Nonplanar Spray-Coated Perovskite Solar Cells

Abstract

Spray coating is an industrially mature technique used to deposit thin films that combines high throughput with the ability to coat nonplanar surfaces. Here, we explore the use of ultrasonic spray coating to fabricate perovskite solar cells (PSCs) over rigid, nonplanar surfaces without problems caused by solution dewetting and subsequent "run-off". Encouragingly, we find that PSCs can be spray-coated using our processes onto glass substrates held at angles of inclination up to 45° away from the horizontal, with such devices having comparable power conversion efficiencies (up to 18.3%) to those spray-cast onto horizontal substrates. Having established that our process can be used to create PSCs on surfaces that are not horizontal, we fabricate devices over a convex glass substrate, with devices having a maximum power conversion efficiency of 12.5%. To our best knowledge, this study represents the first demonstration of a rigid, curved perovskite solar cell. The integration of perovskite photovoltaics onto curved surfaces will likely find direct applications in the aerospace and automotive sectors.

Keywords: air knife; curved solar cells; integrated photovoltaics; perovskite solar cells; scalable fabrication; ultrasonic spray coating.

Figure 1

Schematic representation of the experimental setup. Part (a) depicts the standard geometry for spray coating a horizontal substrate, part (b) shows spray coating an inclined substrate, and part (c) shows spray coating a curved substrate. In parts (a) and (c), the spray-head speed is ν_o, while in part (b) it is reduced to ν_ocos(θ), where θ is the substrate inclination angle as shown. An air knife used to induce perovskite nucleation is not shown in this figure but can be seen in the schematic shown in Figure S1.

Figure 2

Box-plot summary for the key reverse sweep device metrics recorded as a function of inclination angle.

Figure 3

Part (a) shows the current–voltage characteristics of a champion device fabricated at an inclination angle of 30° (metrics derived from reverse sweep), with its stabilized power output (SPO) at a voltage close to the maximum power point recorded over 1 min shown in part (b). The inset in part (b) is an image of a typical series of device pixels deposited on a 15 mm × 20 mm substrate.

Figure 4

XRD diffractograms as a function of the deposition angle.

Figure 5

SEM images for perovskite films deposited at increasing angles of inclination. Parts (a–e) represent perovskite films deposited on surfaces held flat and at 15, 30, 45, and 60° away from the horizontal, respectively. Note the presence of submicron pores in part (e), 3 μm scale bar inset.

Figure 6

Part (a) shows an image of a fully sprayed perovskite solar cell on a curved rigid substrate, (b) shows the same device in profile to illustrate curvature, (c) box plot summary of key performance metrics, (d) represents JV data for the best performing cell (metrics derived from reverse sweep), (e) details results of a stabilized measurement carried out near the maximum power point for 60 s.