Anisotropic Electric Field Effect on the Photoluminescence of CH₃NH₃PbI₃ Perovskite Sandwiched between Conducting and Insulating Films

Abstract

Photoluminescence (PL) of a nanocrystalline film of methylammonium lead iodide perovskite (MAPbI3) sandwiched between an electrode of a fluorine-doped tin oxide (FTO) layer and an insulating film of poly­(methyl methacrylate) is found to increase and decrease significantly with the application of an external electric field ( F ext), depending on the direction of the applied field, based on the measurements of electrophotoluminescence (E-PL) spectra, i.e., field-induced change in PL spectra. The field-induced change in PL intensity is confirmed to originate from the field-induced change in the number of free carriers which induce radiative recombination, based on temporally resolved E-PL measurements. We propose that an internal field ( F int) exists even without application of F ext. The anisotropic behavior of the effect of F ext on PL is interpreted in terms of a synergy effect of F int and F ext; both fields are additive with the applied field direction from Ag to FTO electrode (positive direction) or subtractive with the opposite applied field direction (negative direction), where FTO is the positive electrode, resulting in an increased or decreased total electric field as well as quenching or enhancement of PL, respectively. The PL lifetime in the nanosecond region increased and decreased with an application of an electric field in the positive and negative directions, respectively, which is attributed to a field-induced change in the concentration of free carriers.

Influence of External Electric Fields on Photoluminescence and Charge Carrier Dynamics of π-Conjugated Polymer P3HT in Multilayer Films with Heterojunctions to TiO2 and Sb2S3

“…In general, the built-in potential exists at the interface of different materials due to the difference of the Fermi energy level. The experimental verification of the internal field has also been reported for many multilayer film devices including P3HT–fullerene bulk heterojunction photovoltaic cells. − We also observed the anisotropy in the carrier dynamics of ammonium lead halide perovskite semiconductor that arises from the internal field due to the built-in potential …”

“…In addition to the steady-state E-PL measurements, we carried out time-resolved E-PL decay measurements with the system reported elsewhere. , The experimental procedure is described in the SI (Figure S3).…”

“…59−61 We also observed the anisotropy in the carrier dynamics of ammonium lead halide perovskite semiconductor that arises from the internal field due to the built-in potential. 34 The actual electric fields that are present in the P3HT film are given by the sum of the externally applied electric field and the internal electric field, if it exists. The internal field may point to the negative direction that is defined in Figure 1 and Figure S1 of the SI.…”

“…In fact, for a methylammonium lead iodide perovskite film, the presence of strong internal fields was suggested from the measurements of steady-state and timeresolved E-PL measurements. 34 In the present study, carrier dynamics of P3HT in the cells with multilayer structures that are relevant to DSSC is discussed. The cells investigated here have different junctions of FTO/TiO 2 /Sb 2 S 3 /P3HT/PMMA/Ag and FTO/TiO 2 / P3HT/PMMA/Ag, where the definitions of the abbreviations will be given in the next section, Experimental Methods.…”

“…Issues on internal electric fields originating from a build-in potential at heterojunctions are also of emerging interest, because they may affect overall efficiency of DSSC. , The investigation of E-PL as a result of the perturbation of external electric fields allows us to gain insight into the internal electric fields in DSSC. In fact, for a methylammonium lead iodide perovskite film, the presence of strong internal fields was suggested from the measurements of steady-state and time-resolved E-PL measurements …”