Single crystal growth and phase stability of photovoltaic grade ZnSiP2 by flux technique
ZnSiP2 is a potential optoelectronic material with possible application in lasers, LED's, photonic integrated circuits, and photovoltaics. The development of ZnSiP2 as a photovoltaic material could address the current technological challenge of implementing a monolithic top cell on silicon for tandem photovoltaics. In this work we present a detailed description of the growth of ZnSiP2 single crystals, which has enabled thorough optoelectronic characterization. A flux growth technique was used, under various conditions, to grow ZnSiP2 single crystals in Zn solution. The results of these growth experiments, along with analysis of previously determined phase diagrams, show that three secondary phases form as a result of the Zn flux growth technique: Zn3P2, Si, and the remaining Zn flux. Potential reasons for the formation of these particular phases are discussed, but their presence is found to be non-detrimental, and they can easily be removed. The resulting single crystals are high purity and enable the characterization of the fundamental optoelectronic properties of ZnSiP2.
Predicting the electron affinity of ZnSiP2 semiconductor from first-principle calculations
Tandem photovoltaic architecture is an effective way to improve photoelectric conversion efficiency because of less thermalization loss. ZnSiP2 has the potential to meet the requirements needed for a top cell in tandem silicon-based solar cells. Electron affinity is an important electrical parameter of semiconductor materials, which has not been reported publicly in the literature on ZnSiP2. In this work, electron affinity of ZnSiP2 is investigated by using Vienna ab initio simulation package (VASP). PBE density functional method and HSE06 hybrid functional method are used to optimize the lattice structure and the band structure, respectively. The results are as follows: the lattice constant of ZnSiP2 is 5.420 Å, and the band gap is 2.048 eV. Based on the above work, the electron affinity of ZnSiP2 (001) crystal plane is calculated at different vacuum layer thicknesses, which is 3.056 eV at 16 Å vacuum layer. This work is helpful to the performance simulation and architectural design of ZnSiP2/Si tandem solar cells.
International actors and trade unions during postsocialism and after: the case of Romania
Purpose 
 
 
 
 
The purpose of this paper is to explain why, in spite having a relatively powerful labour movement at the start of the economic transformation, Romania ended up with a highly deregulated system of industrial relations in the aftermath of the global economic crisis of 2009 and with trade unions which seem incapable to defend their interests. 
 
 
 
 
Design/methodology/approach 
 
 
 
 
The authors trace the changing role that Romanian trade unions had in national policy making and show that the beginning of 2000s represents a critical point for the power loss sustained by organised labour. 
 
 
 
 
Findings 
 
 
 
 
The authors argue that a key element for explaining labour’s decline is the growing pressure exercised by various international organisations for the adoption of deregulatory labour market reforms. While during the 1990s this pressure was circumvented by successive governments which peddled back and forth between union wage pressure and fiscal austerity measures, beginning with 2000s, EU accession conditionalities coupled with IMF and World Bank policy recommendations enabled the international deregulation agenda to be implemented without much opposition. 
 
 
 
 
Originality/value 
 
 
 
 
The paper brings new evidence on the impact of international actors on the Romanian collective bargaining and labour market institutions.