Effects of Heat Treatment Temperature and Er Doping Amount on Photoelectric Properties of Nickel Oxide Thin Films

doi:10.16553/j.cnki.issn1000-985x.2025.0069

Abstract

Abstract: As a new type of wide band gap hole transport material， NiO has excellent optical and electrical properties. Er doping NiO thin films were prepared by sol-gel method. The effects of annealing temperature and Er doping concentration on the structure and photoelectric properties of NiO thin films were investigated by changing the annealing temperature and Er doping concentration. The results show that crystallinity and visible light transmittance of NiO thin films increase with the increase of annealing temperature from 300 ℃ to 600 ℃， and the resistivity is the lowest at 500 ℃ annealing temperature. With the increase of Er doping concentration from 2% to 10%， the defects of NiO thin films decrease， the grain size increases， and the upconversion luminescence performance increases first and then decreases. The upconversion and electrical properties are the best when the Er doping concentration is 8%. The 8% Er doping NiO film optimized has the highest upconversion luminescence intensity after annealing at 500 ℃ for 2 h. The lowest resistivity is 177.6 Ω·cm and the highest mobility is 0.48 cm²·V^-1·s^-1. This paper successfully provides some theoretical and experimental basis for improving the photoelectric conversion efficiency of perovskite and silicon-based solar cells from two aspects of spectral conversion and hole transport layer material performance optimization.

Key words: NiO thin film; Er doping; sol-gel method; heat treatment; optical property; electrical property

CLC Number:

O484.4

YAO Hanyu, CHEN Kai, YI Yuwei, ZHOU Yanqi, LI Shuang, TANG Quntao. Effects of Heat Treatment Temperature and Er Doping Amount on Photoelectric Properties of Nickel Oxide Thin Films[J]. Journal of Synthetic Crystals, 2025, 54(9): 1622-1632.

Figures/Tables 15

Fig.1 XRD patterns （a） and Raman spectra （b） of NiO thin films at different annealing temperatures

Table 1 XRD diffraction peak data of （200） plane and crystallite sizes calculated by Scherrer formula for NiO samples at different annealing temperatures

Annealing temperature/℃	2θ/（°）	FWHM/（°）	Grain size/nm
300	43.21	0.792	10.39
400	43.19	0.684	12.03
500	43.27	0.532	15.47
600	43.29	0.509	16.16

Fig.2 SEM images of NiO thin films at different annealing temperatures. （a） Sample 1-1；（b） sample 1-2；（c） sample 1-3；（d） sample 1-4；（e） unannealed sample （cross-section image）；（f） sample 1-3 （cross-section image）

Fig.3 Optical transmission curves （a） and optical band gap calculation （b） of pure NiO thin films at different annealing temperatures

Table 2 Test results of resistivity， mobility and free electron concentration of NiO thin films at different annealing temperatures

Annealing temperature/℃	300	400	500	600
Resistivity /（Ω·cm）	585.5	530.5	370.6	433.4
Mobility /（cm²·V^-1·s^-1）	0.13	0.16	0.22	0.15
Carrier concentration/cm^-3	9.8×10¹⁵	2.2×10¹⁶	2.7×10¹⁶	7.6×10¹⁶

Fig.4 XPS spectroscopy of Ni 2p of pure NiO thin films 300 （a） and 500 ℃ （b）

Table 3 Summary of the properties of pure NiO thin films at different annealing temperatures

Sample	Annealing temperature/℃	Grain size/nm	100~800 nmmean transmittance	Optical band gap/eV	Resistivity/（Ω·cm）	Ni³⁺/Ni²⁺
1-1	300	10.39	72.8%	3.68	585.5	1.58
1-2	400	12.03	77.5%	3.62	530.5	—
1-3	500	15.47	79.6%	3.64	370.6	2.71
1-4	600	16.16	81.3%	3.64	433.4	—

Fig.5 XRD patterns of NiO thin films with different Er doping concentrations

Table 4 XRD diffraction peak data of preferred orientation and crystallite sizes calculated by Scherrer formula for NiO samples with different Er doping concentrations

Er doping concentration/%	2θ/（°）	FWHM/（°）	Grain size/nm
2	43.52	0.529	15.57
5	43.48	0.489	16.84
8	37.21	0.502	16.08
10	37.26	0.493	16.37

Fig.6 SEM images of NiO films with different Er doping concentrations

Fig.7 Optical transmission curves （a） and optical band gap calculation （b） of different Er doping concentrations

Fig.8 （a） Up-conversion luminescence spectra of the sample under 980 nm laser irradiation；（b） the up-conversion luminescence intensity enhancement factor of the sample

Table 5 Test results of resistivity， mobility and free electron concentration of NiO thin films of different doping concentrations

Er doping concentration/%	0	2	5	8	10
Resistivity/（Ω·cm）	370.6	274.8	211.5	177.6	243.4
Mobility/（cm²·V^-1·s^-1）	0.22	0.34	0.40	0.48	0.31
Carrier concentration/cm^-3	2.7×10¹⁶	2.1×10¹⁶	3.0×10¹⁶	3.7×10¹⁶	3.9×10¹⁶

Fig.9 XPS of Ni 2p in NiO thin films of different Er doping concentrations. （a） 2%；（b） 5%；（c） 8%；（d） XPS of Er 4d in 2% Er-doped NiO

Table 6 Summary of the properties of pure NiO thin films at different annealing temperatures

Sample	Er doping concentration/%	Grain size/nm	400~800 nm mean transmittance/%	Optical band gap/eV	Resistivity/（Ω·cm）	Upconversion luminescence enhancement factor/（G1/G2/R）	Ni³⁺/Ni²⁺
1-3	0	15.47	79.6	3.64	370.6	—	2.71
2-1	2	15.57	78.9	3.59	274.8	1/1/1	2.88
2-2	5	16.84	80.1	3.62	211.5	1.8/1.5/2	2.97
2-3	8	16.08	82.3	3.64	177.6	12/9/36	3.01
2-4	10	16.37	77.6	3.64	243.4	9/8/23	—

References 35

[1]	ANOOP K M， AHIPA T N. Recent advancements in the hole transporting layers of perovskite solar cells［J］. Solar Energy， 2023， 263： 111937.
[2]	NANDI P， PARK H， SHIN S， et al. NiO as hole transporting layer for inverted perovskite solar cells： a study of X-ray photoelectron spectroscopy［J］. Advanced Materials Interfaces， 2024， 11（8）： 2300751.
[3]	宫联国. 氮掺杂 NiO 薄膜的电化学性质研究［D］. 山西：太原理工大学， 2021.
	GONG L G. Study on the electrochemical properties of nitrogen-doped NiO films ［D］. Shanxi： Taiyuan University of Technology， 2021 （in Chinese）.
[4]	ZHANG C P， WEI K， HU J F， et al. A review on organic hole transport materials for perovskite solar cells： structure， composition and reliability［J］. Materials Today， 2023， 67： 518-547.
[5]	ZHANG S， LU Y R， DING Q J， et al. MOF derived NiO thin film formed p-n heterojunction with BiVO₄ photoelectrode for enhancement of PEC performance［J］. Colloids and Surfaces A： Physicochemical and Engineering Aspects， 2022， 655： 130282.
[6]	朱静怡，丁馨，张晓渝，等. 稀土元素 Er 掺杂提高 WSe₂纳米薄膜的光电特性［J］. 微纳电子技术， 2020， 36（6）： 874-878.
	ZHU J Y， DING X， ZHANG X Y， et al. Rare earth element Er doping improves the photoelectric properties of WSe₂ nanofilms［J］. Micro-nano electronic technology， 2020， 36（6）： 874-878 （in Chinese）.
[7]	胡丹丹. NiO/SiC异质结的制备及其光电特性的研究［D］. 西安：西安理工大学， 2018.
	HU D D. Preparation and photoelectric properties of NiO/SiC heterojunction［D］. Xi'an： Xi'an University of Technology， 2018 （in Chinese）.
[8]	CAI X， HU T， HOU H， et al. A review for nickel oxide hole transport layer and its application in halide perovskite solar cells［J］. Materials Today Sustainability， 2023， 23： 100438.
[9]	ZHANG Y， SONG D P， HUI Z Z， et al. Unexpected large remnant polarization in Sn-doped Bi₄Ti₃O₁₂ ferroelectric film by chemical solution deposition［J］. Journal of Advanced Dielectrics， 2024： 2450027.
[10]	HUANG W H， HE S， HAO A Z， et al. Structural phase transition， electrical and photoluminescent properties of Pr³⁺-doped （1-x）Na_0.5Bi_0.5TiO_3- _x SrTiO₃ lead-free ferroelectric thin films［J］. Journal of the European Ceramic Society， 2018， 38（5）： 2328-2334.
[11]	AZHAR M， NOWSHERWAN G A， IQBAL M A， et al. Morphological， photoluminescence， and electrical measurements of rare-earth metal-doped cadmium sulfide thin films［J］. ACS Omega， 2023， 8（39）： 36321-36332.
[12]	HAUNSBHAVI K， ALAGARASAN D， SHIVARAMU N J， et al. Nanostructured NiO thin film for ammonia sensing at elevated temperatures［J］. Journal of Electronic Materials， 2022， 51（11）： 6356-6368.
[13]	TIMOSHNEV S， KAZAKIN A， SHUBINA K， et al. Annealing temperature effect on the physical properties of NiO thin films grown by DC magnetron sputtering［J］. Advanced Materials Interfaces， 2024， 11（9）： 2300815.
[14]	WEI H M， WU Y Q. Study on the up-conversion luminescence and conductivity behavior of p-type NiO:Yb， Er thin films［J］. Materials， 2023， 16（13）： 4637.
[15]	符文迪. NiO 基透明 pn 结的制备及其光电效应的研究［D］. 浙江：浙江理工大学， 2022．
	FU W D. Preparation of NiO-based transparent pn junction and its photoelectric effect［D］. Zhejiang： Zhejiang University of Technology， 2022 （in Chinese）.
[16]	王　新，谭封印，丛凡超，等. Mg掺杂对NiO基薄膜能带调控作用［J］. 吉林师范大学学报（自然科学版）， 2023， 44（3）： 11-17.
	WANG X， TAN F Y， CONG F C， et al. The regulatory effect of Mg-doping on the energy band of NiO based thin films［J］. Journal of Jilin Normal University （Natural Science Edition）， 2023， 44（3）： 11-17 （in Chinese）.
[17]	AUZEL F. Upconversion and anti-Stokes processes with f and d ions in solids［J］. Chemical Reviews， 2004， 104（1）： 139-173. DOI PMID
[18]	于晓晨，李华健，高博扬，等. Er³⁺/Yb³⁺共掺杂Ca_0.5Gd（WO₄）₂荧光粉的发光性能和温度特性［J］. 材料导报， 2022， 36 （18）： 21050128-6.
	YU X C， LI H J， GAO B Y， et al. Luminescence properties and temperature characteristics of Er³⁺/Yb³⁺ co-doped Ca_0.5Gd（WO₄）₂ phosphors［J］. Material introduction， 2022， 36（18）： 21050128-6 （in Chinese）.
[19]	ZHANG C， SHI Y L， LU K L， et al. Ultrapure single-band red upconversion luminescence in Er³⁺ doped sensitizer-rich ytterbium oxide transparent ceramics for solid-state lighting and temperature sensing［J］. Optics Express， 2023， 31（18）： 28963-28978.
[20]	ANANTHI S， KAVITHA M， BALAMURUGAN A， et al. Synthesis， analysis and characterization of camellia sinensis mediated synthesis of NiO nanoparticles for ethanol gas sensor applications［J］. Sensors and Actuators B： Chemical， 2023， 387： 133742.
[21]	FELDL J， BUDDE M， TSCHAMMER C， et al. Magnetic characteristics of epitaxial NiO films studied by Raman spectroscopy［J］. Journal of Applied Physics， 2020， 127（23）： 235105.
[22]	PURUSHOTHAMAN K K， MURALIDHARAN G. The effect of annealing temperature on the electrochromic properties of nanostructured NiO films［J］. Solar Energy Materials and Solar Cells， 2009， 93（8）： 1195-1201.
[23]	罗启仁，刘昌，吴昊. ALD法制备Li掺杂NiO _x 作为HTL提升PSC性能［J］. 半导体技术， 2024， 49 （10）： 885-892+898.
	LUO Q R， LIU C， WU H. ALD method to prepare Li-doped NiO _x as HTL to improve PSC performance［J］. Semiconductor technology， 2024， 49（10）： 885-892+898 （in Chinese）.
[24]	ALIDOUST N， TOROKER M C， KEITH J A， et al. Significant reduction in NiO band gap upon formation of Li _x Ni_1- _x O alloys： applications to solar energy conversion［J］. ChemSusChem， 2014， 7（1）： 195-201.
[25]	OSORIO-GUILLÉN J， LANY S， BARABASH S V， et al. Nonstoichiometry as a source of magnetism in otherwise nonmagnetic oxides： magnetically interacting cation vacancies and their percolation［J］. Physical Review B， 2007， 75（18）： 184421.
[26]	NANDY S， SAHA B， MITRA M K， et al. Effect of oxygen partial pressure on the electrical and optical properties of highly （200） oriented p-type Ni_1- _x O films by DC sputtering［J］. Journal of Materials Science， 2007， 42（14）： 5766-5772.
[27]	KIM K S， WINOGRAD N. X-ray photoelectron spectroscopic studies of nickel-oxygen surfaces using oxygen and argon ion-bombardment［J］. Surface Science， 1974， 43（2）： 625-643.
[28]	RATCLIFF E L， MEYER J， STEIRER K X， et al. Evidence for near-surface NiOOH species in solution-processed NiO _x selective interlayer materials： impact on energetics and the performance of polymer bulk heterojunction photovoltaics［J］. Chemistry of Materials， 2011， 23（22）： 4988-5000.
[29]	BOUKHARI JAL， KHALAF A， SAYED HASSAN R， et al. Structural， optical and magnetic properties of pure and rare earth-doped NiO nanoparticles［J］. Applied Physics A， 2020， 126（5）： 323.
[30]	GAO C Y， LI Z C， PENG D C， et al. Comparative investigation of the effect of rare earth elements （Y， Sm and La） in NiO-based NTC thermistors with high temperature sensitivity［J］. Surfaces and Interfaces， 2024， 55： 105398.
[31]	HAUNSBHAVI K， KUMAR K D A， UBAIDULLAH M， et al. The effect of rare-earth element （Gd， Nd， La） doping of NiO films on UV photodetector［J］. Physica Scripta， 2022， 97（5）： 055815.
[32]	VETRONE F， BOYER J C， CAPOBIANCO J A， et al. Concentration-dependent near-infrared to visible upconversion in nanocrystalline and bulk Y₂O₃:Er³⁺ ［J］. Chemistry of Materials， 2003， 15（14）： 2737-2743.
[33]	VETRONE F， BOYER J C， CAPOBIANCO J A， et al. NIR to visible upconversion in nanocrystalline and bulk Lu₂O₃:Er³⁺ ［J］. The Journal of Physical Chemistry B， 2002， 106（22）： 5622-5628.
[34]	CHEN X F， XU L， CHEN C， et al. Rare earth ions doped NiO _x hole transport layer for efficient and stable inverted perovskite solar cells［J］. Journal of Power Sources， 2019， 444： 227267.
[35]	ZHANG K H L， XI K， BLAMIRE M G， et al. P-type transparent conducting oxides［J］. Journal of Physics Condensed Matter， 2016， 28（38）： 383002.