Charge photo-carrier transport from silicon nanocrystals embedded in SiO2-based multilayer structures

Abstract

Structural and optoelectronical characterization of Si -SiO 2 / SiO 2 multilayers with applications in all Si tandem solar cells J. Appl. Phys. 107, 064321 (2010) Experimental investigation of photoconductivity in Si-rich silicon oxide (SRSO)/SiO 2 multilayer (ML) structures prepared by magnetron reactive sputtering is reported. Photocurrent (PC) measurements show that the PC threshold increases with decreasing the thickness of SRSO layer. Photo-conduction processes in our samples are shown to be dominated by carrier transport through quantum-confined silicon nanocrystals embedded in the SiO 2 host. In addition, the observed bias-dependence of photocurrent intensity is consistent with a model in which carrier transport occurs by both tunneling and hopping through defect states in the silicon oxide matrix. A photocurrent density J ph of 1-2 mA cm À2 is extracted from our results. Although this photocurrent density along the ML absorber film is relatively low, the results presented in this work are believed to be a valuable contribution toward the implementation of all-Si tandem solar cells. V C 2012 American Institute of Physics. [http://dx

Narrow band photocurrent response from partially phase separated a-SiNx:H thin films

“…Further, the role of Si inclusions in the observed features may be ruled out, as their expected response should come in the red region of the spectrum. 27 To elaborate further, if we consider the band gap of quantum confined Si (from Park et al 28 ), a sharp response is expected in the UV-blue region for a-Si inclusions having narrow size distribution of $1.5 nm. However, the films in the present case are partially phase separated with large variation of the sizes (2 to 10 nm) of the a-Si inclusions.…”

High efficiency Si quantum dot heterojunction solar cells using a single SiOX:B layer

“…However, photoexcited carrier transport and the number of generated Si QDs in this structure is restricted by the adjacent SiO 2 layer, which has a crucial impact on the efficiency of Si QD based photovoltaic cells. [8,13] Recently, we have fabricated Si QD heterojunction solar cells with 14.8% efficiency from a boron-doped single SiO x layer (SiO x :B) [14]. In addition, we have studied the importance of the B doping concentration for effective electronic band engineering of the absorption layer in Si QD heterojunction solar cells [15].…”