Emergence of new materials for exploiting highly efficient carrier multiplication in photovoltaics

Abstract

In conventional solar cell semiconductor materials (predominantly Si) photons with energy higher than the band gap initially generate hot electrons and holes, which subsequently cool down to the band edge by phonon emission. Due to the latter process, the energy of the charge carriers in excess of the band gap is lost as heat and does not contribute to the

Electron Transfer at Quantum Dot–Metal Oxide Interfaces for Solar Energy Conversion

“…One decade ago, an explosion of work around the CM concept was registered together with the emergence of colloidal QDs, with the expectation of observing high MEG yields compared to bulk absorbers. This push in the field was linked to the expectation of slow hot carrier relaxation in QDs (the so-called phonon-bottleneck effect). ,, Over the years, a strong debate followed on whether the phonon bottleneck was indeed operative in QDs − and also on whether quantum confinement promotes higher MEG efficiency in nanocrystals with respect to their bulk crystal counterparts. − Independently of these aspects, as a proof of concept, QD-based solar cells demonstrating unambiguously a gain in photocurrent in the UV part of the solar spectrum induced by MEG were reported. , Several kinetic studies on this topic based on QD–MO systems are highlighted in this Review in section .…”

Exciton-Photon Interactions in Semiconductor Nanocrystals: Radiative Transitions, Non-Radiative Processes and Environment Effects

“…and σ g (ω) is the optical conductivity of graphene. The components ofT (1) have an oscillatory dependence upon the inter-dot distance [228], which arises from the Bessel functions appearing as the result of the angular integration in Equation (23). It means that instead of the usual monotonic b −6 dependence of the FRET rate one may have an oscillatory behaviour, controllable by the gate voltage through the graphene Fermi energy (which determines σ g (ω)).…”

“…Further improvement of the light emission properties of such QDs was achieved by fabrication of core-shell structures, successful for several pairs of II-VI [22] and IV-VI [23] materials, where the shell made of a wider band gap material provides a better protection of the quantized electronic states in the QD core [12]. For ZnSe/ZnS core-shell QDs it was revealed, in particular, that thermodynamical (slow) growth of the ZnS-shell on the colloidal ZnSe-core leads to the quantum yield increase because of decreasing amount of the traps at the core-shell interface [24].…”

“…In the past decade, a growing interest has been paid to the multi-exciton dynamics in nanocrystals because of their high potential for photovoltaic applications. Such processes as carrier multiplication (or multiexciton generation) in nanocrystals, as well as the Auger recombination (which is just a fast reverse process), are widely discussed in the literature [23,[42][43][44] and we will consider these effects below. Special attention is traditionally paid to nanostructured silicon [25,[45][46][47][48] because of its widest use in microelectronics, high purity, natural abundance, low cost, and non-toxicity; we shall also dedicate some space to the exciton-photon interactions and main non-radiative processes mentioned above, in Si NCs and related nanostructures.…”

Exciton-photon interactions in semiconductor nanocrystals: {radiative transitions, non-radiative processes,} and environment effects

“…In the past decade, a growing interest has been paid to the multi-exciton dynamics in nanocrystals because of their high potential for photovoltaic applications. Such processes as carrier multiplication (or multi-exciton generation) in nanocrystals, as well as the Auger recombination (which is just a fast reverse process), are widely discussed in the literature 23,[43][44][45] and we will consider these effects below. Special attention is traditionally paid to nanostructured silicon 25,[46][47][48][49] because of its widest use in microelectronics, high purity, natural abundance, low cost, and non-toxicity; we shall also dedicate some space to the exciton-photon interactions and main non-radiative processes mentioned above, in Si NCs and related nanostructures.…”