Intermediate band solar cells: Recent progress and future directions

Abstract

Extensive literature and publications on intermediate band solar cells (IBSCs) are reviewed. A detailed discussion is given on the thermodynamics of solar energy conversion in IBSCs, the device physics, and the carrier dynamics processes with a particular emphasis on the two-step inter-subband absorption/recombination processes that are of paramount importance in a successful implementation high-efficiency IBSC. The experimental solar cell performance is further discussed, which has been recently demonstrated by using highly mismatched alloys and high-density quantum dot arrays and superlattice. IBSCs having widely different structures, materials, and spectral responses are also covered, as is the optimization of device parameters to achieve maximum performance.

Nonlinear optical response and structural properties of MBE-grown Fe:ZnS films

“…Z-scan measurements [29-31] were performed using 11 ns laser pulses at 532 nm with a 10Hz repetition rate to determine separately the nonlinear refraction and the nonlinear absorption of the samples, related to the real and imaginary parts of the third order nonlinear susceptibilities, respectively (Re χ (3) , Im χ (3) ). At this wavelength, the linear absorption due to imperfections is approximately a factor of two higher than at the wavelength used for OKE studies.…”

“…Transition metal substitution in II-VI semiconductors has been a rich area of study for over 50 years [1] but new applications, including dilute magnetic semiconducting devices [2], intermediate band solar cells [3], and mid-infrared lasers [4,5] are driving further development of these materials. In particular, both ZnS and ZnSe have suitable properties as hosts for passive Qswitch and gain species in the mid-infrared region.…”

Band-edge modification and mid-infrared absorption of co-deposited Fe_xZn_1-xS thin films

“…The location of the Fermi level, within the Fe intragap states for the doped material, suggests this as a candidate for demonstration of the intermediate band solar cell concept [29].…”

Guided-Mode Resonance Gratings for Intermediate Band Quantum Dot Solar Cells

“…Quantum dots (QDs) are well suited as an IB material as they form three-dimensional potential wells that provide bound states fully isolated from the continuum bands owing to their zero-dimensional density of states [2]. Strong interband and intraband optical absorption is needed [1] to make QD solar cells operate in the IB regime and reach high efficiency, but from the practical standpoint the QD material effective absorption is limited by the relatively low QD density and low number of QD layers that can be used in the solar cell without compromising the crystal quality. Taking advantage of a thin-film configuration, novel photon management techniques applied to QD solar cells may overcome such limitation [3].…”

“…Efficiency enhancement of solar cells through the use of intermediate band (IB) materials exploits the sequential absorption of two sub-bandgap photons to achieve large photocurrent and high voltage at the same time [1,2]. The sequential two-photon absorption requires the introduction in the semiconductor forbidden band gap of an energy level or band which supports strong optical transitions from and to the valence band (VB) and conduction band (CB), respectively, while being electrically isolated from them.…”