The energetic driving force required to drive charge separation across donor/acceptor heterojunctions is a key consideration for organic optoelectronic devices. Herein we report a series of transient absorption and photocurrent experiments as a function of excitation wavelength and temperature for two low-band-gap polymer/fullerene blends to study the mechanism of charge separation at the donor...

The structure and the electronic properties of single-walled zigzag BN and B3C2N3 nanotubes (n, 0; n=4–10) were investigated using first-principles calculations based on a density functional theory. A plane–wave basis set with periodic boundary conditions in conjunction with Vanderbilt ultrasoft pseudo-potential was employed. The energy gap of ZB3C<su...

Further improvement of the power conversion efficiencies of conventional perovskite ferroelectric oxides has been strongly impeded by their wide band gaps. Here, we use several band gap engineering strategies to design low band gap ferroelectric materials from first principles. We show that polarization rotation is useful for reducing the band gaps of strongly distorted perovskites. A variety o...

Materials and structures that strongly discriminate electromagnetic radiation based on one, or more of its properties (e.g. polarization, frequency) play an enabling role for a wide range of physical phenomena. For example, polarizers can selectively transmit light based on its polarization [1] over a wide range of frequencies; photonic crystals [2] (PhCs) can reflect light of certain frequenci...

Boron arsenide, the typically-ignored member of the III–V arsenide series BAs–AlAs–GaAs– InAs is found to resemble silicon electronically: its Γ conduction band minimum is p-like (Γ15), not s-like (Γ1c), it has an X1c-like indirect band gap, and its bond charge is distributed almost equally on the two atoms in the unit cell, exhibiting nearly perfect covalency. The reasons for these are tracked...

The analogy between electromagnetic wave propagation in multidimensionally periodic structures and electronwave propagation in real crystals has proven to be a fruitful one. Initial efforts were motivated by the prospect of a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden irrespective of the propagation direction in sp...

The structure and the electronic properties of single-walled zigzag BN and B3C2N3 nanotubes (n, 0; n=4–10) were investigated using first-principles calculations based on a density functional theory. A plane–wave basis set with periodic boundary conditions in conjunction with Vanderbilt ultrasoft pseudo-potential was employed. The energy gap of ZB3C<su...

Despite the many advantages (e.g., suitable band gap, exceptional optical absorptivity, earth abundance) of pyrite as a photovoltaic material, its low open-circuit voltage (OCV) has remained the biggest challenge preventing its use in practical devices. Two of the most widely accepted reasons for the cause of the low OCV are (i) Fermi level pinning due to intrinsic surface states that appear as...

In this paper, we have studied the strain, band-edge, and energy levels of cubic InGaAs quantum dots (QDs) surrounded by GaAs. It is shown that overall strain value is larger in InGaAs-GaAs interfaces, as well as in smaller QDs. Also, it is proved that conduction and valence band-edges and electron-hole levels are size dependent; larger QD sizes appeared to result in the lower recombination...