Band offset at the heterojunction interfaces of CdS/ZnSnP2, ZnS/ZnSnP2, and In2S3/ZnSnP2

Nakatsuka, Shigeru; Nosé, Yukihiko; Shirai, Yoshihito

doi:10.1063/1.4950882

Cited by 13 publications

(7 citation statements)

References 32 publications

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“…Hence, the large series resistance comes from resistances at the interfaces of CdS/ZnSnP 2 and/or ZnSnP 2 /Mo, and the further investigation is necessary to clarify the effect of interfaces. On the other hand, the small value of the open‐circuit voltage, V OC , 0.172 V, might be attributed to the large conduction band offset (CBO) between CdS and ZnSnP 2 , −1.2 eV , which makes a cliff at their interface and limits the value of V OC . In the viewpoint of the conduction band offset, it was suggested that ZnS and In 2 S 3 were suitable materials as a buffer layer.…”

Section: Resultsmentioning

confidence: 99%

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Nakatsuka

Yuzawa

Chantana

et al. 2016

Phys. Status Solidi A

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We report on current density–voltage (J–V) characteristics of solar cells using bulk crystals of ZnSnP2 obtained by solution growth, where Sn was used as a solvent. The minority carrier lifetimes of fast and slow components in bulk crystals of ZnSnP2 were 0.442 and 37.8 ns, respectively, which were obtained by analysis using double exponential function in time‐resolved photoluminescence (TRPL) under the excitation power of 5.05 mW with the beam area of 0.5 mm2. The lifetime is close to that of CIGS, which is as high as to achieve the conversion efficiency of over 16%. TRPL also revealed that the recombination at the surface was dominant since the intensity of fast component was much larger than that of slow component. The well‐known structure Al/Al‐doped ZnO/ZnO/CdS/ZnSnP2/Mo was adopted for solar cells. The short‐circuit current density and the open‐circuit voltage are 1.99 mA cm−2 and 0.172 V, respectively. The wavelength at the absorption edge in external quantum efficiency is consistent with the bandgap of ZnSnP2. However, the conversion efficiency is 0.087%. The J–V curve suggests that the reduction of series resistance is required because it is higher than the value expected from the resistivity of bulk ZnSnP2. The improvement of conduction band offset is also necessary considering from our previous works.

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Section: Resultsmentioning

confidence: 99%

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Nakatsuka

Yuzawa

Chantana

et al. 2016

Phys. Status Solidi A

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“…For Pb-PSCs, the CBO at the ETL/perovskite layer interface is close to zero when TiO 2 or fullerenes are used to form the ETL. However, Sn-based perovskite materials have been reported to have lower electron affinities than Pb-based perovskite materials. , Therefore, the CBO at the ETL/perovskite layer interface is high when these common ETL materials are used. − The energy band offset at the heterojunction interface generally affects the V OC in solar cells such as Cu(In,Ga)Se 2 (CIGS) and Cu 2 ZnSnS 4 (CZTS) solar cells. − Minemoto et al investigated the relationship between the V OC and the CBO at the ETL/perovskite layer interface theoretically for a p-i-n heterojunction device composed of Sn–Ge mixed perovskites and showed that the CBO had a strong influence on the V OC . However, their work did not compare Sn-PSCs and Pb-PSCs and it thus remains unclear why the Sn-PSCs have a comparatively large V OC loss.…”

Section: Introductionmentioning

confidence: 99%

Improving the Open-Circuit Voltage of Sn-Based Perovskite Solar Cells by Band Alignment at the Electron Transport Layer/Perovskite Layer Interface

Yokoyama

Miyamoto

et al. 2020

ACS Appl. Mater. Interfaces

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Organic−inorganic lead halide perovskites are promising materials for realization of low-cost and high-efficiency solar cells. Because of the toxicity of lead, Sn-based perovskite materials have been developed as alternatives to enable fabrication of Pb-free perovskite solar cells. However, the solar cell performance of Sn-based perovskite solar cells (Sn-PSCs) remains poor because of their large open-circuit voltage (V OC ) loss. Sn-based perovskite materials have lower electron affinities than Pb-based perovskite materials, which result in larger conduction band offset (CBO) values at the interface between the Snbased perovskite and a conventional electron transport layer (ETL) material such as TiO 2 . Herein, the relationship between the V OC and the CBO in these devices was studied to improve the solar cell performances of Sn-PSCs. It was found that the band offset at the ETL/ perovskite layer interface affects the V OC of the Sn-PSCs significantly but does not affect that of the Pb-PSCs because the Sn-based perovskite material is a p-type semiconductor, unlike the Pb-based perovskite. It was also found that Nb 2 O 5 has the CBO that is closest to zero for Sn-based perovskite materials, and the V OC values of Sn-PSCs that use Nb 2 O 5 as their ETL are higher than those of Sn-PSCs using TiO 2 or SnO 2 ETLs. This study indicates that control of the energy alignment at the ETL/perovskite layer interface is an important factor in improving the V OC values of Sn-PSCs.

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“…In this device, the value of V OC was significantly low considering the bandgap of ZnSnP 2 . XPS measurements revealed that CdS/ZnSnP 2 showed a large conduction band offset, ΔE C = −1.2 eV, 24 which suggested that band alignment was necessary to achieve a high conversion efficiency.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of CdSnP₂ Thin Films by Phosphidation for Photovoltaic Application

Nakatsuka

Inoue

Nosé

2018

ACS Appl. Energy Mater.

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We report on the fabrication of CdSnP2 thin films for photovoltaic application. The phosphidation method, where co-sputtered Cd-Sn precursor thin film reacts with phosphorus gas, was utilized for the preparation of CdSnP2 thin films. In order to establish the fabrication process, the temperature dependence on product phases was investigated and CdSnP2 thin films were obtained by the phosphidation at 350 C for 30 min under the phosphorus vapor pressure of 10 −2 atm. CdSnP2 thin films showed a n-type conduction.The resistivity, the carrier concentration and the mobility were evaluated to be 3.5−3.7×10 2 Ω cm, 1−3×10 15 cm −3 and 4.7−17 cm 2 V −1 s −1 , respectively. CdSnP2 thin films with relatively flat and smooth surface were obtained, although it was reported that ZnSnP2 with the same crystal structure grew as the protrusion shape by the VLS growth mode. In order to investigate these difference in growth mechanism between CdSnP2 and ZnSnP2, the reaction process in Cd-Sn-P system was investigated and discussed based on the chemical potential diagrams. As the result, it was understood that Cd, Sn and P4 directly reacted to form CdSnP2, while ZnSnP2 was formed via the reaction among Zn3P2, Sn and P4 after Zn reacts with P4 to produce Zn3P2. Therefore, it is speculated that simple reaction route results in the high growth speed and smooth flat morphology was obtained in the fabrication of CdSnP2 thin films..

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Band offset at the heterojunction interfaces of CdS/ZnSnP2, ZnS/ZnSnP2, and In2S3/ZnSnP2

Abstract: Band gap of sphalerite and chalcopyrite phases of epitaxial

Cited by 13 publications

References 32 publications

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Improving the Open-Circuit Voltage of Sn-Based Perovskite Solar Cells by Band Alignment at the Electron Transport Layer/Perovskite Layer Interface

Fabrication of CdSnP₂ Thin Films by Phosphidation for Photovoltaic Application

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Band offset at the heterojunction interfaces of CdS/ZnSnP2, ZnS/ZnSnP2, and In2S3/ZnSnP2

Abstract: Band gap of sphalerite and chalcopyrite phases of epitaxial

Cited by 13 publications

References 32 publications

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP2

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP2

Improving the Open-Circuit Voltage of Sn-Based Perovskite Solar Cells by Band Alignment at the Electron Transport Layer/Perovskite Layer Interface

Fabrication of CdSnP2 Thin Films by Phosphidation for Photovoltaic Application

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Product

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Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Solar cells using bulk crystals of rare metal-free compound semiconductor ZnSnP₂

Fabrication of CdSnP₂ Thin Films by Phosphidation for Photovoltaic Application