p-type CuI Films Grown by Iodination of Copper and Their Application As Hole Transporting Layers for Inverted Perovskite Solar Cells

doi:10.15541/jim20150455

Abstract

Abstract:

γ-phase copper iodide (γ-CuI) is a wide bandgap p-type semiconductor with a band gap of 3.1 eV, which is suitable for optoelectronic devices like light-emitting diodes and solar cells. A simple and convenient method of iodination of copper film to prepare CuI film was reported. The effects of iodination time, reaction temperature, and copper/iodine ratio on the transparent and conductive properties of CuI film were explored. CuI films with high transmittance over 75% in the visible range and low resistivity of 4.4×10^-2 Ω·cm were grown under the optimized iodination time (30 min) and iodination temperature (120℃). The CuI films were adopted as hole transporting layers for CuI/CH₃NH₃PbI₃/PCBM inverted planar perovskite solar cell and a maximum photovoltaic efficiency of 8.35% was obtained. The influences of the transparent and conductive properties of CuI films on the solar cell photovoltaic efficiency were also discussed.

Key words: CuI, iodination of copper, transparent and conductive property, inverted perovskite solar cell

CLC Number:

O472

LIU Chang, YUAN Shuai, ZHANG Hai-Liang, CAO Bing-Qiang, WU Li-Li, YIN Long-Wei. p-type CuI Films Grown by Iodination of Copper and Their Application As Hole Transporting Layers for Inverted Perovskite Solar Cells[J]. Journal of Inorganic Materials, 2016, 31(4): 358-364.

Figures/Tables 9

Fig. 1 (a) SEM image and (b) XRD pattern of copper film grown under optimized vacuum thermal deposition condition

Table 1 Growth condition of iodination of copper film

Sample No.	Reaction time/ min	Reaction temperature/℃	Cu/I ratio
1	15	120	1:1
2	30	120	1:1
3	45	120	1:1
4	60	120	1:1
5	30	120	1:1
6	30	140	1:1
7	30	160	1:1
8	30	180	1:1
9	30	140	1:1
10	30	140	1:10
11	30	140	1:100

Fig. 2 SEM images of CuI films deposited with different Cu/I ratios and corresponding XRD patterns and optical transmission spectra (a) 1:1, (b) 1:10, (c) 1:100

Table 2 Hall effect data of CuI films grown with different Cu/I ratios

Cu/I ratio	Resistivity/(10^-2 Ω·cm)	Mobility/(cm²·V^-1·s^-1)
1:1	8.9	8.6
1:10	8.2	13.5
1:100	11.1	1.5

Fig. 3 Surface morphology SEM images of CuI films grown under different iodination temperature and iodination time (a) 15 min, 120℃; (b) 30 min, 120℃; (c) 45 min, 120℃; (d) 30 min, 160℃

Fig. 4 Influence of iodination temperature (a) and iodination time (b) on the transmission property of CuI film with Cu/I ratio of 1:10

Table 3 Hall effect data of CuI films grown under different iodination temperature and time

Iodination time/temperature	Resistivity/ (10^-2 Ω·cm)	Mobility/ (cm²·V^-1·s^-1)
15 min/120℃(Ⅰ)	9.9	14.9
30 min/120℃(Ⅱ)	4.4	29.6
45 min/120℃(Ⅲ)	7.1	17.1
30 min/160℃(Ⅳ)	13.9	9.5

Fig. 5 (a) Schematic diagram and (b) typical SEM image of CuI film based planar perovskite solar cell. (c) Current density-voltage (J-V) characteristic curves and (d) EQE curves of the perovskite solar cells assembled with different CuI films as hole transporting layers. Curves labeled with (I~IV) correspond to samples (I~IV) in Table 3 grown under different iodination temperature and time

Table 4 Corresponding photovoltaic properties of perovskite solar cells (I-IV) with different CuI as hole transporting layer

Devices	V_OC/V	J_SC/(mA·cm^-2)	FF/%	η /%
I	0.92	14.26	53.73	7.05
II	0.93	15.33	58.51	8.35
III	0.89	12.84	54.01	6.17
IV	0.86	8.45	51.70	3.75

References 20

[1]	BÜHERE W, HÄLG W. Crystal structure of high-temperature cuprous iodide and cuprous bromide.International Symposium on Solid Ionic and Ionic-Electronic Conductors, 1977, 22(7): 701-704.
[2]	MIYAKE S, HOSHINO S, TAKENAKA T.On the phase transition in cuprous iodide.Journal of the Physics Society of Japan, 1952, 7(1): 19-24.
[3]	BOUHAFS B, HEIRECHE H, SEKKAL W, et al.Electronic and optical properties of copper halides mixed crystal CuCl1-xIx.Physics Letters A, 1998, 240(4/5): 257-264.
[4]	BÄDEKER K. Über eine eigentümliche Form elektrischen Leitvermögens bei festen Körpern.Annalen der Physik, 1909, 334(8): 566-584.
[5]	SCHEIN F L, VON WENCKSTERN H, GRUNDMANN M. Transparent p-CuI/n-ZnO heterojunction diodes. Applied Physics Letters, 2013, 102(9): 092109-1-4.
[6]	ZHU B L, ZHAO X Z.Transparent conductive CuI thin films prepared by pulsed laser deposition.Phys. Status Solidi A, 2011, 208(1): 91-96.
[7]	ZI M, LI J, ZHANG Z C, et al.Effect of deposition temperature on transparent conductive properties of γ-CuI film prepared by vacuum thermal evaporation.Phys. Status Solidi A, 2015, 212(7): 1466-1470.
[8]	WANG H G, BAI X, WEI J Q, et al.Preparation of CuI particles and their applications in carbon nanotube-Si heterojunction solar cells.Materials Letters, 2012, 79:106-108.
[9]	KUMARA G R A, TISKUMARA J K, RANASINGHE C S K, et al. Efficient solid-state dye-sensitized n-ZnO/D-358 dye/p-CuI solar cell.Electrochimica Acta, 2013, 94: 34-37.
[10]	DAS S, CHOI J Y, ALFORD T L.P3HT:PC61BM based solar cells employing solution processed copper iodide as the hole transport layer.Solar Energy Materials & Solar Cells, 2015, 133: 255-259.
[11]	WANG YAN-XIANG, LUO JUN, GUO PING-CHUN, et al.Application and development of hybrid perovskite materials in the field of solar cells.Journal of Inorganic Materials, 2015, 30(7): 673-682.
[12]	YANG YING, GAO JING, CUI JIA-RUI, et al.Research progress of perovskite solar cell.Journal of Inorganic Materials, 2015, 30(11): 1131-1138.
[13]	YAACOBI-GROSS N, TREAT NEIL D, PATTANASATTAYAVONG P, et al. High-efficiency organic photovoltaic cells based on the solution-processable hole transporting interlayer copper thiocyanate (CuSCN) as a Replacement for PEDOT: PSS. Advanced Energy Materials, 2015, 5(3): 1401529-1-7.
[14]	CHRISTIANS J A, FUNG R C M, KAMAT P V. An inorganic hole conductor for organo-lead halide perovskite solar cells. improved hole conductivity with copper iodide.Journal of American Chemical Society, 2014, 136(2): 758-764.
[15]	SNAITH H J, ABATE A, BALL J M, et al.Anomalous hysteresis in perovskite solar cells.Journal of Physical Chemistry Letters, 2014, 5: 1511-1515.
[16]	CHAVHAN S, MIGUEL O, GRANDE H J, et al.Organo-metal halide perovskite-based solar cells with CuSCN as the inorganic hole selective contact.Journal of Materials Chemistry A, 2014, 2(32): 12754-12760.
[17]	STRANKS S D, EPERON G E, GRANCINI G, et al. Electron- hole diffusion lengths exceeding 1 micrometer in an organometal trihalide perovskite absorber.Science, 342(6156): 341-344.
[18]	KIM H S, PARK N G.Parameters Affecting I-V hysteresis of ch3nh3pbi3 perovskite solar cells: effects of perovskite crystal size and mesoporous tio2 layer.Journal of Physical Chemistry Letter, 2014, 5(17): 2927-2934.
[19]	ZHOU H, CHEN Q, LI G, et al.Interface engineering of highly efficient perovskite solar cells.Science, 2014, 345(6196): 542-546.
[20]	SHI J J, DONG J, LV S T, et al. Hole-conductor-free perovskite organic lead iodide heterojunction thin-film solar cells: High efficiency and junction property. Applied Physics Letter, 2014, 104(6): 063901-1-4.