Intrinsic, P-doped and B-doped nanocrystalline silicon thin films grown at room temperature on flexible substrates for photovoltaic applications

Abstract

Nanocrystalline silicon (nc-Si) thin films in its intrinsic (i-nc-Si), B-doped (p-nc-Si) and P-doped (n-nc-Si) configurations were developed on the flexible substrates at ambient temperature (∼30 °C), using no additional H2 dilution in planar inductively coupled plasma chemical vapour deposition (ICP-CVD) system. A superior crystallinity (∼81%) with electrical conductivity (σD ∼10-7 S cm−1) was achieved for the intrinsic Si thin film by the virtue of the presence of atomic-H in high density within ICP-CVD, which initiates nucleation even at room temperature on the flexible substrates. Substitution of boron (B) dopants at the crystalline Si lattice maintains a high crystallinity (∼80%) and results significantly high electrical conductivity (6 x10-1 S cm−1) in the p-nc-Si thin film. On the contrary, during the growth of n-nc-Si films, a substantial amount of phosphorous (P) dopants, residing at the interstitial position, results in a moderate crystallinity (∼73%) and relatively lesser conductivity (3 x10-1 S cm−1) than the p-nc-Si films. Finally, in the present work i-nc-Si, p-nc-Si and n-nc-Si thin films all are successfully prepared on the flexible substrates at room temperature, with ample crystallinity, wide optical band gap (∼1.9–1.80 eV) and significant electrical conductivity, which appear suitable for the low-cost fabrication of flexible p-i-n solar cells.