Kesterite Cu 2 ZnSnS 4 (CZTS) thin-film solar cells have drawn worldwide attention because of outstanding performance and earth-abundant constituents. However, problems such as coexistence of complex secondary phases, the band tailing issue, short minority lifetime, bulk defects, and undesirable band alignment at p−n interfaces need to be addressed for further efficiency improvement. In this regard, Cd alloying shows promise for dealing with some of these problems. In this work, a beyond 11% efficient Cd-alloyed CZTS solar cell is achieved, and the effects of Cd-alloying and mechanism underpinning the performance improvement have been investigated. The introduction of Cd can significantly reduce the band tailing issue, which is confirmed by the reduction in the difference between the photoluminescence peak and optical band gap (E g ) as well as decreased Urbach energy. The microstructure, minority lifetime, and electrical properties of CZTS absorber are greatly improved by Cd alloying. Further XPS analyses show that the partial Cd alloying slightly reduces the band gap of CZTS via elevating the valence band maximum of CZTS. This suggests that there are opportunities for further efficiency improvement by engineering the absorber and the associated interface with the buffer.

We propose a hot carrier solar cell based on epitaxial growth of a quantum well superlattice and adjacent contact barriers. The concept fulfills required electronic, optical, and several phononic criteria. The first superlattice miniband determines the absorption threshold. The second miniband with appropriate energy width and position provides energy selectivity in situ; contacts are optimized for carrier selectivity exclusively. Electronic transport properties were investigated including elastic random electron–electron scattering, random layer thickness deviation, and illumination as differential absorption per quantum well using a Monte-Carlo code. Carrier extraction probability and energy selectivity strongly suggest a practical implementation of the proposed concept.

A narrow size distribution of quantum dots (QDs) is needed for their application in photovoltaics but collection of such information is difficult. This paper demonstrates the application of Raman spectroscopy as a characterisation tool to extract the size distribution and crystalline fraction of Si QD samples fabricated through the sputter-anneal method. Measured Raman spectra of Si QD materials are de-convoluted into four components according to their origins and Raman scattering by Si QD cores is

Since their advent around the start of the millennium, hot carrier solar cells came into the focus of a broader research community as one of the so-called third generation photovoltaic concepts. As an exciting research field enthusiastically covered by an increasing number of publications, some aspects of hot carrier solar cell research, namely data interpretation and conclusions with respect to high efficiency devices, appear to show some discrepancies. It therefore appeared timely to provide a detailed review of current hot carrier solar cell research from the fundamentals of non-equilibrium carrier dynamics to complete solar cells to enable advancement with the knowledge of solid state and semiconductor physics being fully taken into account. In our work, we discuss the hot carrier non-equilibrium dynamics right from the process of hot carrier generation, going beyond the standard 1-dimensional approach, hence exploring phononic and other dynamic limits as occurring in real materials. Thermodynamic modelling of hot carrier solar cells in the literature presented conversion efficiencies from 0.04 to 84%. This situation called for an evaluation and a comparison against the Shockley-Queisser efficiency limit. The assessment of characterisation techniques used for dynamic and steady-state detection of hot carrier populations form another part of this review, including to what extent certain data can or should be used in regards to hot carrier solar cells. With this wealth of information, we work through III-V, IV-IV, II-VI, and non-trivial materials which were proposed for hot carrier absorbers in the literature. With the physics and materials considered, we then examine energy-selective contact designs which also have to fulfil the criterion of carrier selectivity. Finally, we look at the whole hot carrier solar cell, departing from the original concept to more feasible designs and qualitatively new approaches.