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

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.We acknowledge financial support from the Engineering and Physical Sciences Research Council of the U.K. (EPSRC). J.M.R. and M.T. thank the Winton Programme for the Physics of Sustainability (University of Cambridge). L.M.P.-O. thanks the Cambridge Home European Scheme for financial support. L.M.P.-O. and J.P.H.R. also thank the Nano Doctoral Training Center (NanoDTC) of the EPSRC for financial support. M.A.-J. thanks Nyak Technology Limited for a PhD scholarship. F.D. acknowledges funding from a Herchel Smith Research Fellowship

High Open-Circuit Voltages in Tin-Rich Low-Bandgap Perovskite-Based Planar Heterojunction Photovoltaics

Low-bandgap CH$_3$NH$_3$(Pb$_x$ Sn$_{1–x}$)I$_3$ (0 ≤ x ≤ 1) hybrid perovskites (e.g., ≈1.5–1.1 eV) demonstrating high surface coverage and superior optoelectronic properties have been fabricated. State-of-the-art photovoltaic (PV) performance is reported with power conversion efficiencies approaching 10% in planar heterojunction architecture with small (100 cm$^2$ V$^{−1}$ s$^{−1}$) intrinsic carrier mobilities.Engineering and Physical Sciences Research Council (Grant ID: EP/M005143/1), India-UK APEX project, Winton Programme (Cambridge) for the Physics of Sustainability, Cambridge Trust, China Scholarship Council, Nava Technology Limited (PhD scholarship), LDRD program, LAN

Research data supporting: "Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling"

This data supports the findings of our publication "Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling". The repository contains transient absorption and transient photoluminescence data as well as fluence dependent photoluminescence quantum yields

Controlling Self-Assembly in Gyroid Terpolymer Films By Solvent Vapor Annealing.

The efficacy with which solvent vapor annealing (SVA) can control block copolymer self-assembly has so far been demonstrated primarily for the simplest class of copolymer, the linear diblock copolymer. Adding a third distinct block-thereby creating a triblock terpolymer-not only provides convenient access to complex continuous network morphologies, particularly the gyroid phases, but also opens up a route toward the fabrication of novel nanoscale devices such as optical metamaterials. Such applications, however, require the generation of well-ordered 3D continuous networks, which in turn requires a detailed understanding of the SVA process in terpolymer network morphologies. Here, in situ grazing-incidence small-angle X-ray scattering (GISAXS) is employed to study the self-assembly of a gyroid-forming triblock terpolymer during SVA, revealing the effects of several key SVA parameters on the morphology, lateral order, and, in particular, its preservation in the dried film. The robustness of the terpolymer gyroid morphology is a key requirement for successful SVA, allowing the exploration of annealing parameters which may enable the generation of films with long-range order, e.g., for optical metamaterial applications.ERC, EPSRC, E

Blue-Green Color Tunable Solution Processable Organolead Chloride-Bromide Mixed Halide Perovskites for Optoelectronic Applications

Solution-processed organo-lead halide perovskites are produced with sharp, color-pure electroluminescence that can be tuned from blue to green region of visible spectrum (425-570 nm). This was accomplished by controlling the halide composition of CH3NH3Pb(BrxCl1-x)3 [0 ≥ x ≥ 1] perovskites. The bandgap and lattice parameters change monotonically with composition. The films possess remarkably sharp band edges and a clean bandgap, with a single optically active phase. These chloride-bromide perovskites can potentially be used in optoelectronic devices like solar cells and light emitting diodes (LEDs). Here we demonstrate high color-purity, tunable LEDs with narrow emission full width at half maxima (FWHM) and low turn on voltages using thin-films of these perovskite materials, including a blue CH3NH3PbCl3 perovskite LED with a narrow emission FWHM of 5 nm