1. 2 New Materials and Concepts for Cells and Modules
Summary / Abstract:
In the rapidly evolving field of multijunction solar cells, the increasing advantages and market breakthroughs in silicon have led to intense research in silicon based tandems. A parallel axis of intensive research is the breakthrough perovskite materials family for the high bandgap junction. In this context, three terminal devices are receiving increasing attention [1,2,3] given benefits they present over the traditional two and four terminal approaches. This paper reports recent progress on a new three terminal device design, the selective band offset barrier tandem solar cell , in the context of a European project introduced at the recent 36th EUPVSEC . The function of the selective barrier between top and bottom cells is to allow one type of photogenerated carrier to pass, whilst inhibiting thermalisation of majority carriers from the top (perovskite) cell in the bottom (silicon interdigitated back contact) cell. The results reported cover theoretical and experimental progress. First we present a study of two, three, and four terminal designs. This provides context to the presented advantages of the proposed novel selective band offset interdigitated back contact design. The second axis of research is the identification of a range of candidate materials. This relies both on existing databases of materials properties and on a significant element of ab-initio materials properties modelling which includes optical properties and interface properties in particular, and electronic tansport properties where possible. Theoretical studies of device performance are presented exploiting these materials parameters via a two dimensional numerical device model, including all important interface property modelling, yielding a multiscale modelling approach, from atomic to device scales. This theoretical context introduces the experimental results obtained in the first year of the project. This consists of successful integration of the selective band offset barrier on a suitably modified IBC structure using prototype materials previously reported. This paper thereby presents detailed analysis of the three terminal selective band offset barrier tandem solar cell, with experimental results on this novel high efficiency structure.