International audienceThe quest of higher conversion efficiencies of solar cells has led to the improvement of material properties and the design of new structures for a better use of the solar spectrum. One of the most promising thin-film silicon solar cell concepts is “Micromorph” tandem solar cells consisting of a microcrystalline silicon bottom subcell and an amorphous silicon top subcell. In this paper, a micromorph tandem solar cell (a-Si:H/µc-Si:H) with an intermediate microcrystalline tunnel recombination junction (TRJ) has been designed and analyzed by simulations using AMPS-1D (Analysis of Microelectronic and Photonic Structures) device simulator. A higher efficiency for the micromorph tandem has been achieved by optimizing each subcell and the TRJ. The open-circuit voltage VOC is improved and it is nearly the sum of the VOCs of the two corresponding subcells. However, the fill factor FF and short-circuit current JSC are lower in comparison to the single amorphous solar cells. The spectral response behavior of the micromorph tandem has shown better utilization of solar spectrum. © 2016 Taylor & Francis Group, LLC

Recently polycrystalline silicon (pc-Si) thin film transistors (TFT’s) have emerged as the devices of choice for many applications. The TFTs made of a thin un-doped polycrystalline silicon film deposited on a glass substrate by the Low Pressure Chemical Vapor Deposition technique LPCVD have limits in the technological process to the temperature < 600°C. The benefit of pc-Si is to make devices with large grain size. Unfortunately, according to the conditions during deposition, the pc-Si layers can consist of a random superposition of grains of different sizes, where grains boundaries parallels and perpendiculars appear. In this paper, the transfer characteristics IDS-VGS are simulated by solving a set of two-dimensional (2D) drift-diffusion equations together with the usual density of states (DOS: exponential band tails and Gaussian distribution of dangling bonds) localized at the grains boundaries. The impact of thickness of the active layer on the distribution of the electrostatic potential and the effect of density of intergranular traps states on the TFT’s transfer characteristics IDS-VGS have been also investigated.

Recently polycrystalline silicon (pc-Si) thin film transistors (TFT's) have emerged as the devices of choice for many applications. The TFT's made of a thin un-doped polycrystalline silicon film deposited on a glass substrate by the Low Pressure Chemical Vapor Deposition technique LPCVD have limits in the technological process to the temperature < 600°C. The benefit of pc-Si is to make devices with large grain size. Unfortunately, according to the conditions during deposition, the pc-Si layers can consist of a random superposition of grains of different sizes, where grains boundaries parallels and perpendiculars appear. In this paper, the transfer characteristics I DS -V GS are simulated by solving a set of two-dimensional (2D) drift-diffusion equations together with the usual density of states (DOS: exponential band tails and Gaussian distribution of dangling bonds) localized at the grains boundaries. The impact of thickness of the active layer on the distribution of the electrostatic potential, the effect of density of intergranular traps states and grain size on the TFT's transfer characteristics I DS -V GS have been also investigated.