Lin, B Adilbekova, Y Firdaus, E Yengel, H Faber, M Sajjad, X Zheng, E Yarali, A Seitkhan, O M Bakr, A El-Labban, U Schwingenschlögl, V Tung, I McCulloch, F Laquai, T D Anthopoulos. 17% efficient organic solar cells based on liquid exfoliated WS2 as a replacement for PEDOT:PSS. Advanced Materials, 2019, 31(46): 1902965–1902965 https://doi.org/10.1002/adma.201902965
4	W S Yang, B W Park, E H Jung, N J Jeon, Y C Kim, D U Lee, S S Shin, J Seo, E K Kim, J H Noh, S I Seok. Iodide management in formamidinium-lead-halide–based perovskite layers for efficient solar cells. Science, 2017, 356(6345): 1376–1379 https://doi.org/10.1126/science.aan2301
5	M A Green. The path to 25% silicon solar cell efficiency: history of silicon cell evolution. Progress in Photovoltaics: Research and Applications, 2009, 17(3): 183–189 https://doi.org/10.1002/pip.892
6	L Torto, A Cester, A Rizzo, N Wrachien, S A Gevorgyan, M Corazza, F C Krebs. Model of organic solar cell photocurrent including the effect of charge accumulation at interfaces and non-uniform carrier generation. Journal of Electron Devices Society, 2016, 4(6): 387–395 https://doi.org/10.1109/JEDS.2016.2602563
7	S M Menke, N A Ran, G C Bazan, R H Friend. Understanding energy loss in organic solar cells: toward a new efficiency regime. Joule, 2018, 2(1): 25–35 https://doi.org/10.1016/j.joule.2017.09.020
8	H Park, J An, J Song, M Lee, H Ahn, M Jahnel, C Im. Thickness-dependent internal quantum efficiency of narrow band-gap polymer-based solar cells. Solar Energy Materials and Solar Cells, 2015, 143: 242–249 https://doi.org/10.1016/j.solmat.2015.07.002
9	J Moulé, J B Bonekamp, K Meerholz. The effect of active layer thickness and composition on the performance of bulk-heterojunction solar cells. Journal of Applied Physics, 2006, 100(9): 094503-1, 094503–094507 https://doi.org/10.1063/1.2360780
10	J Song, Y Lee, B Jin, J An, H Park, H Park, M Lee, C Im. Connecting charge transfer kinetics to device parameters of a narrow band-gap polymer-based solar cell. Physical Chemistry Chemical Physics, 2016, 18(38): 26550–26561 https://doi.org/10.1039/C6CP04688F
11	U B Cappel, S M Feldt, J Schöneboom, A Hagfeldt, G Boschloo. The influence of local electric fields on photo-induced absorption in dye sensitized solar cells. Journal of the American Chemical Society, 2010, 132(26): 9096–9101 https://doi.org/10.1021/ja102334h
12	A Pivrikas, N S Sariciftci, G Juska, R Österbacka. A review of charge transport and recombination in polymer/fullerene organic solar cells. Progress in Photovoltaics: Research and Applications, 2007, 15(8): 677–696 https://doi.org/10.1002/pip.791
13	Y Gao, A Pivrikas, B Xu, Y Liu, W Xu, P H M van Loosdrecht, W Tian. Measuring electron and hole mobilities: charge selective CELIV. Synthetic Metals, 2015, 203: 187–191 https://doi.org/10.1016/j.synthmet.2015.02.036
14	H Park, B Jin, Y Kim, C Im, J An, H Park, W Tian. Intensity-dependent transient photocurrent of organic bulk heterojunction solar cells. Journal of the Korean Physical Society, 2017, 70(2): 177–183 https://doi.org/10.3938/jkps.70.177
15	C Im, H Bässler, H Rost, H H Hörhold. Hole transport in polyphenylenevinylene-ether under bulk photoexcitation and sensitized injection. Journal of Chemical Physics, 2000, 113(9): 3802–3807 https://doi.org/10.1063/1.1287657
16	H Bässler, A Köhler. Unimolecular and supramolecular electronics: charge transport in organic semiconductors. Topics in Current Chemistry, 2012, 312: 1–65
17	I A Howard, J M Hodgkiss, X Zhang, K R Kirov, H A Bronstein, C K Williams, R H Friend, S Westenhoff, N C Greenham. Charge recombination and exciton annihilation reactions in conjugated polymer blends. Journal of the American Chemical Society, 2010, 132(1): 328–335 https://doi.org/10.1021/ja908046h
18	D Di Nuzzo, S van Reenen, R A J Janssen, M Kemerink, S C J Meskers. Evidence for space charge-limited conduction in organic photovoltaic cells at open-circuit conditions. Physical Review. B, 2013, 87(8): 085207-1, 085207–085211 https://doi.org/10.1103/PhysRevB.87.085207
19	S R Cowan, N Banerji, W L Leong, A J Heeger. Charge formation, recombination, and sweep-out dynamics in organic solar cells. Advanced Functional Materials, 2012, 22(6): 1116–1128 https://doi.org/10.1002/adfm.201101632
20	I Hwang, N C Greenham. Modeling photocurrent transients in organic solar cells. Nanotechnology, 2008, 19(42): 424012 https://doi.org/10.1088/0957-4484/19/42/424012
21	D Credgington, J R Durrant. Insights from transient optoelectronic analyses on the open-circuit voltage of organic solar cells. Journal of Physical Chemistry Letters, 2012, 3(11): 1465–1478 https://doi.org/10.1021/jz300293q
22	K Sudheendra Rao, Y N Mohapatra. Open-circuit voltage decay transients and recombination in bulk-heterojunction solar cells. Applied Physics Letters, 2014, 104(20): 203303 https://doi.org/10.1063/1.4879278
23	M Miyake, H Nakajima, A Hemmi, M Yahiro, C Adachi, N Soh, R Ishimatsu, K Nakano, K Uchiyama, T Imato. Performance of an organic photodiode as an optical detector and its application to fluorometric flow-immunoassay for IgA. Talanta, 2012, 96: 132–139 https://doi.org/10.1016/j.talanta.2012.02.006
24	M Jahnel, M Thomschke, K Fehse, U Vogel, J D An, H Park, K Leo, C Im. Integration of near IR and visible organic photodiodes on a complementary metaloxidesemi-conductor compatible backplane. Thin Solid Films, 2015, 592(Part A): 94–98
25	G Jŭska, K Genevǐcius, N Nekrǎsas, G Sliaŭzys. Charge carrier transport, recombination, and trapping in organic solar cells studied by double injection technique. IEEE Journal of Selected Topics in Quantum Electronics, 2010, 16(6): 1764–1769 https://doi.org/10.1109/JSTQE.2010.2041752
26	C R McNeill, I Hwang, N C Greenham. Polaronic interaction of photocurrent transients in all-polymer solar cells: trapping and detrapping effects. Journal of Applied Physics, 2006, 106: 024507-1–024507-8
27	T Hahn, S Tscheuschner, F J Kahle, M Reichenberger, S Athanasopoulos, C Saller, G C Bazan, T Q Nguyen, P Strohriegl, H Bässler, A Köhler. Monomolecular and bimolecular recombination of electronhole pairs at the interface of a bilayer organic solar cell. Advanced Functional Materials, 2017, 27(1): 1604906 https://doi.org/10.1002/adfm.201604906
28	S Valouch, M Nintz, S W Kettlitz, N S Christ, U Lemmer. Thickness-dependent transient photocurrent response of organic photodiodes. IEEE Photonics Technology Letters, 2012, 24(7): 596–598 https://doi.org/10.1109/LPT.2012.2184276
29	K Kniepert, D Neher. Effect of the RC time on photocurrent transients and determination of charge carrier mobilities. Journal of Applied Physics, 2017, 122(19): 195501 https://doi.org/10.1063/1.4999278
30	S W Kettlitz, J Mescher, N S Christ, M Nintz, S Valouch, A Colsmann, U Lemmer. Eliminating RC-effects in transient photocurrent measurements on organic photodiodes. IEEE Photonics Technology Letters, 2013, 25(7): 682–685 https://doi.org/10.1109/LPT.2013.2247036
31	D Zhang, A Allagui, A S Elwakil, A M Nassef, H Rezk, J Cheng, W C H Choy. On the modeling of dispersive transient photocurrent response of organic solar cells. Organic Electronics, 2019, 70: 42–47 https://doi.org/10.1016/j.orgel.2019.03.054
32	H Bässler. Charge transport in disordered organic photoconductors a Monte Carlo simulation study. Physica Status Solidi. B, Basic Research, 1993, 175(1): 15–56 https://doi.org/10.1002/pssb.2221750102
33	S K Gupta, A Sharma, S Banerjee, R Gahlot, N Aggarwal, Deepak, A Garg. Understanding the role of thickness and morphology of the constituent layers on the performance of inverted organic solar cells. Solar Energy Materials and Solar Cells, 2013, 116: 135–143 https://doi.org/10.1016/j.solmat.2013.03.027
34	F Liu, W Zhao, J R Tumbleston, C Wang, Y Gu, D Wang, A L Briseno, H Ade, T P Russell. Understanding the morphology of PTB7∙PCBM blends in organic photovoltaics. Advanced Energy Materials, 2014, 4(5): 1301377 https://doi.org/10.1002/aenm.201301377
35	C Longeaud, C Main. Deconvolution of the transient photocurrent signals: application to the study of the density of states of a BTO crystal. Journal of Physics Condensed Matter, 2008, 20(13): 135217 https://doi.org/10.1088/0953-8984/20/13/135217

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