Rationalizing the Effect of Polymer-Controlled Growth of Perovskite Single Crystals on Optoelectronic Properties

Abstract

To improve and modulate the optoelectronic properties of single-crystal (SC) metal halide perovskites (MHPs), significant progress has been achieved. Polymer-assisted techniques are a great approach to control the growth rate of SCs effectively. However, the resultant optoelectrical properties induced by polymers are ambiguous and need to be taken into the consideration. In this study, we have synthesized methylammonium lead triiodide (MAPbI₃) SCs using polyethylene glycol (PEG) and polystyrene (PS) polymers where PEG contains oxygen functionalities and PS does not. We studied the electrical properties of these SCs under dark and illumination conditions. It was observed that PEG-assisted SCs showed few defects with lower photocurrent as compared to the PS-assisted ones because of defect-mediated conductivity. The results are further verified by transient current response, responsivity, and capacitance-frequency measurements. The present study sheds light on the polymer selection for the growth of MHP SCs and their optoelectronic properties.

Figure 1

(a) pXRD patterns and the corresponding (b) fwhm of peaks for as-synthesized SCs. FTIR spectra showing the interaction of (c) PEG with MAI and PbI₂ and (d) PS with MAI and PbI₂. (e) Steady-state PL spectra of the SCs.

Figure 2

I–V characteristics of as-synthesized SCs: (a) semi-log plot under the dark in the forward scan direction, (b) under forward and reverse scan directions in the dark at a scan rate of 100 mV/s, and (c) under light at 0.1 sun illumination; (d) I_photo–P_light plot.

Figure 3

(a) Photocurrent under pulsed illumination at 0.1 sun illumination. (b) Responsivity under different applied biases.

Figure 4

(a) Nyquist spectra and (b) capacitance–frequency spectra under 0.1 sun illumination in the frequency range of 1 MHz to 1 Hz; (c) variation of series resistance as a function of light intensity.