Rigorous wave-optical treatment of photon recycling in thermodynamics of photovoltaics: Perovskite thin-film solar cells

Abstract

The establishment of a rigorous theory on thermodynamics of light management in photovoltaics that accommodates various loss mechanisms as well as wave-optical effects in the absorption and reemission of light is at stake in this contribution. To this end, we propose a theoretical framework to calculate the open-circuit voltage enhancement resulting from photon recycling (∆V PR oc ) with rigorous wave-optical treatment. It can be applied to both planar thin-film and nanostructured single-junction solar cells. We derive an explicit expression for ∆V PR oc , which reveals its dependence on internal quantum luminescence efficiency, parasitic reabsorption, and on photon escape probabilities of reemmited photons. While the internal quantum luminescence efficiency is an intrinsic material property, both latter quantities can be determined rigorously for an arbitrary solar cell architecture by three-dimensional electrodynamic dipole emission calculations. We demonstrate the strengths and validity of our framework by determining the impact of photon recycling on the Voc of a conventional planar organo-metal halide perovskite thin-film solar cell and compare it to established reference cases with perfect antireflection and Lambertian light scattering. Our calculations reveal ∆V PR oc values of up to 80 mV for the considered device stack in the absence of angular restriction and up to 240 mV when the escape cone above the cell is restricted to θout = 2.5 • around the cell normal. These improvements impose severe constraints on the parasitic absorption as a parasitic reabsorption probability of only 2% reduces the ∆V PR oc to 100 mV for the same angular restriction. Our work here can be used to provide design guidelines.

The Dominant Energy Transport Pathway in Halide Perovskites: Photon Recycling or Carrier Diffusion?

“…[61,62] The internal QY is expected to approach unity. [30] As demonstrated by Abebe et al, [20] when η IN is higher than 0.3, efficient photon recycling is expected, even adequately enhancing the open-circuit voltage. α 0 and d 0 are average absorption coefficient and absorber thickness, respectively.…”

“…[20,64] Moreover, one of the most important factors proposed for the high efficiency of perovskite solar cells is their long carrier diffusion length. When emission is reabsorbed in the interior, carriers are regenerated, resulting in a redistribution of carriers locally.…”

“…[20] Whereas, high diffusion coefficients may reduce V OC in the presence of nonradiative surface recombination. For solar cells, carrier diffusion and photon recycling imply different impacts on open-circuit voltage.…”

“…[18,19] Photon recycling refers to the regeneration of an excitation via the self-reabsorption of emission from recombining photogenerated charge pairs. [18][19][20][21] As demonstrated previously, photon recycling will boost an additional open-cir-) according to, [20] ln 1 1where k is the Boltzmann constant, q is the elementary charge of an electron, T C is the cell temperature, η IN is the internal quantum efficiency, and p r is the probability of photon recycling. [18][19][20][21] As demonstrated previously, photon recycling will boost an additional open-cir-…”

“…[14][15][16][17] Regarding the solar cells, the diffusion of photogenerated carriers and photon recycling are the two possible energy transport pathways that could affect the internal carrier dynamics and device performances. [18][19][20][21] Both processes may cause a similar influence in the external emission wavelength. Whereas, their influences on carrier lifetime, external photoluminescence (PL) quantum yield (QY), as well as opencircuit voltage (V OC ) and efficiency of the solar cells are different.…”