Band alignment and carrier recombination roles on the open circuit voltage of ETL‐passivated perovskite photovoltaics

Nanocrystal solar cells (NCs) allow for large scale solution processing under ambient conditions, permitting a promising approach for low-cost photovoltaic products. Although an up to 10% power conversion efficiency (PCE) has been realized with the development of device fabrication technologies, the open circuit voltage (Voc) of CdTe NC solar cells has stagnated below 0.7 V, which is significantly lower than most CdTe thin film solar cells fabricated by vacuum technology (around 0.8 V~0.9 V). To further improve the NC solar cells’ performance, an enhancement in the Voc towards 0.8–1.0 V is urgently required. Given the unique processing technologies and physical properties in CdTe NC, the design of an optimized band alignment and improved junction quality are important issues to obtain efficient solar cells coupled with high Voc. In this work, an efficient method was developed to improve the performance and Voc of solution-processed CdTe nanocrystal/TiO2 hetero-junction solar cells. A thin layer of solution-processed CdS NC film (~5 nm) as introduced into CdTe NC/TiO2 to construct hetero-junction solar cells with an optimized band alignment and p-n junction quality, which resulted in a low dark current density and reduced carrier recombination. As a result, devices with improved performance (5.16% compared to 2.63% for the control device) and a Voc as high as 0.83 V were obtained; this Voc value is a record for a solution-processed CdTe NC solar cell.

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Efficiency Improvement in Co-sensitized DSSCs Through a Cascade Band Alignment of N-719 and Rose Bengal Dyes on Nanostructured ZnO Photoanodes

MRS Advances ◽

10.1557/adv.2017.111 ◽

2017 ◽

Vol 2 (14) ◽

pp. 767-775

Author(s):

M.A. Borysiewicz ◽

S. Chusnutdinow ◽

M. Wzorek ◽

T. Wojciechowski

Keyword(s):

Rose Bengal ◽

Open Circuit Voltage ◽

Electrochemical Impedance ◽

Short Circuit ◽

Short Circuit Current ◽

Open Circuit ◽

Band Alignment ◽

Electron Hole ◽

Cell Efficiency ◽

Hole Recombination

ABSTRACTWe show that by subsequent sensitization of nanostructured ZnO photoanodes with N-719 and Rose Bengal dyes an improvement or worsening of the cell efficiency may be obtained, relating to photoanodes sensitized with N-719 dye only (JSC = 2.97 mA/cm2, VOC = 0.68 V, η = 0.99%) depending on the order in which the dyes are applied. We observe that for the case when the N-719 dye is followed by Rose Bengal an increase in efficiency, short circuit current and open circuit voltage is observed (JSC = 3.95 mA/cm2, VOC = 0.71 V, η = 1.26%), which we relate to the cascade band alignment of the ZnO and the dyes. In the case when Rose Bengal is first on ZnO followed by N-719, a lowering of all parameters is observed (JSC = 2.86 mA/cm2, VOC = 0.64 V, η = 0.94%) due to the trap band alignment. Electrochemical impedance spectroscopy measurements and modelling confirmed this theory showing longer electron lifetimes in the photoanode for the cascade band alignment, enhancing electron-hole separation, than for the trap alignment, facilitating electron-hole recombination.

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Carbon-Quantum-Dot-Hybridized NiOx Hole-Transport Layer Enables Efficient and Stable Planar p-i-n Perovskite Solar Cells with High Open-Circuit Voltage

Journal of Materials Chemistry C ◽

10.1039/d1tc02595c ◽

2021 ◽

Author(s):

Xuefeng Xia ◽

Dan Zhang ◽

Xiaofeng Wang ◽

Zonghu Xiao ◽

Fan Li

Keyword(s):

Solar Cell ◽

Open Circuit Voltage ◽

Perovskite Solar Cells ◽

Perovskite Solar Cell ◽

Open Circuit ◽

Hole Transport ◽

Band Alignment ◽

Transport Layer ◽

Hole Transport Layer ◽

Carbon Quantum Dot

In recent years, the nickel oxide (NiOx)-based planar p-i-n perovskite solar cell (PSC) has progressed rapidly. Nevertheless, poor electrical properties of NiOx, unoptimized band alignment between NiOx and perovskites, as...

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