Supplementary Material

Device Architecture Engineering in Polymer/ZnO Quantum Dots/ZnO Array Ternary Hybrid Solar Cells

Fan Wu,*a Yu Zhao,b Hui Zhang,c Yanhua Tongd

a School of Science and Key Lab of Optoelectronic Materials and Devices, Huzhou University, Huzhou, 313000, People’s Republic of China;

b Huzhou Center of New Energy Industrial Innovation, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Huzhou 313000, People’s Republic of China;

c Department of Technology, Beijing Aerospace Wanfang Technology Co., Ltd, Beijing, 100070, People’s Republic of China

d Department of Material Science and Engineering, Huzhou University, Huzhou, 313000, People’s Republic of China

Fig. S1. Room temperature PL spectra of pristine ZnO-NRA and ZnO-CSA.

The pristine ZnO-NRA and ZnO-CSA are characterized by photoluminescence (PL) spectra. The ZnO nanorod array sample normally exhibits a near band edge (NBE) emission at 382 nm and a broad emission peak at 500−600 nm.1,2 In addition, an emission at 366 nm is observed which has been recognized as the NBE emission of ZnO-QDs with a size less than 5 nm.3 The appearance of the NBE peak at 366 nm confirms the formation of shell consisting of ZnO-QDs.

Fig. S2. The J–V characteristics of the devices A-III (a) and A-IV (b) with different blend ratios of MEH-PPV:ZnO-QDs.

The photovoltaic performances of HSCs in device A-III and A-IV with different blend ratios of MEH-PPV:ZnO-QDs from 1:0.5 to 1:1.5 were investigated. When the MEH-PPV:ZnO-QDs blend ratios varied from 1:0.5 to 1:1 in device A-III and A-IV, there was an obvious increase in Jsc; because of the short dffusion length of excitons in MEH-PPV (∼5−8 nm),4 the excitons only within the diffusion length can lead to free charge carriers. The increased Jsc should be originated from the significantly increased interfacial area for exciton dissociation by incorporating ZnO-QDs. When the MEH-PPV:ZnO-QDs blend ratio equals to 1:1.5, the Jsc and Voc were both decreased in device A-III and A-IV. The Jsc in device A-III and A-IV by incorporating ZnO-QDs in polymer will be a competitive result of increased interfacial area for exciton dissociation and decreased polymer amount infiltrated into nanorod interspaces.5,6 The decrease of device performance with MEH-PPV:ZnO-QDs blend ratio of 1:1.5 should be attributed to the reduced the amount of MEH-PPV between the nanorods 5,6 due to the high concentration of ZnO-QDs.

References:

[1] H. Usui, “Influence of surfactant micelles on morphology and photoluminescence of zinc oxide nanorods prepared by one-step chemical synthesis in aqueous solution,” J. Phys. Chem. C, vol. 111, no. 26, pp. 9060–9065, Jun. 2007.

[2] D. C. Olson, S. E. Shaheen, R.T. Collins, and D. S. Ginley, “The effect of atmosphere and ZnO morphology on the performance of hybrid poly(3-hexylthiophene)/ZnO nanofiber photovoltaic devices,” J. Phys. Chem. C, vol. 111, no. 44, pp. 16670–16678, Oct. 2007.

[3] Y. Liu, T. Morishima,T. Yatsui, T. Kawazoe, and M. Ohtsu, “Size control of sol–gel-synthesized ZnO quantum dots using photo-induced desorption,” Nanotechnology, vol. 22, no. 21, pp. 215605, May. 2011.

[4] D. E. Markov, C. Tanase, P. W. M. Blom, and J. Wildeman, “Simultaneous enhancement of charge transport and exciton diffusion in poly(p-phenylene vinylene) derivatives,” Phys.Rev. B, vol. 72, no. 4, pp. 045217, Jul. 2005.

[5] F. Wu, Q. Cui, Z. Qiu, C. Liu, H. Zhang, W. Shen, and M. Wang, “Improved open-circuit voltage in polymer/oxide-nanoarray hybrid solar cells by formation of homogeneous metal oxide core/shell structures,” ACS Appl. Mater. Interfaces, vol. 5, no. 8, pp. 3246–3254, Apr. 2013.

[6] L. E. Greene, M. Law, B. D. Yuhas, and P. Yang, “ZnO-TiO2 core-shell nanorod/P3HT solar cells,” J. Phys. Chem. C, vol. 111, no. 50, pp. 18451–18456, Nov. 2007.

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