No abstract

In this paper, we present our route to fabricate Cu2ZnSnSe4 (CZTSe) thin films, which allows to achieve reproducible processing of kesterite absorber, that leads to efficiencies in the range of 10%. The article mainly focuses on the annealing process and demonstrates that controlling of the reactor pressure for selenization can be reliably used to tune the losses of volatile constituents in the absorber, enabling adjustments on the properties of the film and solar cell. The findings reveal a noteworthy resilience to small changes of the process parameters in the vicinity of optimum conditions. Interestingly, a certain pressure range for optimum Zn and Sn composition exists, which results in a broad and stable process window and enables reproducible processing of CZTSe with high power conversion efficiencies. The established process also allows simple upscaling of the device area and results in a power conversion efficiency of ≈ 8% on a large area of 2.85 cm2. The highest efficiencies achieved by our process are around 11% for smaller lab scale devices.

Inorganic semiconductor nanoparticles, such as CdSe quantum dots, are considered to be a promising alternative to fullerene derivates for application as electron acceptors in polymer-based bulk heterojunction solar cells. The main potential advantage is the strong light absorption of CdSe nanoparticles with a spectral bandwidth, which can even be tuned, due to the quantum size effect. However, the impact of the particle size on the performance of polymer/CdSe solar cells has remained largely unexplored so far. Therefore, the influence of particle size in hybrid solar cells using a blend of poly(3-hexylthiophene) (P3HT) and quasi-spherical CdSe nanoparticles on relevant cell parameters and the overall solar cell performance is systematically studied in the present work. As the most important result, an increase of the open-circuit voltage (VOC) can be found for smaller nanoparticles and can be explained by an “effective bandgap” model. In contrast, no significant changes of the short-circuit current density with particle size are observed. Smaller particles were found to yield a lower fill factor, compensating the gain in VOC, so that the power conversion efficiency finally turned out to be independent of the particle size in this study. Spectral differences observed in the respective external quantum efficiency spectra of the solar cells can be attributed to size-dependent changes of the particle absorption. Temperature-dependent measurements of the current-voltage (I-V) characteristics suggest that the transport of photogenerated charge carriers in the bulk heterojunction is limited by localized states, with activation energy beyond thermal energy at room temperature.

No abstract

Molybdenum (Mo) is the most commonly used back-contact material for copper zinc tin selenide (CZTSe)-based thin-film solar cells. The effect of a pure Ar plasma and a mixed Ar–N2 plasma on the back-contact interface of CZTSe solar cells is reported in this study.