Research Progress of Inorganic Hole Transport Materials in Perovskite Solar Cells

doi:10.15541/jim20230105

Abstract

Abstract:

Organic-inorganic hybrid perovskite solar cells (PSCs) have attracted widespread attention due to their high power conversion efficiency (PCE) and low manufacturing cost. Although the certified PCE has reached 25.8%, the stability of PSCs under high temperature, high humidity, and continuous light exposure is still significantly inferior to that of traditional cells, which hinders their commercialization. Developing and applying highly stable inorganic hole transport materials (HTMs) is currently one of the effective methods to solve the photo-thermal stability of devices, which can effectively shield water and oxygen from corroding the perovskite absorption layer, thereby avoiding the formation of ion migration channels. This paper outlines the approximate classification and photoelectric properties of inorganic HTMs, introduces relevant research progress, summarizes performance optimization strategies for inorganic HTMs devices, including element doping, additive engineering, and interface engineering, and finally prospects the future development directions. It is necessary to further study the microstructure of inorganic HTMs and their relationship with the performance of PSCs to achieve more efficient and stable PSCs.

Key words: inorganic hole transport materials, perovskite solar cells, stability, power conversion efficiency, review

CLC Number:

TQ174

CHEN Yu, LIN Puan, CAI Bing, ZHANG Wenhua. Research Progress of Inorganic Hole Transport Materials in Perovskite Solar Cells[J]. Journal of Inorganic Materials, 2023, 38(9): 991-1004.

Figures/Tables 9

Fig. 1 (a) Formal (n-i-p) structure and (b) inverted (p-i-n) structure

Table 1 Properties of inorganic hole transport materials (Spiro-OMeTAD for comparison)

Material	Hole concentration, N/cm^-3	Hole mobility, μ/(cm²·V^-1·s^-1)	Conductivity, σ/(S·cm^-1)
Sprio-OMeTAD with Li-TFSI, etc.	7.13×10^15[19]	0.779^[19]	1.53×10^-3[13]
NiO	5.3×10^18[20]	0.12^[20]	1.66×10^-4[21]
Cu:NiO	7.3×10^19[22]	~0.2^[22]	1.25×10^-3[23]
Ni_0.8Li_0.05Mg_0.15O	6.46×10^18[24]	-	2.23×10^-3[24]
CuGaO₂	3.098×10^19[25]	-	4.625×10^-3[25]
Zn:CuGaO₂	1.328×10^20[25]	-	1.39×10^-2[25]
CuCrO₂	-	0.1-1.0^[26]	2.9×10^-2[27]
In:CuCrO₂	7.1×10^18[27]	0.75^[27]	6.9×10^-2[27]
CuScO₂	-	-	2.11×10^-3[28]
CuSCN	-	1.2×10^-3[21]	-
Co₃O₄	-	1.49×10^-2[29]	-
Co₃O₄-SrCO₃	-	6.33×10^-2[29]	-

Fig. 2 Highest occupied molecular orbital (HOMO) (or valence-band) and lowest unoccupied molecular orbital (LUMO) (or conduction-band) energy levels relative to the vacuum of representative inorganic hole transport materials (HOMO and LUMO of Spiro-OMeTAD for comparison)[18]

Fig. 3 Physical morphology, synthesis process and related properties of nickel-based oxide materials (a) Comparison of conductivity mapping results for NiO (left) and Li0.05Mg0.15Ni0.8O (right) films[21]; (b) J-V curve of NiOx-based PSCs with molecular doping of F6TCNNQ[34]; (c) Synthetic process of the SRE NiOx (top), Ni species changed with different synthetic processes (bottom-left) and spectrum changes in Ni species caused by SRE (bottom-right), and (d) champion J-V curves of PSCs[35]; (e) Schematic diagram of synthesis process and (f) high-resolution transmission electron microscopy (TEM) image of NiCo2O4 nanocrystals, as well as (g) J-V curves of the champion PSCs[37]. Colorful figures are available on website

Fig. 4 Morphology and related properties of copper-based oxide materials (a) Cross-sectional SEM image and (b) stability performance of the device with different HTL (Spiro-OMeTAD and Cu2O)[26]; (c) Preparation technology, device structure, energy level diagram and (d) J-V curves of Cu2O and CuO films[40]; (e) TEM image of CuGaO2 nanocrystals and (f) stability of the device[45]; (g) J-V curves, structure diagram (PC61BM: [6,6]-phenyl-C61-butyric acid methyl ester) and (h) stability of device based on mp-CuGaO2[39]; (i) Schematic diagram of nanocrystalline structure and (j) stability of devices based on CuCrO2[46]; (k) TEM image of CuScO2 nanocrystals and (l) J-V curves of PSCs[28]. Colorful figures are available on website

Fig. 5 Physical morphology and related properties of other oxides and non-oxides (a) High-resolution TEM image of Co3O4 and (b) J-V curves of PSCs[47]; (c) Time-resolved photoluminescence (TRPL) spectra and (d) J-V curves of PSCs based on Co3O4-SrCO3[50]; (e) PL absorption spectra and (f) J-V curve of PSCs based on CuSCN HTL[16]; (g) Diagram of device structure, (h) J-V curves and (i) light stability of capped PSCs (under constant illumination and different temperature) based on CuSCN HTL and 2D Cs2PbI2Cl2 capping layers[55]

Fig. 6 Effect of element doping on device performance (a) J-V curves and (b) PL spectra of PSCs based on Cu:NiOx HTL[23]; (c) J-V curves of PSCs and (d) electrical conductivity of Cs:NiOx film[27]; (e) SEM image of In doped CuCrO2 film and (f) J-V curves of PSCs[57]; (g) Mott-Schottky curves and (h) J-V curves of PSCs based on the Zn doped CuGaO2[25]

Fig. 7 Effect of additive engineering on device performance (a) SEM images of NiO film with different ammonium stabilizers and different concentrations and (b) J-V curves of PSCs[30]; (c) Schematic structure, (d) J-V curves and (e) I-t curves of PSCs based on NiO film with boric acid[59]; (f) J-V curves, (g) long-term stability and (h) maximum power output stability of PSCs based on ionic liquid-assisted synthesis of NiO NPs[60]; BCP: Bathocuproin; VMPP: Output voltage at maximum power. Colorful figures are available on website

Fig. 8 Effect of interface engineering on device performance (a) J-V curves of devices based on surface modification with different concentrations of CsBr, and stability of PSCs[63]; (b) J-V curves and (c) MPP stability of PSCs based on GUAI surface modification at different concentrations (in molar) with inset showing environmental stability[64]; (d) High-resolution TEM images of Au@NiOx NPs, (e) corresponding structure diagram and (f) J-V curves of PSCs[65]; (g) MPP stability of devices with TMSBr surface modification[66]; CsBr-2.5: 2.5 mg/mL CsBr; RS: reverse scan; FS: forward scan; T80: the time maintaining 80% initial PCE. Colorful figures are available on website

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