Abstract
AbstractRecombination via subgap trap states is considered a limiting factor in the development of organometal halide perovskite solar cells. Here, the impact of active layer crystallinity on the accumulated charge and open‐circuit voltage (Voc) in solar cells based on methylammonium lead triiodide (CH3NH3PbI3, MAPI) is demonstrated. It is shown that MAPI crystallinity can be systematically tailored by modulating the stoichiometry of the precursor mix, where small quantities of excess methylammonium iodide (MAI) improve crystallinity, increasing device Voc by ≈200 mV. Using in situ differential charging and transient photovoltage measurements, charge density and charge carrier recombination lifetime are determined under operational conditions. Increased Voc is correlated to improved active layer crystallinity and a reduction in the density of trap states in MAPI. Photoluminescence spectroscopy shows that an increase in trap state density correlates with faster carrier trapping and more nonradiative recombination pathways. Fundamental insights into the origin of Voc in perovskite photovoltaics are provided and it is demonstrated why highly crystalline perovskite films are paramount for high‐performance devices.
Highlights
The power conversion efficiencies (PCEs) impact of active layer crystallinity on the accumulated charge and opencircuit voltage (Voc) in solar cells based on methylammonium lead triiodide (CH3NH3PbI3, MAPI) is demonstrated
Photo luminescence spectroscopy shows that an increase in trap state density of state-of-the-art solar cells based on organometal halide perovskite solar cells (PSCs) have already exceed 22%,[1]
We have identified decrease in MAPI crystallinity as an origin of Voc losses in perovskite solar cells
Summary
The power conversion efficiencies (PCEs) impact of active layer crystallinity on the accumulated charge and opencircuit voltage (Voc) in solar cells based on methylammonium lead triiodide (CH3NH3PbI3, MAPI) is demonstrated. Photo luminescence spectroscopy shows that an increase in trap state density of state-of-the-art solar cells based on organometal halide perovskite solar cells (PSCs) have already exceed 22%,[1]. Such progress is closely associated with improvement of their open-circuit voltage (Voc).[2] To date, impressive device Voc values, exceeding 1.2 V, have been achieved for PSCs with an optical bandgap (Eg) of 1.6 eV.[3] the photovoltages demonstrated do not yet reach the radiative efficiency limit.[4] Further reducing nonradiative photovoltage loss, either in the bulk active layer or at intercorrelates with faster carrier trapping and more nonradiative recombination pathways. I.e., p–i–n architectures, comprising poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) as bottom
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