LETTER Refractory plasmonics boost the performance of thin-film solar cells Ayman E. Selmy 1 & Moamen Soliman 1 & Nageh K. Allam 1 Received: 25 June 2018 /Accepted: 8 November 2018 # Springer Nature Switzerland AG 2018 Abstract Plasmonic thin-film solar cells have recently gained a great research attention due to the tunability of plasmonic nanoparticles with efficient light trapping characteristics. Although noble metals have shown great optoelectronic properties, they are expen- sive, rare, and unavailable for large-scale production and integration. Herein, the possibility to replace noble metals with transition metal nitrides/oxynitrides as refractory plasmonic materials is presented through finite-difference-time-domain BFTDT^ simulations. Titanium nitride BTiN^ promises mass-production on lower-cost as well as abundance relative to noble metals, along with being complementary metal oxide semiconductor BCMOS^ process compatible. The similar optoelectrical properties between transition metals and noble metals, such as gold or silver, make this replacement possible, and interesting to investigate. The plasmonic effect of TiN across the scattering and absorption cross-section is simulated, and the results are demonstrated and discussed. Afterwards, the I-V characteristics for a 2 μm thin-film solar cell with TiN nanoparticles with different configurations are presented. Then, multiple sizes of multiple nanostructures are analyzed, simulated, and presented, targeting the closest scattering and coupling-to-substrate efficiency to gold nanoparticles, and hence better overall efficiency. Keywords Solar cells . Surface plasmon . Light trapping . Device physics . Silicon 1 Introduction To date, fossil fuel still dominates the current global power generation activity. However, it is not guaranteed for next generations. Alternatively, every hour the sun hits our planet with more energy than all of the global annual energy con- sumed in an entire year [1]. Consequently, there is a growing interest to convert solar light into electricity by means of ro- bust, dependable, low-cost, and efficient devices. In this re- gard, silicon has been the mainstream material for large-scale manufacturing of photovoltaic devices due to its abundance, nontoxicity, chemical stability, CMOS compatibility, and ma- turity of its fabrication techniques. Although silicon is prom- ising for photovoltaic cells, the manufacturing costs are limit- ing its expansion, which can hardly be competitive or attrac- tive versus fossil fuel. Currently, 90% of the solar cell market is based on first-generation photovoltaic cells, with thick- nesses ranging around 200–300 μm[2]. Around 40% of the cost of a solar cell made from crystalline silicon is the cost of the preparation of the silicon wafers. A systematic approach toward cost reduction is via the use of thin silicon absorbers in thin-film fashion or second-generation photovoltaic cells [3, 4]. Thin-film photovoltaics are considered an evolution from the first-generation photovoltaics, targeting reduction of the cost of photovoltaic cells. By 2020, the solar cells power gen- erations will exceed 50 GW. Thus, reducing the production costs by slimming the absorbing layer seems promising [5]. Thin-film silicon solar cells involve Si absorber deposited on a foreign substrate such as glass, ceramics, or metals with a thickness of only a few micrometers. However, the efficiency of thin-film solar cells is still below the maximum theoretical efficiency due to the poor light absorption at longer wave- lengths owing to the indirect bandgap of Si, and the very high surface and bulk recombination rates [6]. Moreover, the use of thin absorbing layers reduces the short-circuit current density due to the decreased electron-hole pair path length in the semiconductor. Additionally, semiconductor surface rough- ness results in increased surface recombination, with semicon- ductors deposited on rough surfaces typically have low mate- rial quality [7]. The discovery of Raman scattering intensifies the interest to explore the optical properties of metal particles [3, 4]. Near- field amplification occurs due to the particle curved surface that exerts an effective restoring force on the driven electrons. * Nageh K. Allam nageh.allam@aucegypt.edu 1 Energy Materials Laboratory, School of Sciences and Engineering, The American University in Cairo, New Cairo 11835, Egypt Emergent Materials https://doi.org/10.1007/s42247-018-0017-x