研究目的
Investigating the enhancement of colloidal quantum dot tandem solar cell performance by graded band alignment.
研究成果
A graded band alignment has been applied to the rear cell leading to a PCE of 6.8% for the tandem cell by enhancing carrier transport. The interlayer applied in this research has effectively connected the front and rear cells as demonstrated by the matched current. This simple and effective recombination layer and the graded band alignment strategy can both be used widely in other tandem cell scenarios.
研究不足
The relatively small diffusion length in colloidal quantum dot solar cells limits the quantum dot absorbing layer thickness and hence the power conversion efficiency. The experimental current densities are lower than the simulated theoretical maximum values due to reflection loss caused by the measurement method and recombination loss.
1：Experimental Design and Method Selection:
Optical modelling was used to establish the appropriate absorbing layers’ thicknesses to achieve current matching of front and rear cells. The modelled cell structure consists of layers of ITO glass / ZnO-NP(120 nm) / Front cell absorbing layer(Eg=
2：44 eV, thickness is a variable.) / Au(2 nm) / ZnO-NP(80 nm) / Rear cell absorbing layer (Eg=22 eV, Thickness is a variable) / Au. Sample Selection and Data Sources:
The optical parameters, n and k, of the PbS QD layers with different bandgaps were calculated by fitting spectroscopic ellipsometry data using WVase software.
3：List of Experimental Equipment and Materials:
PVlighthouse SunsolveT M modules with modifications, spectroscopic ellipsometry data, ZnO nanoparticles, PbS quantum dots.
4：Experimental Procedures and Operational Workflow:
The thicknesses of the front and rear cell absorbing layers are varied while other functional layers’ thicknesses are taken to be fixed.
5：Data Analysis Methods:
The approach for analyzing experimental data included statistical techniques and software tools utilized for optical modelling.
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