A Microscopic Perspective on Photovoltaic Reciprocity in Ultrathin Solar Cells

Abstract

The photovoltaic reciprocity theory relates the electroluminescence spectrum of a solar cell under applied bias to the external photovoltaic quantum efficiency of the device as measured at short circuit conditions. Its derivation is based on detailed balance relations between local absorption and emission rates in optically isotropic media with non-degenerate quasi-equilibrium carrier distributions. In many cases, the dependence of density and spatial variation of electronic and optical device states on the point of operation is modest and the reciprocity relation holds. In nanostructure-based photovoltaic devices exploiting confined modes, however, the underlying assumptions are no longer justifiable. In the case of ultrathin absorber solar cells, the modification of the electronic structure with applied bias is significant due to the large variation of the built-in field. Straightforward use of the external quantum efficiency as measured at short circuit conditions in the photovoltaic reciprocity theory thus fails to reproduce the electroluminescence spectrum at large forward bias voltage. This failure is demonstrated here by numerical simulation of both spectral quantities at normal incidence and emission for an ultrathin GaAs p-i-n solar cell using an advanced quantum kinetic formalism based on non-equilibrium Green's functions of coupled photons and charge carriers. While coinciding with the semiclassical relations under the conditions of their validity, the theory provides a consistent microscopic relationship between absorption, emission and charge carrier transport in photovoltaic devices at arbitrary operating conditions and for any shape of optical and electronic density of states.

5 pages, 4 figures, all figures replaced, minor changes and additions to the text

References in corpus (5)

• Theory and simulation of quantum photovoltaic devices based on the non-equilibrium Green's function formalism
• Simulation of nanostructure-based and ultra-thin film solar cell devices beyond the classical picture
• Simulation of Ultra-thin Solar Cells Beyond the Limits of the Semi-classical Bulk Picture
• Efficiency of thin film photocells
• Impact of built-in fields and contact configuration on the characteristics of ultra-thin GaAs solar cells

Cited by in corpus (7)

• Rigorous Treatment of Photon Recycling in Thermodynamics of Photovoltaics: The Case of Perovskite Thin-Film Solar Cells
• Generalized Reciprocity Relations in Solar Cells with Voltage-Dependent Carrier Collection: Application to p-i-n Junction Devices
• Shockley-Queisser Model: Analytical Solution, Thermodynamics, and Kinetics
• Nonequilibrium theory of the conversion-efficiency limit of solar cells including thermalization and extraction of carriers
• Quantum-kinetic perspective on photovoltaic device operation in nanostructure-based solar cells
• Optoelectronic Reciprocity in Hot Carrier Solar Cells with Ideal Energy Selective Contacts
• Impact of electron-phonon scattering on optical properties of CH${}_3$NH${}_3$PbI${}_3$ hybrid perovskite material