Methodology for vetting heavily doped semiconductors for intermediate band photovoltaics: A case study in sulfur-hyperdoped silicon

Abstract

We present a methodology for estimating the efficiency potential for candidate impurity-band photovoltaic materials from empirical measurements. This methodology employs both Fourier transform infrared spectroscopy and low-temperature photoconductivity to calculate a "performance figure of merit" and to determine both the position and bandwidth of the impurity band. We evaluate a candidate impurity-band material, silicon hyperdoped with sulfur; we find that the figure of merit is more than one order of magnitude too low for photovoltaic devices that exceed the thermodynamic efficiency limit for single band gap materials. V C 2013 AIP Publishing LLC. [http://dx

Picosecond carrier recombination dynamics in chalcogen-hyperdoped silicon

“…For the sample with S concentration at 1.2 Â 10 20 cm À3 , the figure of merit from our result is consistent with previous reports. 16 Our data show that at N above the IMT, the sample has the lowest figure of merit (0.04). On the other hand, the highest figure of merit is just below 0.5 in a lower dose sample with S concentration at 1.4 Â 10 19 cm…”

“…13 Microwave photoconductivity decay and low-temperature photoconductivity measurements on carrier dynamics in this material lack the time-resolution required to measure the lifetime directly. [14][15][16] Similar to microwaves, THz radiation is long-wavelength electromagnetic radiation and is sensitive to free charge carriers. Moreover, subpicosecond-duration THz pulses can be straightforwardly generated, enabling direct mapping of the carrier recombination dynamics on picosecond time scales.…”

“…17 To fabricate S-and Se-hyperdoped Si samples, we use ion-implantation followed by nanosecond pulsed-laser melting and rapid resolidification, a well-established method for fabricating high quality single crystalline samples with N above the equilibrium solid-solubility limit. 18 Variation in N is achieved by varying the implantation dose ranging from 1 Â 10 14 to 1 Â 10 16 ions/cm 2 . The Si wafers used are 800-lm thick, double-side polished and p-type (boron doped with resistivity of 10-30 X Á cm).…”

Application of Ion Implantation for Intermediate Energy Levels Formation in the Silicon-Based Structures Dedicated for Photovoltaic Purposes

“…As it was assumed, occurrence of this new band could allow the photons of energy lower than E g to be absorbed, generating additional photocurrent and consequently, increasing the PV cells efficiency. The possibility of IB formation was confirmed experimentally for different impurities such as titanium [12], sulphur [13], selenium and tellurium [14]. Moreover, this may be be possible for other elements such as chalcogens or transition metals.…”

“…In this context, it is reasonable to investigate if it is possible to induce a shift in the value of E g using appropriately configured ion implantation and whether such operation will influence the performance of PV cells. Since the ion implantation and post-implantation treatment are the processes that require predetermining of a number of correlated variables, the aspect of consideration was a matter of many experimental and theoretical studies [11][12][13][14][15].…”