Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling

Abstract

In lead halide perovskite solar cells, there is at least one recycling event of electron–hole pair to photon to electron–hole pair at open circuit under solar illumination. This can lead to a significant reduction in the external photoluminescence yield from the internal yield. Here we show that, for an internal yield of 70%, we measure external yields as low as 15% in planar films, where light out-coupling is inefficient, but observe values as high as 57% in films on textured substrates that enhance out-coupling. We analyse in detail how externally measured rate constants and photoluminescence efficiencies relate to internal recombination processes under photon recycling. For this, we study the photo-excited carrier dynamics and use a rate equation to relate radiative and non-radiative recombination events to measured photoluminescence efficiencies. We conclude that the use of textured active layers has the ability to improve power conversion efficiencies for both LEDs and solar cells.

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

“…[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.…”

“…[18][19][20][21] Both processes may cause a similar influence in the external emission wavelength. [18,19] Photon recycling refers to the regeneration of an excitation via the self-reabsorption of emission from recombining photogenerated charge pairs. [18,19] Photon recycling refers to the regeneration of an excitation via the self-reabsorption of emission from recombining photogenerated charge pairs.…”

Cation-Dependent Light-Induced Halide Demixing in Hybrid Organic–Inorganic Perovskites

“…Hybrid metal halide perovskites have recently garnered intense research interest for solar energy conversion and optoelectronic applications due to their excellent properties, such as defect tolerance 1 , long minority carrier lifetimes 2,3 , and high photoluminescence quantum yields 2,4 . Their general crystal structure is described by ABX 3 , typically comprising a monovalent organic cation A (e.g.…”

“…Since improved stability is achieved without sacrificing electronic properties, these compositions are better candidates for photovoltaic applications, especially as wide bandgap absorbers in tandem cells. , and high photoluminescence quantum yields 2,4 . Their general crystal structure is described by ABX 3 , typically comprising a monovalent organic cation A (e.g.…”

“…We have previously reported similar results for the MAPbhalide perovskites. 26 A rise in PLQY at low excitation densities, as observed by multiple groups for MAPbhalide perovskites, 4,24,26,33 is characteristic of the filling of trap states until radiative recombination dominates. 24 At 1sun, the performance of FACsPbhalides is limited by nonradiative trapassisted recombination, as is the case for MAPbhalides 26,34 .…”